The Tangles of Neaera's Hair

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[January 21, 2012]

I posted an edited version of the flight test video here. The quality is not very good -- I need to get a newer spy camera -- but the general impressions are clear enough.

[January 20, 2012]

Yesterday I attached a little video camera to the left boarding step to find out how well my gear doors are closing. The last time I tried to do this, several years ago, the step strut vibrated so violently, and at just the right frequency, that the set screw holding the lens in the camera backed out and the lens disappeared shortly after takeoff. The strut is rectangular in section, and vibrations like that are usually due to vortices being shed from alternate sides in rapid succession. This time, I made an airfoil-shaped fairing around the strut with foam and aluminum tape. It still vibrated, but not to the point of dismantling the camera (for which I got a new lens). I was also interested in observing the behavior of the left main landing gear strut, since I have become convinced -- actually, it is obvious, now that the scales have fallen from my eyes -- that the "slumping strut" problem was not a slumping strut at all, but rather a sticking, and perhaps slightly overinflated, strut on the opposite side. The test consisted of a single flight around the pattern, with the downwind leg extended about three miles so that I could accelerate to cruising speed.

As far as the landing gear doors are concerned, the camera could see only the left and nose gear doors; I will have to put the camera on the other side to see the right doors. After retraction and during initial climb, the doors are not perfectly closed, but they are satisfactory; at 145 kias, which would be a typical indicated airspeed at cruise, they bulge out slightly. The worst gap, around 3/8 of an inch, is at the lower half of the outer door, which seems to flex outward. It is a simple 1/4-inch thick sandwich of carbon and glass; I could stiffen it with some simple ribs. I doubt that the drag penalty is very great, but I would like the doors to shut nicely for aesthetic reasons at the very least.

As for the strut, it was interesting to see that the left main seemed to remain somewhat overextended for a long time after touchdown. On seeing the tape, it struck me that this problem, which began to manifest itself about a year and a half ago, might be related to the flaps, which relieve the weight on the gear after landing. Furthermore, to reduce lift I usually move the stick forward once the nose gear has touched the ground; this, too, has the effect of lifting the tail and slightly relieving the main gear loads. I also am in the habit of braking rather hard, because I like to turn off at the taxiway that leads to my hangar and not have to back-taxi to it; and hard braking puts a load on the strut that increases friction and makes it move less freely. It seems as though the solution to this problem might be some combination of 1) carefully ensuring that the main struts are equally inflated; 2) retracting the flap during roll-out; 3) not braking harder than necessary; and 4) not pushing the stick forward during roll-out.

[January 14, 2012]

Jon Karkow pointed me to a Piper owners' forum where there was a discussion of slumping struts on Cherokees. So it turns out this problem is not confined to me. Participants gave various explanations, one suggesting that the problem is not the right strut collapsing, it's the left strut remaining excessively extended after landing because of "stiction" or starting friction (which is greater than sliding friction). So maybe I need to overhaul the left strut as well.

[January 11, 2012]

Shot a coupled ILS approach to Van Nuys; very calm day, and it worked nicely. Then I returned to Whiteman and landed, and to my amazement and very great disappointment as I turned left off the runway the right strut compressed in the same way as before I overhauled it. Complete bafflement.

[January 6, 2012]

With much spillage, since I did not have a proper funnel and was pouring from a 1-quart can into a 3/8-inch hole, I got the oleo filled to something like the proper height with hydraulic fluid and reinstalled it in the airplane. Now I just have to understand why having too much fluid and not enough air in it was having the observed effect. I cleaned and repacked the wheel bearings while I was at it. It's never clear to me why this is necessary; a car goes tens of thousands of miles between wheel bearing services; an airplane rolls only a few miles a year.

[January 5, 2012]

Nothing was wrong inside the oleo. The cause of the problem has to be an incorrect amount of hydraulic fluid. I moved the air valves when I modified the PA28R struts for Melmoth, and so can't use the Piper method for adding fluid, which involves overfilling and then compressing the strut to force excess fluid out the air valve. The problem is that without the air valve being in its original position, about two inches below the top of the cylinder, there is no convenient way to set the height of hydraulic fluid inside the strut. There is an inconvenient way; a 1/8" pipe thread plug in the top of the strut can be removed, and fluid sucked out through a straw, as it were, to the proper depth; or a special terporary plug could be inserted with a tube extending two inches into the strut, and the strut filled, extended, and then re-compressed, forcing fluid out that tube and preserving the proper amount of air in the strut. Unfortunately, this top plug is inaccessible when the strut is in the wing. I guess I could drill a hole in the skin above the strut to get at it. Another possibility would be to take the air valve and insert a bent tube of the proper length with which to suck out excess fluid; but I'm not sure there is room inside the oleo to feed in a bent tube at that location. Another possibility would be measurement: determine the volume of hydraulic fluid required to fill the strut, and put in just that amount. That, however, would require completely emptying the strut to start with, and that can be done only by removing the piston from the cylinder -- possible, again, but not exactly convenient. Fortunately, the oleos hold air and fluid indefinitely, and so replenishment is a rare event. For the time being, I will do nothing, since with the strut out of the airplane I can remove the top plug and get the fluid level right.

[January 4, 2012]

I took the right main strut off the plane today to overhaul it and perhaps to discover the cause of its strange tendency to compress on turning left off the runway after landing and then gradually to re-extend while taxiing. The fluid was very dirty, but apart from that the condition of the inside of the oleo was unremarkable. There was some superficial corrosion on the unpainted, exposed top of the cylinder; not bad, considering that this strut was assembled more than 20 years ago. I'll clean it up and chromate or alodine the exposed parts before re-assembly. I bought two rebuild kits in order to motivate myself to overhaul the right strut as well, but I did partly dismantle it and replace a couple of O-rings just a few years ago and so I will probably end up stockpiling the rebuild kit until the right strut begins to act up.

[December 20, 2011]

For some time now I have not left the battery tenders continuously connected to the batteries, and the battery water level has stayed put, surpporting my suspicion that the water had been evaporating not because the batteries were too hot in flight, but because they were too warm during the much longer periods spent parked in the hangar. I have searched in vain on line for mention of battery tenders cooking away battery water (or of my specific type -- the brand name is Schumacher, I believe -- doing so) and have not found anything.

My hope of getting the intake manifold modification done during November was vain; the month came and went without much being accomplished, and now, in the most accomplishment-free month of the year, nothing will get done until January. I have been studying drawings of the engine and trying to figure how how best to route the 2-inch tubes running from the throttle body to the log manifolds. The problem is how to get around the oil filler neck on one side and the starter motor mounting flange on the other, while keeping the two branches mirror images of one another. No doubt there is an infinity of possible solutions, serpentine or tortuous in various degrees, but whatever combination of bends I come up with I have to be able to describe to the tube bender with a reasonable confidence of his producing usable parts.

Mike Melvill came down to have lunch with me and our friend Jerry Slocum, who was in LA for a few hours on his way back to Salt Lake from a pleasure cruise through the Panama Canal. (Jerry used to go with me in Melmoth 1, many a Wednesday during the late '70s and early '80s, to lunch with Burt Rutan and a few other friends at Reno's cafe at Mojave; he always ordered a patty melt.) Mike's Long-EZ is very well equipped, including WAAS and an Aspen PFD, and we talked about the extreme accuracy of GPS approaches, plus or minus half a meter, and how you could probably make a hard but non-damaging landing in zero-zero conditions, if you had to, hands off, using the coupled autopilot. (Airlines do this all the time; as Jerry pointed out, we have probably all ridden along during practice autoland landings without ever knowing it.) I suggested that the addition of a rangefinder from a camera could provide you with height information as you neared the runway, and you could even manage a flare of sorts. Actually, I think that perhaps modern cameras focus digitally, by looking for sharp edges, rather than by ultrasonic pinging; but our discussion reminded me of the ultrasonic rangefinder I bought a few months ago (for $30) when I was thinking about experimenting with it as a non-aerodynamic way of measuring airspeed. Unfortunately the thing came with no guidance whatever about how actually to use it; it was assumed that the sort of electronic hobbyist who would buy it would know what to do with it. Not me. And now, alas, Paul Lipps has died.

[December 9, 2011]

I made the gadget to turn the oxygen on and off. It pulls the 3/32 cable 2.25 inches, locks overcenter, and when unlatched it releases the cable and a spring closes the bottle valve. The reason for this arrangement, rather than a simple solenoid, was concern that the rapid, powerful action of a solenoid might eventually damage the valve seat. The handle is on the left sidewall, by the pilot's seat.

The outlets (there are just two) are between the front and rear seats, on the centerline.

Today I sawed off the leaking fitting (called a "cone") on the 3/16-inch ox line from the bottle to the manifold (visible here) and spent a couple of hours struggling to put on a new one. I tried silver solder, then regular solder, and finally called my friend Homer Knapp, who was stuck in traffic somewhere in Westwood but remained on the phone (it's illegal to use a cell phone while driving here) long enough to tell me that I needed to get some white paste flux at a welding supply store. You'd think I would know stuff like that, but no. Airplanes don't call for a lot of silver soldering or brazing. It was 4:45, getting dark, but there's a welding supply store across the road from the airport (it's where I get my "aviator's breathing oxygen" at a deep discount) and I got some there. It worked like a charm. Actually, super glue would probably have been good enough; the force trying to separate the fitting from the copper line at 2,000 psi is about 81 pounds. Anyway, I'll re-install that on Monday and then the oxygen system will be well and truly done.

The next step will be to determine whether the unpressurized Bendix mags will work at 17,500 feet -- they will probably start arcing -- and then to decide whether to get pressurization kits for them or to install my pressurized Slicks instead.

[November 21, 2011]

I collected some data on speeds and fuel flows at very low power settings. At a density altitude of 7,000 feet and a weight of around 2,000 pounds, I set the rpm at 1,800 and did a sweep of manifold pressures from 17 to 25 in. Hg. with extremely lean mixtures. Below 24 in. Hg there was very little variation. At 17/1800 IAS was 90 kt for a TAS of 100.5 and fuel flow of 3.65 gph. The increase in fuel flow was more or less linear with manifold pressure up to 24 inches and 4.9 gph, where the TAS was 128 kt. Nmpg fluctuated randomly between 26 and 27, reflecting both the flatness of the mileage curve at low speeds and the difficulty of getting precise measurements. Above 5 gph the curve becomes steeper, in part because you have to increase rpm; 28/2300 gives 150 kias, 167 ktas, and 8.8 gph (18.9 nmpg).

[November 19, 2011]

The oxygen system is now working. It took me a while just to decide where to put the pressure gauge (it's in the floor between the seats, alongside the outlets), how to route the 1/8-inch aluminum line connecting it to the bottle, and where to put the pilot's end of the cord that turns the bottle valve on and off. As far as the cord was concerned, I was originally planning to put it with the outlets and the gauge. That would have involved several bends and two or three pulleys. I then experimented with various tortuous paths up the left sidewall before discovering that there is a perfectly straight line from the pulley at the bottle (see picture below) to a point on the left sidewall beside the pilot; it requires no pulleys, interferes with nothing, and is hidden by the existing armrests. Now I have to decide whether I should just put a loop in the end of the cord and bond some sort of miniature coathook to the sidewall, or whether I should go to the trouble of making an overcenter lever to turn the oxygen on and off. I will almost certainly do the latter -- eventually. The plumbing uses a mix of flare and compression fittings and a third type, whose name I don't know, that consists of a hemispherical male element brazed or silver-soldered to a copper or steel tube and a bowl-shaped female receptacle. I first tried flares on the 1/8-inch 3003 aluminum tube; they leaked at both ends. I replaced one with a brass compression fitting; it worked fine on the first try. I wanted to replace the other flare with a similar fitting, but couldn't find one; but I eventually got the flare to seal. Now the only leak, and it is very slow, is at the brazed fitting on the short 1/4-inch copper tube between the bottle and the manifold, visible in the picture below. The male fitting is visibly deformed; I need to remove it and braze on a new one.

The choice of aluminum for the pressure-gauge line was based on weight; copper or steel would be more conventional. The tubing has a wall thickness of .025 in. It is officially rated for pressures up to 2,300 psi, but the tensile strength of 3003-O aluminum is 16,000 psi. Since the bore (0.075 in.) is 1.5 times the total wall (0.025 + 0.025), the tensile stress at the maximum bottle pressure of 2,000 psi is 3,000 psi and the margin of safety is over 5. I think that the reason harder metals are usually used is to resist wear and tear; the aluminum tube does look pretty easy to damage. It is in a protected location, however, and I think I will be able to avoid dinging it. Time will tell.

[November 7, 2011]

Today I flew around for half an hour at 5,000 feet with the engine cranked back to 24/1900, which yielded 5.4 gph or about 30% power. This gave a true airspeed of 130 knots and a specific range (ie gas mileage) of 24 nmpg (around 27.7 smpg). It seems that the airplane falls short of its computed performance at high power, but exceeds it at low. This suggests that the value of e, which is essentially a way of saying what the effective aspect ratio of the wing is, is higher than the computer makes it. In other words, parasite drag is higher than the computer thinks, and induced drag is lower. But it could also mean that the engine's specific fuel consumption (pounds of fuel per horsepower per hour) at low power settings is lower than the computer thinks, or for that matter that the fuel flow instrumentation is not accurate and its errors are non-linear.

The conventional wisdom is that the real best-range speed tends to be higher than the theoretical one because engines are inefficient at low power settings. The next time I fly without a destination, I'll see if I can generate an empirical specific-range curve.

I have been working a couple of hours a day on a system for turning the oxygen on and off from the pilot's seat. The oxygen bottle is in the baggage compartment, wedged under the rear seat footrest (the rear seats face aft). Here is the apparatus, temporarily mocked up with some random twine and fittings.

The fine safety wire securing the pulley is actually not a mockup. It is the final arrangement, and is simply the lightest way I could think of to hold the pulley. It is anchored with a stainless steel cotter key whose legs have been bent outward and trapped under a phenolic disk bonded to the inner skin of the fuselage. I guess I am trying to save a gram here and there to make up for the weight of the oxygen bottle. One oddity is that the bellcrank that operates the bottle's on-off valve has to be at a certain angle, which ends up clocking the bottle so that its built-in pressure gauge faces the floor. I will have to glue a small mirror to the floor to read it. There will, however, be a second gauge in the cabin that the pilot can see.

[October 29, 2011]

The lubrication of the pitch trim mechanism on the 4th was miraculously effective. I have still not flown high enough, nor in cold enough weather, to know whether this new lubricant (which my old friend and onetime Flying Magazine editor Stephan Wilkinson, a former car buff who would get waxes and greases for his yellow Porsche from Germany, recommended and in fact caused to be shipped to me) will stiffen up unacceptably like the last one I tried. Perhaps not; when I put it into the freezer it got somewhat stiffer, but not excessively so. Anyway, now the operation of the trim is positively silky; I feel like changing speed just for an opportunity to use it.

As a first tiny step in the project of reversing the intake manifold, I rotated the vacuum pump 90 degrees in order that its outlet not interfere with the throttle body, which will be above it. I think I will do the manifold modification during November, which is when I have to do my annual inspection anyway.

Yesterday I flew around for 40 minutes just to exercise the plane a bit. When I do this I run about 25 in. Hg and 2,000 rpm with a fuel flow of 6.5 gph at about 5,000 feet d.a. I noticed that my airspeed was 20 times the fuel flow. This puzzled me at first, since that is also the case at my usual cruising setup (170 knots at 8.5 gph) and it ought not to be true at two widely different speeds. It later dawned on me that one (the faster) is true airspeed and the other is indicated. So, in car-compatible terms, it's actually 23 mpg at 195 mph and 25 mpg at 160 mph -- just like our 1986 Camry, but faster.

[October 6, 2011]

I need to remind myself, whenever I'm dreaming up exotic theories to account for electrical malfunctions, to repeat several times, "Bad ground." After taking lots of measurements, all of which checked out fine, I discovered that the fuel gauges worked when I held the piece of the panel that contains them in my hand, but stopped working when I put it back into the airplane. It turned out that moving the wire loom made the problem appear and disappear. Since it affected both gauges equally, it had to be a ground issue -- I believe that is the only wire they have in common. I didn't find the bad connection, but with a couple of tiewraps I stabilized the loom so that the problem went away. There are some malfunctions -- such as the weird noise our dryer is currently making -- that are very difficult to diagnose, but become easy once the failure is complete. I will wait for the fuel gauges (and the dryer) to fail completely.

A huge bubble turned up in the #2 flap actuator circuit yesterday, fortunately on the ground. It may have had some connection with my overhauling the #2 master cylinder in August; why it waited this long to announce itself, I can't say. The hydraulic flap actuation system has been by far the most troublesome thing on the airplane, and I still don't understand some of the things it does. Most of the time it works just fine, but it continues to be plagued with minor leaks and occasional major misbehaviors. Not ready for certification.

[October 4, 2011]

My theory that the high breakout friction in the pitch trim circuit was due to thrust on the jackscrew bushing proved to be incorrect. It was just general dirt and lack of lubrication. I had removed all lubricants a while ago, thinking that they were stiffening up at high altitude and low temperature and making the trim hard to operate. This time I tried a new type of lubricant. I then brought the trim mechanism, which I had removed from the airplane, home and put it in the freezer for a few hours. It was stiffer, but still worked smoothly. So in the end I lubricated everything and put it back together. It feels nice now, but I haven't tried it in flight yet. Another theory of mine, that the weird behavior of my fuel gauges was due to failure of some zener diodes in an interfacing circuit board, also bit the dust. I got the circuit board out and tested the diodes, and they all seemed to be regulating to 7.15 volts, just as they're supposed to do.

[October 1, 2011]

On Wednesday I flew to Santa Rosa to have a look at the participants in the NASA/Google/CAFE Green Flight Challenge. Prizes totaling more than 1.6 million dollars are offered for the most efficient airplane, the minimum standard being 200 passenger-miles per gallon over 200 miles in two hours or less. This is not a very demanding standard if no constraint is placed upon wingspan. Heck, Melmoth 2 with four aboard already gets 100 passenger miles per gallon, and it's optimized for speed, not efficiency. Participation was limited to 18 entrants, but in the event only four were ready. One of these, a powered sailplane modified by Embry-Riddle with a 75-foot-wing and a supplemental electric motor, was disqualified because the university refused to insure its participation in what passed for an "air race." Fallout from Reno. A two-seat Phoenix motorglider of 44-foot span had no realistic chance against the other two, both pure-electric designs of extremely long span and high aspect ratio. So in effect there were only two contestants. The larger of these, the Pipistrel Taurus G4, consisted of two two-seat Taurus sailplanes joined, Twin Mustang fashion, to a centersection carrying half a ton of batteries and a 195-hp electric motor. Here it is in flight:

I am inclined to think it will win, simply by dint of having four seats, not that a wingspan of nearly 70 feet hurts. As was the case in the old CAFE races, unreasonable emphasis is placed by the scoring formula on passenger capacity, even though private airplanes seldom fly with all seats full. Peter Lert, who with Gene Sheehan won the first CAFE race in a Quickie Q2, is fond of pointing out that an even better score could have been achieved by a full DC-3, and meals could have been included. The only registered entrant with more than four seats was the bio-diesel powered Synergy, but I doubt that the claims made for its very complicated arrangement of flying surfaces would have been borne out in practice. In any case, it didn't show up. What this contest is going to demonstrate, apart from the fact that most people can't finish a job in time even for a million bucks, is that 200-pmpg airplanes can't fit in taxiways, hangars or tiedowns.

Winners will be announced on Monday.

No trip would be complete without one or two things going wrong. I observed that there is a slow fuel leak where the left outboard flap track bolts to a rib. That should be easy to fix. The fuel gauges, all four of them, have stopped working, and now indicate full at all times. This has to be a problem with the circuit board that provides an interface between the float-type senders and the edgewise voltmeters that I use as gauges. Finally, there is unacceptable breakout friction in the pitch trim circuit at cruising speed. This is nothing new, but I am finally going to try to do something about it. I think it will require replacing the bronze bushing that currently serves as a thrust bearing for the trim jackscrew with a ball bearing.

[September 25, 2011]

After two and a half years or so, a buyer appeared for Ray Henning's beautiful T-18. Ray came down from Seattle for the handover, and I flew up to Tehachapi to see him. It was overcast in the Basin, and I had to hold for about half an hour waiting for a clearance to VFR on top from Burbank. The #3 (center right) CHT went to the top of the green. This is a problem: at the start of the takeoff roll, power is high but speed is low, and so CHTs rise rapidly. If a cylinder is already at the top of the green, it's going to climb out of the green before its temperature begins to drop again. I could not detect any difference in the engine after this episode, so I suppose it did no damage, but an airplane, like a car, ought to be able to idle indefinitely. I am hoping that my scheme of reversing the intake manifold will improve airflow through the cowling by removing the portion of the intake manifold that obstructs the exits. It should also eliminate the problem of rough idling after long holds, which is due to the throttle body, which is the only portion of the fuel system still on the hot side of the baffles, becoming heat-soaked.

[September 21, 2011]

Some friends brought their children over to the hangar to show them the plane. The cockpit miraculously survived having a couple of 6-year-olds sit in it for a few minutes. I then flew around the pattern to show them what it looked like in the air. I offered to take someone along with me, but all declined. The phrase "fiery crash" was uttered several times. Nevertheless, the 3-minute flight was without incident.

[September 19, 2011]

Nancy and I went to Cape Cod on August 26 and returned this last weekend. Melmoth stayed behind, so there has been nothing to report. Before we left, however, I did overhaul the #2 flap master cylinder. My impression that it was leaking through the hollow piston shaft proved to be wrong. I could not find an obvious leak, but I suspected that an insufficiently chamfered hole near the end of the shaft, where a clevis pin passes through it, may have damaged the small (3/8" I.D.) O-ring during assembly. I enlarged the chamfer and polished it vigorously, and also polished out some small scratches and dings in the piston shaft that I had evidently overlooked (or considered inconsequential) when I first installed the system. I did fly the day before we left, and the cylinder seemed no longer to be leaking. But it is too early to be sure.

There was a leak in the static plumbing after I modified it. I eventually located and repaired it, and also added a drainable trap just forward of the right static port. At present it ends with a flare cap, but I should probably replace that with a quick-drain.

I spent a good deal of idle beach time at the Cape face-down in the sand, thinking about reversing the intake manifold. I am determined to do it, even though I suspect that it may turn out to be one of those big modifications that yield no detectable benefit.

[August 17, 2011]

Something worth noticing in the photograph below is that the ridge on the back of the static port is above center. This is not just sloppy work. The hole on the other side is in the center of the disk, but it is drilled at an angle -- all part of my apparently doomed effort to keep water from getting into the static plumbing.

I tried wrapping the #1 cylinder exhaust with the thought that the insulation might keep heated air from entering the baffles. It seemed to have no effect at all. In fact, since the pipe and the head are in intimate contact, I'm not sure that making the pipe hotter is the best way to make the head cooler. I observed that the #3 cylinder is only 10 degrees C. below the #1 -- but 25 to 35 above the others -- so maybe the problem, if it really is a problem, is not related to the rearmost cylinder's baffle. This is all really academic; all temperatures are well within the green. I would just like it if they were all the same.

I decided to get serious about the hydraulic leaks in the flap synchronizer. It's not possible to properly simulate air loads on the flap while on the ground, so I took out the floor panel that normally covers the synchronizer and watched the cylinders as I cycled the flaps in flight. The first leak I found was in the #2 master cylinder; fluid seems to be seeping out through the hollow stainless steel piston shaft. That should be easy to fix by simply pressing in an aluminum plug.

[August 13, 2011]

One chronic annoyance has been the proneness of the static system to take on water while parked during heavy rain. I'm surprised this can happen, since the ports are so tiny and are on essentially vertical surfaces, but anyway, it happens, and happened again at Oshkosh, where it was apparent to me as I took off that I was not getting a reliable airspeed indication. On the assumption that the basic problem was that I had thoughtlessly put a downhill segment of static tube from the right-hand port, I revised the plumbing thus:

The picture shows the inside of the right-hand wall of the baggage compartment. The tubing is 3/16-inch aluminum; the joints are made by sliding a 1/4-inch o.d. sleeve over them and sealing with JB Weld. The static port is the round thing; it's about the size of a quarter.

After buying a new alternator for more than $600 a couple of weeks ago, today I found a spare alternator in my hangar -- in the box where I stored it 30 years ago.

[August 7, 2011]

In mid-July I had a visit from Francois Besse, the editor of the French magazine Piloter. We had a brief flight -- the intention was to go to Santa Paula for lunch, but we turned back when I saw that the alternator was not charging -- at the end of which he took this nice picture on short final at Whiteman.

He complained about the reflection in the windshield of the gray area above the panel. I guess he has a point. The ceiling speaker has been derided as a quaint anachronism. Indeed, I have never used it.

[August 1, 2011]

I always feel some anxiety before leaving on a long trip, not because of the dangers of flying, but because I worry that something on the airplane will break in some godforsaken place and I will spend days in a state of intense impatience and boredom getting it fixed, while having to eat at restaurants that serve you too much meat and potatoes but no vegetables. Is this some new culinary fashion in the central United States, intended, perhaps, to hasten the general trend toward grotesque obesity? Worse, this dismal experience would cost a lot of money.

Luckily, none of that came to pass. The plane did fine, except for some flaky behavior on the part of my main gear struts, which don't seem to want to stay equally inflated. I really need to overhaul them -- not a difficult job: just disassemble, replace O-rings and reassemble. The engine used one quart of oil in 20 hours, and the oil mist on the windshield ceased toward the end of the trip, making me think that when it's comparatively heavy it's because the plane has been sitting and what's ending up on the windshield is the accumulated drips of several days. And the final version of the pilot's seat was comfortable for long flights. So that was all good.

Oddly, when we flew to Japan, Europe and Chile in the old Melmoth, I never worried about anything breaking. Youth!

There were some minor glitches. The halogen flashers are working fine, but I don't dare use them on the ground because they seem to overheat the lenses. The right nav light bulb burned out. The static source was briefly unreliable after heavy rain; I need to reroute the lines to eliminate a downhill segment immediately adjacent to the starboard port (though it seems amazing that any water at all can get into those tiny holes). I suspect that the air inlet that I added to the right lower cowling to cool the battery box -- it looks like a little machine gun port -- is actually behaving as an outlet, because the ram pressure in the cowling is higher than the pressure at the inlet face, which is down in the boundary layer. I intend to eliminate that inlet and take in battery cooling air directly from the lower plenum.

I am puzzled that while with the old voltage regulator the ammeter would indicate zero once the battery was recharged after startup, with the new one it seems to indicate around +5 amps all the time. The ammeter is wired to show charging current, not bus load, so this is unexpected. It could be that it is happening because the old regulator was set for 27 volts and this one is set for 28, and the Yuasa motorcycle batteries somehow prefer a slightly lower voltage. I struggled with this problem years ago and resolved it by adjusting the system voltage downward from 28 volts; I guess I just need to do the same again.

As was the case last year, I enjoyed tailwinds eastbound and part of the return trip, and when there were headwinds -- in Wisconsin and Iowa on Saturday -- they were mild. I had to work around some big thunderstorms near Las Vegas, New Mexico, but generally didn't need to deviate much from the GPS-coupled straight line. True airspeeds conformed closely to the Melmoth 2 Rule: 20 knots per gallon per hour. I generally cruised at around 8.5 gph and 170 ktas. Early in the trip I flew a long stretch at 15,500 and found that I could maintain good oxygen saturation -- around 93 or 94% -- with the Nelson meter just barely cracked, indicating well below 1 liter per minute.

[July 31, 2011]

The new alternator and regulator having been installed, I left for Oshkosh on the 26th, a day later than planned. I refueled in Salina, Kansas after a 6+15 flight, and continued to Prairie du Chien, at the confluence of the Wisconsin and Mississippi rivers, where I RON'd. I scud-ran in marginal 1,000-and-1 conditions into OSH the next morning. I left Saturday before noon, got fuel at Prairie du Chien (I was too impatient to wait for the OSH fuel truck, even though their gas was way cheaper, and the people at PDC were nice) and flew another 6+15 leg to Gallup, NM, where I slept. Airborne at the crack of dawn, I made it almost into LA before encountering, just west of Palmdale, rain so heavy that it took the paint off the leading edges of my empennage. About 20 hours for the round trip, and almost $1,200 worth of fuel. This can't go on much longer.

[July 22, 2011]

The full field test, which consisted of disconnecting the regulator and jumping the alternator output to the field post, so that the alternator simply bootstrapped without regulation, produced no charging voltage. I removed the alternator again -- now that I knew how to do it, it took only ten minutes and drew no blood -- and opened it up. I found much of the stator winding blackened from excessive heat.

It is still not clear to me what exactly had failed, but the thing looked ugly enough that it seemed best to retire it and get a new one. It had, after all, lasted for about 1,500 hours of flying over a period of 34 years. What I think produced the heat damage was not the first thousand hours of its life in Melmoth 1. There it was cooled with a blast tube. In Melmoth 2, reasoning that it was now on the cold side of the baffles, I omitted any provision for active cooling. I should have provided it with a reverse blast tube -- that is, a vent to the low-pressure side of the baffles. The current version has a built-in fan; no blast tube is required to make air flow through it.

Mark, the foreman at Able Air, tried to locate a replacement, but the only one we could come up with was at Aero Accessories in Van Nuys, and the owner there had taken the day off and would not be back until Monday. My big worry now is that the new alternator will prove to be incompatible with the regulator I just bought. After that, I believe I will have run out of things to go wrong.

[July 21, 2011]

Quel mess. I installed the Cessna regulator -- this involved quite a lot of new wiring -- and then proceeded to damage it by stupidly attaching a ground lead to what I believed was a ground post, but was really A+. Melted some perfectly good wire. I thought I had damaged the alternator too, so I took it off -- a hideous job, even though there are only three bolts; they are in the most inaccessible locations imaginable -- and took it over to an aircraft accessory overhaul shop at Van Nuys. The guy put it on his testing machine and said it was OK, although the Woodruff key in the drive gear needed to be replaced. This he did, for a modest $20. I learned that my alternator, which I have had for around 35 years, is obsolete and no longer supported, so if it's dead I have to get a replacement. Since I do not have a core to trade for it, this could turn out to be pretty expensive.

I put the alternator back on the plane -- an even worse torment than taking it off, almost two hours, with considerable bloodshed -- and ordered a B&C regulator, which came this morning. Parenthetically, I love the amazing promptness with which stuff you order on line is delivered. This regulator had a completely different wiring hookup from either of the previous ones, plus a different mounting bolt pattern. I spent this afternoon hooking it up temporarily, only to see no charge. Tomorrow I have to do a "full field" test, which involves bypassing the regulator and letting the alternator self-regulate in response to changing rpm. There is a lot of advice on line about troubleshooting charging systems, and my system has so for been more or less within limits, except when it comes to actually putting out some voltage. Quite a puzzle.

[July 14, 2011]

On this moderately happy Bastille Day I found in one of the midden heaps in my hangar a Cessna voltage regulator.

Its wires outnumber the ones on my present regulator by three, and I do not have the pinout for it, but a local FBO offered to let me look through his old maintenance manuals to figure it out. He said this unit contains an overvoltage relay, overvoltage warning light circuitry, etc., so that is what the other wires are about. Naturally it does not have the same footprint or attachment hole spacing as the old Motorola one, but I can work around that. Of course, for all I know it is burned out or soon will be. The Motorola lasted 38 years and 2,500 hours -- not bad for a cheap non-aircraft-quality part.

Russ Hardwick, with whom I had lunch today, brought me a couple of very bright LEDs, three or four of which, in series, would do nicely for panel lights, running on the 12-volt bus, which consists of the 1-amp output from an ancient Narco voltage reducer. At present I think the only load on it is the GPS. Russ seemed to think that if I wanted more 12-volt current I could tap 12 volts off the middle of my pair of batteries; he suspected that batteries work on Communist principles: from each according to his ability, to each according to his need. That might work for batteries; it certainly wouldn't for people. At any rate, the LEDs draw almost no current, so I think the Narco will handle them fine.

[July 13, 2011]

Took off for Santa Paula with Francois Besse, the visiting editor of a French aviation magazine. We hadn't gotten very far when I noticed that the alternator was not charging, and we turned back. After some troubleshooting I concluded that the voltage regulator had failed. It is a little Motorola unit that I believe was used on some trucks that have 24-volt electrical systems. I must have gotten it almost 40 years ago. Online I found physically similar ones on offer from a Chinese firm, but only if I wanted to buy 500 or more. It looks as if I may have to get a different regulator and rig up a new mount for it. Spruce has a couple that incorporate overvoltage protection, something neither Melmoth has ever had.

[July 12, 2011]

The countdown to departure for Oshkosh has begun. Or, to put it a little less portentously, I started doing a lot of deferred maintenance. I installed the small SkyTec starter, which is not that small, or light, any more, but which will clear the intake manifold when I turn the latter around. I greased the landing gear retraction joints. I found and fixed a loose Cannon plug on the oil temperature sensor; it was probably responsible for the fluctuating oil temperatures I've been seeing lately. (Fluctuating oil pressure can be a dire symptom, but fluctuating temperature is almost certainly an instrumentation problem.) I continued my still unsuccessful search for the source of a pretty sizeable hydraulic fluid leak at the right outboard actuator. I replenished the hydraulic fluid reservoir, which was significantly depleted after just ten hours of flying. There are still leaks in several places. I cleaned the windshield, which had more oil spray than usual on it, and carefully inspected the engine without finding any new oil leaks. The oil on the windshield is a nuisance, but it is actually not very much oil, since the engine is still going 15 hours or so on a quart. I now need to put the plane on jacks, swing the gear, make sure all the doors are closing properly, and regrease the wheel bearings. It's pretty clear that I won't have the remote control for the oxygen bottle valve, or the remote oxygen pressure indicator, installed before I go, because I have other things to do than work on the plane. But at least I will have oxygen.

[July 2, 2011]

A correspondent, Ryan Niederkohr, explained the apparent inconsistencies in the results of my oxygen experiments of last week. Oxygen can be dissolved in blood without being bound to hemoglobin. The "oxygen saturation" measured by the fingertip oximeter is the amount of bound oxygen in the blood; obviously, once 100% of hemoglobin molecules are carrying their baggage of oxygen, there's no room for more. But there can be extra free oxygen just floating around in the blood if you have been breathing an oxygen-rich mixture, and as hemoglobin discharges its cargo more oxygen is present to bond to it. Therefore the decline in saturation percentage does not necessarily keep pace with change in altitude or in liters-per-minute delivered from the oxygen bottle. As Niederkohr explained, I would have seen more linear results if I had started from a minimum oxygen flow rate and worked upward.

Because my planned re-orientation of the intake manifold was going to encounter interference from the full-size starter motor that is currently on the engine, I got over my annoyance with Sky-Tec and returned my old small starter, together with a gift of $250, in exchange for a new small starter. I requested the same model, but somebody called me up from the factory and strongly suggested that I get the -5 rather than the -3 model, because that is what they recommend for the "larger" Continental engines. I think of my 360 cu. in. engine as one of the smaller Continentals, or at most as a medium-sized one, but I went for the -5 even though it weighs three pounds more than the -3. One advantage it has -- I think -- is that the -5 has a solenoid-operated electric clutch; the -3 has a centrifugal clutch. Now, the engine itself has a starter clutch consisting of a coil string that tightens around a shaft when torqued by the starter. In theory -- this must have been the theory that led the Sky-Tec people to design the original starter without a freewheeling mechanism -- the coil spring would completely disengage the engine from the starter, which did not want to rotate at all when it was not energized. But it turned out that the spring clutch would drag slightly, and tighten, and drag some more, until the whole assembly wore out and had to be replaced at a cost of over $800. For some reason I feel as if the solenoid clutch is more likely to resolve this problem completely than a centrifugal clutch is.

[June 24, 2011]

The oxygen system worked, but I can't make much sense of the pulse oximeter readings. I climbed to 12,500 feet and checked saturation; it was 83-86 (it tends to jump around a bit) and pulse was 106. (My resting pulse is usually around 60-65, but when oxygen is in short supply your pulse goes up.) I then put on the oxygen mask (which seems to be as good as new despite being more than 30 years old, but I haven't checked the built-in mic yet) and set 1.5 liters per minute on the flowmeter. Saturation percentage (hereinafter Sp) immediately went to 98 and pulse to 99. I kept reducing the flow rate with the following results (the first item is flow rate in liters per minute, the second Sp, the third pulse rate):

1.25: 98-99 / 90-92
1.00: 98 / 88-92
0.75: 96 / 90

So far so good. But this is where it gets weird. The flowmeter actually isn't marked below 1.0, but I thought I could extrapolate where 0.75 probably is. If I kept turning the knob the little ball became still. So maybe that's zero. But zero is about as far below 1.0 as 1.5 is above it, so maybe the thing is nonlinear at low flow rates, and that's probably why it isn't marked below 1.0.

With the knob screwed in all the way and the ball dead, I get 92-93 / 92-93. Then I disconnect the mask from the oxygen supply, and it goes to 90-91 / 91-94. So it looks as if oxygen remains bound to the blood for some time, because this is the same amount of oxygen as gave 83-86 / 106 before. Finally I connected the mask again and just cracked the valve, so that the ball gave a tiny movement: now I got 92-93 / 93.

I tentatively concluded that it's possible that the valve on the flowmeter doesn't close entirely. It would be interesting to know, if this is the case, what the flow rate is when the valve is ostensibly closed. Anyway, all this is of somewhat academic interest, since the value would be different higher up and in any case I would be adjusting the flow to get an Sp of 90 or so, which corresponds to about 9,000 feet without oxygen. I think I will repeat the whole experiment, but rather than start with 1.5 lpm and work down, I'll start with the valve closed and work upward; that will eliminate any lag effect, and will also make clear whether there is any difference between no oxygen at all and a closed valve on the flowmeter. I will also go to a higher altitude.

The flight, which was to Paso Robles, about 140 nm, took 1.1 hours up and an hour back, and used a total of 16.4 gallons of fuel.

Today I found that the battery water was down, just on the battery closer to the positive pole; so, as planned, I swapped the position of the batteries to see whether the excessive evaporation is due to the battery itself or to the battery tender that I use on the ground.

[June 22, 2011]

The oxygen bottle is now locked down and connected in a half-baked way to the regulator and outlets. I'm making a round trip of a few hundred miles tomorrow; I'm curious to see how my blood oxygen saturation responds to various rates of oxygen flow. Also whether the microphone in my oxygen mask still works after all these years. I probably last used that mask in 1982.

[June 14, 2011]

There is something about the arrival of summer that slows me to a crawl. The first heat is enervating; later I get used to it, and am probably less bothered by August and September than a lot of other people are. At any rate, I have accomplished almost nothing in the past three weeks, even though, after a few hot days, the weather had actually turned rather chilly and I was discouraged from going to the annual barbecue at Antique Aero in Paso Robles by rain, of all things. Not quite nothing, however. I have replaced the knob on the oxygen bottle valve with a lever and spring arrangement that will allow me to open it by pulling on a cord. It will require some sort of hook to hold the cord against the spring while the bottle is in use; when the cord is released, the spring closes the bottle. It seems to work satisfactorily on the bench, at least. I still have to figure out how I'm going to hold the ox bottle in place, but that shouldn't be difficult; there's a natural cradle for it under the rear seat footrest.

[May 25, 2011]

Further study of the problem of reversing the intake manifold has led me to think that it can be done after all by sawing up the existing manifold and ducting and welding it back together differently. The throttle body would end up right above the vacuum pump, which is okay, and the manifold would clear the oil filler neck on the left side of the engine. On the right side the old starter motor still creates a slight interference; I guess I will have to bend over and pay SkyTec for a new small starter that does not suffer from the same design fault as the one I currently have lying on the floor, where I wish I had left it when I first got it.

As for the matter of opening and closing the needle valve on the oxygen bottle by remote control, several suggestions have been offered, of which the most useful was to use an automotive speedometer cable with a small jackscrew. Jackscrews sound complicated, but are actually very easy to make with a bit of threaded rod or a sawn-off bolt. In the meantime my thinking had drifted to the minimalist solution of a piece of cord pulling the valve open and a spring pulling it shut. The current handle on the valve would of course be replaced with an arm a couple of inches long to provide some leverage and length of travel. As I mentioned a few days ago, the valve does not need to turn many times; somewhere between 45 and 90 degrees of rotation would be sufficient.

Since I have been thinking quite a bit about cooling issues, I got out my charts of delta p vs cooling air mass flow -- this is an item that manufacturers provide to OEMs -- and did a curve fit to the data. For what it's worth, the cooling air flow for my engine, in pounds per second, is 1.031 times the 0.541 power of delta p, the pressure drop across the engine expressed in inches of water. For cubic feet per second, replace 1.031 with 12.13 and divide by the density ratio. This is just part of what you need to know about cooling, unfortunately; other curves, which I have not yet modeled, relate delta p to power setting, ambient temperature, and cylinder head temperature. Ultimately, these calculations drive the size of inlets and outlets. I think, however, that inlet size, in particular, receives too much attention. People are very proud of having teeny-weeny round inlets. But you can't cram more air into an inlet than can find a way to get out. It is outlet size that controls the total mass flow, along with the impedance of the engine itself. Air finds its way around an oversized inlet, provided that it is well shaped, without a lot of trouble.

[May 20, 2011]

Since I am not one of those who believe that time ends tomorrow and am not a candidate for rapture in any case, I have been thinking about various things to do next. A couple of tasks remain unfinished: the oxygen system is hanging fire until I decide how I am going to open and shut the needle valve on the bottle, and I still need to install panel lights to complete the provisions for night flying. Actually, most people would consider night flying equipment to be incomplete until a landing light is added, so I guess I'm still far off. I don't fly at night any more, however, so none of this seems very urgent.

On the other hand, I do fly at high altitudes, and so the oxygen seems more useful. Yesterday Russ Hardwick and I discussed how to open and close the oxygen bottle by remote control. I was thinking about a torque tube; he suggested solenoids. A few minutes later he retracted the solenoid suggestion because it would shut the needle valve too violently and eventually damage it. I'm not sure that objection could not be dealt with by inserting a spring between the solenoid and the valve handle. He thought it would be best to use something that gave feedback, and proposed a hydraulic circuit; I made a counteroffer of a cable loop, but then raised him with a worm gear and sector driven by a small electric motor. It too would require some sort of spring or other cushion to avoid damaging the needle valve. Obviously, the options are impractically many. One of the desiderata is ease of removing the bottle; this is what inclined me to some sort of electrical solution. In any case I am indebted to Russ for pointing out that it is not necessary to turn the needle valve very far to provide the needed flow of oxygen. 45 degrees is plenty.

While I was mulling over all these choices, I also began thinking again about reversing the intake manifold in order to put the throttle body behind the engine, in the cool air side of the cowling, and to eliminate the transverse 2-inch tubes that currently impede air flowing out of the cooling air outlets. Today I uncowled the engine and studied the various interferences that I would encounter. I came to the conclusion that it would not be possible to simply make two saw cuts, flip something over, and come out with a workable reversed manifold. The oil filler neck gets in the way on one side and the starter motor mounting on the other. The oil filter, in its new position high on the firewall, is also a problem, and complicates running a pipe from the turbocharger to the throttle body. It appears that the best way to solve all of the problems will be to mount the throttle body wherever I want it to be, and then to bend and weld tubing as needed to connect it to the manifold and the turbocharger.

[May 9, 2011]

On Saturday I flew up to Pine Mountain Lake (Groveland), which is in the Sierra foothills on roughly the latitude of San Francisco, to present a little slide show about Melmoth 1 to the pilots' association there. My host overnight was Wayne Handley, a remarkable acrobatic pilot who is currently the president of the association. Wayne took me over to see Clay Lacy, whom I knew years ago at Van Nuys, having gotten my Learjet rating at his place. This turned out to be quite a stroll down memory lane. When we found him he was driving a 1955 Chevy Bel Air, turquoise and white, identical to my mother's car when I was an early teen. Clay's has 28,000 original miles, and looks it. In his hangar -- everybody there seemed to have a hangar -- was a Linn Midget Mustang that had belonged to the father of Clay's lady friend. That was an airplane that had impressed me quite a bit when I first saw it in Jane's in 1962, but I had never seen one in real life. Powered by a 125-hp converted GPU, it was quite fast, but I don't know how it managed to land; its tailwheel is about two inches in diameter, and its reported landing speed was 80 mph. That works out to over 13,000 rpm. Span is 16 feet. Not a lot of room inside for folding and unfolding WAC charts, or even arms.

The next morning the clouds were almost on the deck; I filed IFR back down to LA, flew the ILS at Van Nuys and broke off under the overcast to go to Whiteman. The makeshift GPS/VOR tracking system worked nicely, slaving to the old Lowrance GPS, either VOR or the ILS, or holding heading, as needed. You can do a lot with a wing leveler and one of these things.

Performance for the trip continued to be 170 ktas at 8.5 gph, which implies an F of 2.35 rather than the 2.25 I calculated a while ago. Ravages of time.

Today I was buying some more hydraulic fluid -- I still leak quite a bit of it -- when the radio shop guy walked by. I asked him about the PTT switch problem, and he suggested that it might be low voltage failing to operate a relay in the radio -- old radios, like my Collins MicroLine ones, had relays in the PTT circuit. That makes perfect sense. Next time, he said, try raising the rpm a little.

[May 4, 2011]

I had lunch at Camarillo with Javier Arango to discuss his collection of World War One airplanes, about which I am doing an article for Air & Space magazine. On starting up, I found that the press-to-talk switch on the radio would not work. This has happened a couple of times before, always after startup, and always it has resolved itself spontaneously after some time passed. This time I had to call the tower by cell phone to get a takeoff clearance. That worked fine, but when I was departing downwind the controller asked me to squawk NORDO. I reached over to select 7600 and then I suddenly thought, "Wait, is that hijack?" I couldn't remember, and not wishing to trigger a security emergency I dug around in my flight bag for one of those everything-you-need-to-know books. It turned out that NORDO is 7600; hijack is 7500. Anyway, I landed NORDO at Whiteman, taxied back to the hangar, turned off the plane, then turned on the master again and clicked the press-to-talk switch. It worked.

I sent the ox regulator to C&L Aero and have been making tooling for some fiberglass parts, including a fitted funnel for draining the oil. We had a visitor for a few days and I was going to museums and stuff rather than working on the plane; so I haven't gotten much done..

[April 22, 2011]

Further inspection revealed that the problem is simply that the relief valve on the oxygen pressure regulator is missing; broken off, in fact. If I put my thumb over the hole, the oxygen flows normally to the mask. Stumbling aimlessly around the Web with search strings that I never seem able to recreate later, I found C&L Aero in Redding, in Northern California, who charge $90 to overhaul an Alar A2000 -- though they admit that there are no life-limited parts in it, and so overhauling normally means just taking it apart, putting it back together, and, I suppose, maybe hitting it with a fresh coat of black paint. A replacement relief valve -- the originals are no longer to be found -- is another $45. On Monday I'll go by Norton Sales in North Hollywood, world center of aerospace equipment unobtainable elsewhere, to see whether they can do any better, but failing that C&L seems like a pretty good deal.

Yesterday was my granddaughter's birthday. My daughter (her aunt) gave her two tutus. She turned two, so there has to be a tongue-twister in there somewhere.

[April 20, 2011]

After correcting yesterday's errors I connected my welding oxygen bottle to the regulator and the outlets. Concerned that the decades-old armored high-pressure hose might burst and whip around murderously, I put a big piece of carpet on top of it and a packed parachute on top of that. I then just cracked the valve on the bottle. It gave forth a hissing sound that did not immediately diminish, so I gather something is leaking. Most likely the regulator is frozen after all these years. I'll test this more systematically tomorrow; I had a two-year-old sleeping in the car and she woke up just as I was starting. I looked around online for who might overhaul the regulator if it needs overhauling; one company promised a price of "under $600" -- which I suppose means $599.99 before tax -- for almost any regulator. That certainly seems generous -- to themselves.

My bottle, by the way, is a 680-liter (24 cu ft) aluminum one. It ought in principle to be sufficient for 20 hours at 18,000 ft for one person, assuming the most efficient delivery rate, which I gather from this excellent report is around 0.5 liter/minute. Less optimistically, ten hours or so. The report says that the valve on the bottle should not be opened until the oxygen is to be used; otherwise the bottle will leak down through a constant-flow regulator. So much for my idea of opening the bottle valve during the preflight.

[April 19, 2011]

A couple of people had suggestions about why the oxygen fittings are steel. One was fire resistance. That makes sense, but ought to apply to fuel as well as oxygen, and fuel lines are aluminum. Another suggestion was dissimilar metals corrosion, but since the body of the regulator is aluminum, not steel, that would not seem to be an issue. Oxygen is stored in aluminum, steel or composite bottles, and the valves on the bottles are generally either brass or steel. At any rate, there are just a few fittings, so I guess I'll stick with the steel. I installed the two outlets in the floor today, but I didn't get them quite right, and I'll have to redo the installation tomorrow. I also want to hook the whole system together outside the airplane to make sure it working before I install it. Baby steps.

[April 14, 2011]

Further study of the oxygen installation today. My regulator, an Alar A2000, was last overhauled in 1979. I'll try it and see how it performs. I rethought the question of whether or not to have a gauge, and decided that it would not be much trouble to install one alongside the two oxygen outlets. As for turning the bottle on and off, I think maybe I can make the valve accessible through a small hole in the back seat footrest. I'm curious why all the fittings associated with the regulator are steel; for small-diameter tubing, aluminum fittings would be amply strong. Rummaging through my junk collection I found that I have a lifetime supply of nasal cannulas; what hospital I robbed to get them, I can't recall. I need to read up on cannulas vs masks. I don't understand how flowing oxygen out of the cannula continuously, whether you're inhaling or exhaling, can be very efficient. Perhaps the flow is retarded by exhalation. I located a second ignition harness, which I assume must belong to the Slick mags. Still haven't found out the cost of the pressurization kit for the Bendixes, if in fact it even exists.

[April 13, 2011]

I have been closing in on installing the long-delayed oxygen system. It's pretty simple: a tank, a constant-flow regulator, two outlets, and a filling port in the sill of the baggage door. I am not currently planning to have a pressure gauge that is visible to the pilot; the idea would be to check the pressure gauge on the bottle before takeoff or know the pressure from a previous flight, and to know how much time a given pressure represents. So far I have just been figuring out how to arrange the various components so that they require a minimum of modification.

In addition to the oxygen system itself, I have to deal with the magneto pressurization question. Mags need to be pressurized to prevent cross-sparking at high altitude. Melmoth 2 started life with pressurized Slick mags, but after one of them failed in 2003 (a bad coil) I replaced them with the factory-supplied Bendixes that I had put into storage back when I first turbocharged Melmoth 1. Since then I have seldom flown above 15,500 feet. I recently learned that a pressurization kit is available for the Bendixes, which are generally thought to be of superior quality; I'm undecided about whether to invest in pressurizing the Bendixes or to just return to the Slicks, having replaced the bad coil a number of years ago.

[April 3, 2011]

I had a request from a French blogger, Xavier Cotton, for some observations about Melmoth's flying qualities. Cotton, who is a private pilot and an air traffic controller and obviously passioné des avions (crazy about airplanes), has a very nice site featuring pictures and descriptions of lots of interesting planes. If you don't understand French Google will provide a surprisingly readable translation, and the pictures are worth a visit.

When I began writing something for Cotton I realized, first, that I have never given much of a description of Melmoth 2's flying qualities here, and second, that it is difficult for me to do so, in part because I take them for granted and in part because they are -- I believe -- not particularly unusual. Nevertheless, here goes -- though this is less about qualities than procedures.

Taxiing is conventional, using nosewheel steering; if the CG is far aft, however, the nose strut extends fully, nosewheel steering disappears, and I am reduced to steering with brakes. This is very easy, fortunately.

I usually use 34/2,800 for takeoff, but I have up to 41 inches available. (The engine is rated at 200 hp at at 41/2,575; it probably puts out 230 hp or so at 41/2,800.) Acceleration is rapid (about .25 G) and I rotate at around 70 kias. I retract the gear, climb initially at 85 kias, and reduce power to 30/2500. After flap retraction, which takes a while because the flap has such a long way to go, the speed automatically settles at 95 kias. I am at 1000 agl by the time I turn from crosswind to downwind; I normally use the downwind departure at Whiteman because of Burbank Class C.

Once cleaned up, I lean the mixture to 50 degrees lean of peak and trim for a cruise-climb at about 110 kias and 8.6 gph (this does not make much sense; I should climb at a higher power setting, but still lean of peak). Rate of climb at this setting is 500 fpm when I'm alone in the airplane. I set the cowl flaps as required to hold the CHTs below 200 C. I tend to cruise high, climbing to 11,500 or 12,500 for any trip of an hour or more. A typical cruise power setting is 27/2,300, or about 55%, which gives 8.4-8.8 gph and 135-140 kias for a true speed around 170-175 ktas. On a standard day, the cowl flaps are fully closed. Handling is straightforward, with little adverse yaw and somewhat heavier roll forces than you would expect from such narrow ailerons; but the sidestick is very short. Roll-yaw coupling is satisfactory, and the airplane can be steered with rudder alone in smooth air without the ball getting very far out of center. Hands-off stability in smooth air is good; in turbulence, however, the high roll forces are fatiguing.

I usually cruise with the autopilot coupled to the GPS; it can also be coupled to either VOR. Ventilation is good, and I have never felt uncomfortably hot despite the bubble canopy. When roll trim is neutral, usually quite soon after takeoff, I turn on automatic fuel tank switching. The two fuel tanks switch automatically every seven minutes. In such an automated environment, the main challenge is to stay alert.

I usually begin my descent quite far out, reducing power to 20/1900 and descending at 500 to 800 fpm. Around three miles out, I turn off the fuel tank switcher, open the cowl flaps (in case it is necessary to go around) and deploy the airbrake (if it is not already out). At 100 kias or below I lower the landing gear and set 10 degrees of flap. The airbrake produces a nose-up trim change that more or less cancels the flap's nose-down one. Approach speed is around 75 kias, but I rely on the angle of attack indicator rather than the airspeed indicator for approach attitude guidance. On half-mile final I set full flap. I carry about 17-18 in Hg on final. I reduce power and begin to flare fairly high to bleed off speed, because the airplane likes to float. In ground effect I hold it off for as long as I can; the nose gets quite high, with the stall warning bleating during the final seconds before the wheels touch at around 50 kias. Stick forces are light during the flare and landing. When the mains touch I pull the stick all the way back to hold the nosewheel off -- with variable success. Once the nosewheel is down I brake firmly; the 3/8-inch thick brake pads provide good energy absorption and deceleration is quite strong. The airplane stops in a few hundred feet.

So that's about it; basically, except for its range of 3,000 miles, it seems like a normal airplane.

[March 23, 2011]

I climbed to 13,500 with the oximeter, which reports "saturation" -- the percentage of the potential oxygen capacity of blood that it is actually carrying -- and pulse rate. My resting pulse is usually in the 60s, but it was a steady 85 while flying. The saturation began at 99%, dropped to 98% at 7,000 feet, 94 at 10,000, and finally 86 at 13,500. There was some fluctuation, and saturation seemed to lag behind altitude by a minute or two, since the readings were different on the way down: 94% at 6,500, 96% on final approach, and 98% as I rolled up to my hangar.

At 13,500 I tried squaring some two-digit numbers in my head, and although I felt that I was doing it as rapidly as normally, I wrote down the answers and after landing found two out of three to be wrong. Furthermore, they were wrong in ways that were immediately obvious to me on the ground. For example, for 84^2 I wrote down 9,056. Now, it is self-evident that since 80^2 is 6,400 and 90^2 is 8,100, 84^2 cannot be 9,056. (It is in fact 7,056.) I'm not sure where the 9 came from; maybe I wrote it down incorrectly after solving correctly. But in any case, I missed the obvious mistake, and this probably had to do with my oxygen saturation being 86%. Whether this has any bearing at all on being able to cruise an airplane, I don't know. Cross-country flying on autopilot is mainly a matter of remaining awake. On the other hand, coping with an emergency is a hit-or-miss business; I have not always made good decisions in emergencies even at low altitude.

Here is a page, copied -- I hope this qualifies as "fair use" -- from a textbook found online, containing a chart of saturation against altitude (the latter being defined in terms of the oxygen partial pressure, which is 21% of the atmospheric pressure). I am a 67-year-old nonsmoker; it is not clear why the values given here are so different from the ones I recorded. Perhaps the oximeter is not reliable.

One noteworthy thing about this chart is the fact that the rate of loss of saturation with altitude increases rapidly above 12,000 feet or so.

On another topic, I checked the wingtip light flasher for radio noise. There was none.

[March 21, 2011]

For more than a week I've been helping my son help his wife prepare a yoga studio for its grand opening, which took place this last weekend. No time for the plane at all. But I finally got back out there today. The nav lights and flashers are now working, so that rather basic requirement is taken care of. I still need to rig up panel lights, however.

After writing about some hypoxia-related accidents for my June Aftermath column and then discovering that pulse oximeters have become very cheap. I bought one ($38). I intend to climb tomorrow -- between rainstorms -- to some goodly height and record my oxygen saturation. I have always believed that I can cruise for quite a while at 15,500 feet without supplemental oxygen and not experience any significant indications of hypoxia. To test myself, I would periodically square two-digit numbers mentally and assess how difficult I found the task and how long it took me. (This is a simple procedure, using the a^2 + 2ab (or -2ab) + b^2 template from high school algebra; it's just a matter of remembering the results of a couple of operations and adding them.) I am of course perfectly aware that a hypoxic person is not the best judge of his own mental capacities; but I am also aware that people react to altitude in quite different ways, and so I am curious to see an objective, numerical measure of my blood oxygen saturation and to compare it with some "normal" values, if I can find them. I have done a couple of pressure chamber rides, of course, but they are not really very informative, because their whole purpose is to hit you with a dramatic demonstration of oxygen deprivation; they never just take you to 14,000, say, and keep you there for two hours so that you can develop a more refined sense of what relatively mild hypoxia actually feels like.

I donate platelets at a local hospital every two weeks, and I asked one of the phlebotomists how, or whether, one's proneness to hypoxia would be affected by donating a pint of whole blood. She passed the question on to a doctor, who said that he didn't think so; but I doubt he had any special knowledge. I'll call FAA Aeromedical and see if I can find out something more than is contained in every magazine article about hypoxia written since the dawn of aviation.

[March 2, 2011]

Between wiring, bad weather and general distractions, I had not flown since returning from Santa Fe at the end of January; so this afternoon I cruised around the outskirts of the San Fernando Valley, down to Malibu, and back over the Sepulveda Pass and alongside Van Nuys. I found on approach to Whiteman that increasing the pitch trim tab travel from 20 to 25 degrees ANU did make it possible to trim hands-off to approach speed with takeoff, but not full, flap and the most forward CG position. Since I fly most of the approach with takeoff flap -- fully shifted aft to the trailing edge of the wing, but deflected only 10 degrees -- and go to the full 30-degree deflection only on a half mile final or so, this is adequate. When there are two or more people in the plane, or any baggage to speak of, I think I will be able to trim to approach speed, or quite close to it, even with full flap.

A correspondent, Frank Shoemaker, suggested checking the voltages of the two batteries after landing. I did so, and found the one closer to the negative pole to be at 12.9 to 13.0 volts and the other to be at 12.8 to 12.9. The next time I add water I will swap the positions of the batteries in order to see whether the difference is due to the batteries themselves or to their positions in the charging circuit. I will also check the voltages when the batteries have just been removed from their respective tenders to see whether they top off to different levels.

[February 25, 2011]

A couple of people suggested swapping the positions of the batteries to see whether the difference in water consumption moves with the battery. I will do that; but if the difference stays put, it will remain uncertain whether the reason is the physical position of the battery, its position in the electrical circuit, or the associated tender.

I posted another YouTube video, this one shot during a flight from Whiteman to Santa Paula. It's not very good, but, like Everest, it's there.

[February 24, 2011]

I've been stringing wires here and there, hooking up the nav lights, pitot heat, and flashers. I also happened to check the battery fluid level and found that it needed some water. But, as is always the case, one of the two batteries -- I use two 14-volt Yuasa motorcycle batteries in series to supply a 28-volt electrical system -- required much more water than the other. It is always the one closer to the negative pole. My first thought was that this had something to do with the battery tender, which keeps the batteries at top charge; but I use two of these "smart chargers," one for each battery, and so they should not behave differently. The battery that needs more water is farther from the exhaust pipe and other sources of radiated heat, and the batteries are in an insulated box anyway, so I don't suppose the difference has to do with temperature, unless from internal causes. Does anyone reading these bottle-messages know whether there is something about the order of the batteries in the circuit that would affect the evaporation of battery fluid, or whether this is simply a matter of two batteries having slightly different personalities?

For a long time I have been putting off installing the oxygen system that was always planned and that seems like a logical requirement for a turbocharged airplane. The problem with it is that it's added weight and would get used very seldom. Once in a while you can get extra speed high up, but it's costly, since although at home you can load your system with non-aviation oxygen at minimal cost, when you're away an oxygen charge is quite expensive -- probably more than an occasional 220-knot groundspeed is worth. My present inclination is to install the plumbing, which entails a comparatively small weight penalty, and leave the bottle behind unless I really think I'm going to use it. But of course what really happens is that you get lazy and just leave it in there.

[February 11, 2011]

I was afraid that upholstering the seat would change the feel of the cushions, and it did; the cover itself tends to compress things here and there, especially around the edges. The seat pan now felt too short, so I remade the metal brackets that hinge the back to the pan -- three times, in fact, since I kept making mistakes or changing my mind about what should be where -- and now it feels pretty comfortable. I won't know for certain until I make another 4-hour flight. I also removed, cleaned, and dry-lubed (with a graphite-moly disulphide spray that a reader recommended) the pins that hold the windows shut. I'm wondering, however, whether frozen grease was really what made them so stiff on my last trip, or whether it's actually the shrinking acrylic windows pulling the window frames out of shape.

Next project is to shim the gutters around the windows and hit them with a heat gun to temporarily soften the epoxy and, I hope, increase the clearance so that the windows are not so hard to open at low temperatures (this is a different problem from the difficulty with the locking pins).

[February 3, 2011]

I did the trim cable modification that I was thinking about a couple of weeks ago. It turned out to be more complicated than I anticipated -- what doesn't? -- and netted only a five-degree gain in aircraft nose-up trim tab deflection, from 20 degrees to 25. I picked up 10 degrees of additional travel in the nose-down direction, but that's pretty useless. I also put in a positive stop for the cable, so that the end of its range will no longer be signaled by the swaged cable end trying to wrap itself around a pulley. I have not yet flown to see whether the added tab travel has any effect on the minimum speed to which I can trim with a forward CG. What ultimately limited the tab's travel was not the cable or chain but clearances among the trim components, which are pretty tightly packed up in the T-tail intersection.

I also re-centered the out-of-whack flap valve and safetied the flap cable to the sector in the flap handle on the panel, so that it can't slip off the next time I fly into a deep freeze. Also, having flown many hours in my makeshift seat -- I can't even remember when I last adjusted the shape of the foam padding -- I took it to an upholstery shop in Highland Park to make it official. It's supposed to be done tomorrow. Who knows -- one of these days I may finish painting the instrument panel.

[January 30, 2011]

Most flights are entirely uneventful. A few are all too eventful.

I went to Santa Fe on Monday, January 24, to fly an airplane called the Sunbird Seeker at Albuquerque. After cruising at 13,500 where the OAT was -16 C, I descended into Santa Fe to find that when I selected flaps down the cable that connects the handle on the panel to the valve under the seat jumped its groove. Okay; I landed with no flap. The cable loop was surprisingly slack, and I concluded that the entire airplane had shrunk because of the cold. Since epoxy shrinks much more than steel, and for that matter the steel cable was within the warm cockpit, the effect had been to loosen the cable. I made a note to safety-wire the cable to the sector rather than rely on tension to hold it in place. Other temperature-related observations were that the window gutters interfere with the frames when cold and make the windows very hard to open, and that the window locking pins need to be thoroughly cleaned and dry-lubed. My well-intentioned greasing of them was fine for Southern California, but not such a great idea for a Rocky Mountain winter.

I felt some odd vibrations during that four-hour flight, and when I took off on Wednesday to return home I thought the engine did not feel right. I turned back to Santa Fe, where a mechanic named Kermit at Aero Services found my right mag to be 5 degrees more advanced than the left and my fine wire plugs, veterans of many happy hours in both Melmoth 1 and Melmoth 2, to be worn out. He rebuilt both mags (but did not replace any parts) and installed nine new massive-electrode plugs -- all they had in stock of the appropriate type -- along with the three least heinous of my old ones. I then started west, found the engine restored to smoothness, and got to Winslow as night was falling. I spent the night there.

In the morning the temperature was 14 degrees F. and the airplane was thoroughly cold-soaked. It took me a long time to get the engine to start; when it finally caught, I was using the flooded-engine technique -- mixture leaned, throttle wide open -- which often has the effect of letting the engine race briefly while you're getting the mixture forward and the throttle back. When I ran it up, I found the right mag seemingly completely dead and the left mag showing no drop -- as would be expected if the right mag were not supplying any spark. There was no mechanic at Winslow, but the FBO, Wiseman Aviation, also has a Flagstaff base, and they put me on the phone with the mechanic there. He said to disconnect the P lead from the right mag, since evidently something was grounding the mag. This was sensible advice, but it did not work out especially well.

I took off and found the engine still quite rough, so I went to Flagstaff, just 20 minutes away, and presented myself to the mechanic with whom I had spoken. His name was Rory Goforth -- a poetic name, I thought, for someone who sends airplanes roaring out into the world. I described the problem, including the fact that both mags had just been rebuilt. I should have kept my mouth shut. My explanation had the effect of convincing both him and me that the problem, whatever it was, could not be in the mags. In retrospect, this seems puzzling to me; after all, I had just found the right mag to be not working. But I had persuaded myself that this was due to the P lead, not the mag itself. Rory spent a couple of hours going over the usual suspects -- injectors, ignition harness, plugs -- without finding anything amiss. I took off again, flew ten miles, still didn't like the feel of it, and returned to Flagstaff.

At some point I suggested that I run up the engine and he listen to it. This wasn't especially brilliant -- it was the only thing left to do -- but it turned out to be what we should have done in the first place. As I turned off the left mag, the engine died on cue. But Rory heard something I hadn't heard -- a single pop; and he understood that it meant that the mag was not dead after all -- just malfunctioning badly. I tried the mag check again, this time letting the engine spool down for a longer time, and sure enough there was a series of pops. The right mag was firing on just one cylinder. This seemed mysterious until we looked -- at last! -- into the port at the nylon timing gear. I turned the prop. The gear did not turn. Eureka!

What apparently had happened was that the nylon gear, embrittled by age and cold, had shed a mess of teeth when the engine suddenly roared to life at Winslow. The replacement gear arrived the next morning and I returned to LA that afternoon. It was a smooth, windless and vibration-free flight.

A couple of days after returning, I was making circuits at Santa Paula for pictures to accompany a Technicalities column when I noticed that any time I operated the hydraulic pump the flaps moved upward slowly. What had happened was that the center-off positions of the panel handle and the valve had gotten misaligned when I tightened the flap cable loop at Santa Fe, so that when the handle was in the "off" position the valve was actually slightly open in the "down" direction. When tensioning the cable loop one has to adjust both legs, not just one. I had encountered that issue before; but since I have never compiled everything there is to know about Melmoth 2 into a service manual, I had forgotten about it over the years.

[January 20, 2011]

A minor irritant has been the inability to trim to approach speed at extreme forward CG; the best I seem to be able to do is about 1.4 Vs. Since I fly so much alone, and therefore at forward CG, it would be nice to have a little more trim authority. Currently the trim tabs deflect 20 degrees ANU (aircraft nose up) and 5 degrees AND. It happens that the AND authority is also just enough to cruise with extreme aft CG, and so I can't rob Peter to pay Paul. What currently limits the total tab travel is the distance between the trim wheel sprocket and a pair of pulleys behind the panel that turn the trim cables 90 degrees; the chain that the sprocket drives can't get closer than about two inches to the pulleys because of the length of the swaged cable fittings that link it to the cables. So the only way -- at least the only convenient way -- to get more tab travel is to replace those fittings with shorter ones.

On the suggestion of Russ Hardwick I found small aluminum cable splices at a hardware store; these can be swaged with a pair of pliers, and while their tensile strength is not that of a proper aircraft swage, it is certainly enough for a trim system. These look as if they will increase the chain travel by 40% and the total tab travel to 35 degrees. The more I think about how to perform the surgery, however, the more problems I recognize. For example, I seem not to have kept a record of the length of the chain in the T-tail, where the motion of the trim cables rotates a jackscrew; I will have to remove the rudder to find out. At any rate I guess I would have to remove the rudder to make sure that both chains are at the center of their travels at the same time. At least once the cable circuit is working, distributing trim authority between nose up and nose down is a simple matter of disconnecting the jackscrew nut from the tab and moving it forward or back.

Rather than replace the entire trim cable loop, I figured that I would just make new cable ends with the shorter end-loops and splice these onto the existing cables. One splice can be done with the little swaged fittings, but I thought the other might require some adjustment, and so after finding that my local bicycle shop didn't have anything suitable I made a little splice fitting. One cable inserts in a blind hole in one end and is locked in place with two set screws. The other enters on the same axis at the other end, but bends and emerges from the side of the fitting so that it can be held in tension with one hand while the other two set screw are being tightened. I use similar fittings on the cables going to the gear, flap and airbrake valves under the passenger seat, and they have worked pretty well. Here are the new, shorter cable ends and the splice fitting:

[January 15, 2011]

A visitor from France has been staying with us -- Vincent Legeay, who is in a Master's program in philosophy at the Sorbonne and is currently taking classes at U Mass and teaching French at Amherst College. We spend quite a bit of time discussing the prosody of Rimbaud, a topic in which I have an inexplicable interest. We flew out to Death Valley yesterday so that his experience of California could include something other than the many wonders of Los Angeles. On the return I got pilot reports of moderate and even severe turbulence over the mountains north of L.A., and so I stayed at 12,500 until we were over the San Fernando Valley and then descended somewhat rapidly. As it turned out, either this plan worked or there was no turbulence to start with, because we didn't run into much. It was glassy, warm and calm all over the desert. Vincent, dans l'avenir quand tu chercheras ton nom avec Google, tu te souviendras de ce vol.

Vincent Legeay in Melmoth 2, above the middle of nowhere.

[January 6, 2011]

I investigated the stiffness of the trimwheel and found that it was due to the grease in two bushings and jackscrew up in the T-tail joint having dried out. I guess I could use better-quality grease -- there are certainly lubricants that don't evaporate, or leave no residue when they do, and that don't stiffen up at low temperatures -- but instead I cleaned the offending parts with acetone and reassembled them dry. Metals of dissimilar hardness, like steel and aluminum, make naturally good bearings, at least at low rotational speed, even with no lubricant, so at least the two journal bearings should be all right. Both the male and the female components of the jackscrew are hardened, so I don't know how well they will work together; they may require a lubricant. At least the trim now works freely again, but I think I may still enlarge the trimwheel just to make it more sensitive.

[January 4, 2011]

From time to time I have mentioned that Melmoth 2's parasite drag coefficient is .022 (roughly) and I have commented that this is not especially low. Nevertheless, compared with a Mooney 201 (for example), whose parasite drag coefficient is said to be .017, M2 requires less fuel to achieve a given speed. To clarify this apparent contradiction, it must be said that parasite drag coefficient, although it seems like a nice, pure, technical way of expressing drag, is really almost meaningless, because it is based on wing area, which is used as a stand-in for the complete airplane. Obviously, this makes little sense; you could shrink the wings of an airplane and its drag coefficient would go up even though its drag would have come down. M2's wing area (105.4 square feet) is much smaller than a Mooney's (175). If M2 and a Mooney had the same drag, the Mooney's parasite drag coefficient would be .013, which would be fantastically low. (On the other hand, if Melmoth 2 had more wing area, it would also have more drag.) Some aerodynamicists prefer to cite a wetted area drag coefficient, which is based on the total surface area of the aircraft and therefore is theoretically more reflective of its size than wing area alone is; but actually from the point of view of the human occupants it would make more sense to base a drag coefficient on cabin volume or useful load or number of seats or some other ingredient or combination that might reflect the utility and perhaps even the comfort of the airplane. Equivalent flat plate area, or "drag area," which is a way of expressing actual drag, is closer to reality than parasite drag coefficient is; M2's is 2.3 square feet, the Mooney 201's is (according to at least one website) either 2.8 or 2.97, depending which numbers you use.

Fuel flow is not a good basis for comparison either. The aforementioned website gives a cruising speed of 160 knots for a Mooney 201 at 10.5 gallons an hour, presumably at around 8,000 feet. M2 uses 8.2 gph at that speed. But mixture setting could account for at least part of that difference. Besides, all these numbers are highly uncertain; different airplanes are tested by different people under different circumstances and for different purposes, and there is little consistency in the results. When the data from many years of CAFE races were reduced to equivalent-flat-plate form, it was striking how much variation in drag area there was within a given type and model, even though the airplanes were all exactly the same size.

A reader commented, with regard to my previous posting, that GPS is unlikely to be accurate to one centimeter. This is true. When I said that the Appareo stores lat-long data with a precision of one centimeter, I intended to distinguish between precision, which is simply the number of decimal places presented, and accuracy, which is fidelity to reality. For the purpose of measuring groundspeed, an accuracy of one foot, or about 30 cm, is enough, and it doesn't have to be absolute accuracy, just consistency from one moment to the next. In other words, it doesn't matter if the GPS has the lat-long of the airport wrong, provided that the error remains more or less constant over time. If the error were large and it fluctuated wildly, one would expect the speed trace calculated from successive lat-long positions to be jagged or bumpy. It isn't, and so I feel pretty confident that the speed measurements are as good as they need to be, given the underlying fallacy of using groundspeed as a surrogate for airspeed. The real question is, how precise, or accurate, is a limp windsock?

[January 2, 2011]

Last night, curious about whether the groundspeed data from the Appareo were being massaged in any way, I dumped the file to Excel and added a second groundspeed based on the variation, at 1/4-second intervals, of latitude and longitude, which the program stores with a precision of about one centimeter. I was initially disappointed to find that these instantaneous groundspeeds did not match the reported ones very well. Here is a plot of the two; blue is the Appareo output, red the values calculated in Excel from the raw lat-long data. (The four vertical red segments are spurious outliers.)

It's noteworthy that the lines coincide closely when speed varies in the same direction for a long time; but when speed is fluctuating somewhat randomly (for instance on the downwind leg) they get pretty far out of sync with one another. The Appareo line is evidently being smoothed or averaged somehow. My first reaction was dismay, but on closer examination I found that the portions of the lines that are of interest to me -- the areas during flare and touchdown -- coincide within less than a knot. The instantaneous values tend to be slightly lower than the smoothed ones, meaning that touchdown speeds are a bit lower than I thought -- about 50 knots with full flap at 1,900 pounds.

Unfortunately, the disparity between the two lines is greatest on the one landing that I did without flap -- the second-to-last in the graph -- and so I am no closer to a baseline to which to compare the flaps-down performance than I was before. The actual touchdown speed was several knots below the recorded 75, but how many I don't know.

[December 31, 2010]

Surprisingly, after the rain ended on the 29th there was a period of calm before the winds picked up, and, as I happened to be at the airport, I flew a series of touch and go's hoping to establish the touchdown speeds with various amounts of flap. (Touchdown speed is slightly different from stalling speed, because of ground effect.) I got my data, but it turns out to be harder to make sense of than I expected. The problem is that all of my landings were very smooth (of course!), and so there is no indication of the moment where the wheels touch the ground. Altitude doesn't work, because there is essentially no change in height from before touching to after. Furthermore, the Appareo software uses some sort of smoothing algorithm on vertical speed, so the vertical speed reported on the graph is not an instantaneous one. I can dump the data into Excel and fiddle with different moving-average schemes to come up with a better sense of instantaneous vertical speed, but that doesn't solve the more basic problem of being unable to tell at precisely what moment the landing occurred. I'm going to try pitch angle, although there too there is a problem, because it can increase momentarily after touchdown as I hold the nosewheel off.

Here is the record of the flight; if my subscription had not lapsed, it would have Google Earth surface data rather than a green grid for the background:

I took off from Runway 12, but after my first landing the tower changed the Runway to 30; hence the teardrop on the right. Weight was around 1,900 pounds, for a wing loading of 18 pounds per square foot. Airbrake was used with all landings; it contributes some lift. A lift coefficient (for the complete airplane) of 2.15 would be required to maintain 50 kias at this weight. My approaches are not particularly consistent.

Here is a typical graph generated by the software that comes with the instrument. You have your pick of ten parameters to plot; in this case, altitude (brown) is shown along with groundspeed (green). Of course, groundspeed isn't airspeed, but the windsock was limp during most of these landings. A movable cursor selects data for a particular moment; in this case, it is the lowest point on a circuit, which you would think would represent the ground; but maybe not. The software allows you to reconstruct all the flight maneuvers and review them from inside or outside the airplane, Flight Simulator-fashion.

If I add ground elevation to the plot, I see this interesting pattern:

The descending lobes represent the glidepath, roundout, ground roll, and takeoff. The duration of the segments where the lines are parallel is about 15 seconds, the altitude gain is 15 feet, and the average speed about 47 knots; that's about 1,185 feet. The runway rises about 50 feet over its 4,000-foot length, so the numbers are reasonably consistent. The gap between the two lines is due to some combination of the height of the instrument above the ground (about 5 feet) and GPS error.

So, on the assumption that the touchdowns occurred slightly to the right of the point where the two lines become precisely parallel, I get the following values for touchdown groundspeed:

30 degrees (landing) flap: 55.3, 50.2, 50.7, 40.4

10 degrees (takeoff) flap: 60.5, 56.8, 57.9

No flap: 75.4

The last full-flap figure seems way too low, and the no flap figure seems way too high; the power-off flaps-up stalling speed measured by Mike Melvill in 2002, when the airplane was about 200 pounds lighter, was 68 knots. But the results, such as they are, do suggest that my impression that the flaps took 15 knots off the landing speed is correct and not an artifact of pitot-static error.

I still need to see whether the reported airspeeds are instantaneous or, like the vertical speeds, moving averages.

Happy new year to all readers, wherever you are.

[December 28, 2010]

Yesterday I picked up Javier Arango's Appareo flight data collector, hoping to do a series of touch-and-go's to compare touchdown speeds with zero, takeoff and full flap. It was a perfect day for testing, with almost no wind. Unfortunately, when I started to record a flashing light told me that there was "no memory." I concluded that the flash card must be full, and so just went up and flew around for half an hour, cruising lazily around at 1,000 or so agl at 120 knots and 6 gallons an hour. On taking the whole rig home to charge it and empty the flash card I discovered that the problem was actually not that the flash card was full, but that it was not even in the device. It was in a card reader that came with it. Unfortunately, a cold front went through last night, and there are supposed to be advisory-level winds in the San Fernando Valley today, so I won't be able to conduct the test for a while.

It finally dawned on me that a solution to the stiffness of the pitch trim wheel -- a minor irritation that I have not previously mentioned here -- would be to use a trim wheel of larger diameter. Duh. Really, I am an idiot. I was so focused on trying to understand why the trim was stiff in the first place that I failed to see that the ready answer -- as I should know, living in gang-tormented Echo Park -- is brute force.

[December 18, 2010]

I dug up and scanned some old pictures taken during the construction of Melmoth 2. They're in a new section called "Construction" that is reachable from the home page.

[December 16, 2010]

I have been wondering why the #1 cylinder (right rear) runs hotter than the others. I had the cowling off for an oil change (not a single drop of oil leaked from the inverted oil filter, by the way) and I realized that the two hoods that I installed to direct cooling air over the unfinned surfaces of the exhaust ports on the #1 and #6 cylinders, and that had been effective in lowering their CHTs, were operating under somewhat different conditions. Air entering the hood on the #6 cylinder (left front) reaches the hood before it reaches the exhaust pipe. Air arriving at the hood on #1, however, passes over the exhaust pipe just before it enters the hood.

One of the objections to updraft cooling that I frequently heard during the design phase was that cooling air would be pre-heated by the exhaust pipes on its way to the cylinders. I reasoned that, air being a fairly good insulator, only the air in the boundary layer of a pipe would pick up much heat, and this would be a small fraction of all the air passing through the cowling. I think this reasoning is generally correct; on the whole the engine tends to over-cool, not under-cool. But local flow conditions may violate the general principle, and I think that may be happening here. This what the hood looks like:

Some, if not all, of the air entering the hood (the sheet-metal thing with the curved lip) is probably coming right out of the boundary layer of the exhaust pipe. It seems obvious that I ought to reshape that hood so that the air enters it from a different angle; I need to give a little thought to what that angle would be. I've occasionally thought about putting some tufts in the cowling and observing them with my miniature TV camera, but I've never seen tuft tests inside a cowling, and it may be that the flow is so chaotic that no useful information can be obtained.

Yesterday I spent quite a while thinking about where to put the three switches and one dimmer that will control the nav lights, flashers, pitot heat and panel lights. This is the kind of decision that is easily made on a crowded panel when it takes ingenuity to find any space at all. In this case, I had an empty area of 6x8 inches in which I could arrange the switches any way I liked. The infinitude of choices paralyzed me entirely.

[December 4, 2010]

I rerouted the wires in the flap coves yet again, on both sides. This time I think I got it right. None of the wires appears to be in any danger, even after years of vibration and neglect, of being frayed by any moving part.

In the course of raising and lowering the flaps I found that I have not been allowing the hydraulic pump to run long enough after the flaps reach the retracted position to completely equalize hydraulic fluid volumes in the master-to-slave lines, and as a result, for reasons that I do not understand and very likely never will, the right flap, over time, extends less and less far. From time to time I would correct the symmetry by opening the bubble catchers on the right side, pulling the flap all the way down, and adding fluid. It never took much -- a couple of tablespoons at most. But the small increment seems to make quite a difference. Fortunately, the ailerons have had no trouble overcoming the worst flap asymmetry that has yet occurred. I suspect that this may mean that increasing the angular deflection from the takeoff position, nominally 10 degrees, to landing, nominally 30, may be adding more drag than lift. Although the flaps are obviously very effective, I do not have a good handle on landing speeds, other than occasional glances at the ASI. I need to borrow from Javier Arango the Appareo flight data recorder. By flying a series of touch-and-go's, maybe three each with flaps set at zero, 10 and 30, I should be able to get a handle on the actual effect of the flaps. I suppose I could do the same thing with the Lowrance GPS in the airplane, but I'm not sure what its update rate is. The Appareo's is 4 per second.

I had a nice flight to Camarillo for lunch with Russ Hardwick on Thursday last. At 4,000 feet we doing 140 ktas at 6.9 gph -- about 41% of power, or 82 brake horsepower. This would have dropped to 135 ktas or so if we had had another pair of passengers in the back.

[November 14, 2010]

Having talked so much about having to refinish the kitchen floor, I might as well display the results. Here is what it looked like when we started in June:

The black vinyl tiles were in a dilapidated condition; under them was a layer of 3/8" particle board, and under that was a layer of felt or heavy paper of some sort, held down by thoroughly hardened tar. This had been a substrate for a linoleum floor that had since been removed. Under it was the damaged but salvageable 100-year-old subfloor of clear Doug fir. It took me a couple of months to remove the tar and paper with a paint scraper. Here is the final result:

It is discolored in places, scarred with nails, and patched where walls used to be or people cut out parts of it to gain access to the underside; but it looks nice now and feels good under one's bare feet.

On matters of greater international importance, I managed to feed the required additional wire from the nav light cove through the inaccessible void at the root of the upturned wingtip and out through a tiny hole into the aileron cove. I am now stringing it down to the fuselage, using a different routing than I used on the left side. I am happier with this one, and I'm going to go back to the left side and reroute the wires there.

[November 2, 2010]

I've barely gotten to the airport lately, but I put in a couple of hours today stringing wires from the left wing toward the fuselage. The wingtip has roll trim, nav light, a white halogen flasher and pitot heat, and the outboard fuel sender joins the parade at BL135. I did a very poor job of anticipating the need for a conduit for all these wires. I assumed there would be plenty of room along the rear spar, but it turns out that there are a few spots where it gets tight. I'm still not even sure I've done the smartest job of routing the bundle; I'm thinking maybe I should undo everything I did today and start over. I'll sleep on it.

[October 25, 2010]

Flew to Camarillo for lunch on Saturday with a couple of friends. One is a pilot (actually, both are, but the other flies only sailplanes) and he flew the outbound leg. After we landed, the tower asked us to expedite because of landing traffic, but did not use the "ground point eight leaving the runway" phrasing, so when we got to the taxiway we didn't know the ground frequency. My friend kept taxiing -- there were no other planes around -- as we tried 121.9 and then went back to the tower to inquire. Turns out it's 121.8. Anyway, as we taxied toward the restaurant he got the dreaded "After shutting down call this number" call. I had no idea what the problem was; I thought maybe we had gotten too close before calling the tower or had annoyed them by dropping down to 1,200 to stay below clouds when we had been instructed to maintain 1,500. But it turned out that the problem was that we had continued rolling while not in contact with ground control. He had several phone conversations with them with no result that I know of. He's an international airline captain, and left the next day for Europe. I assume the FAA just wanted to call the infraction to his attention. Anyway, live and learn; if you don't know the ground frequency, stop after leaving the runway and get it.

[October 13, 2010]

I have said, not altogether facetiously, that the advantage of oil leaks is that they can tell you things about airflow patterns. Here is an example. Predictably, air leaving the engine compartment around the cowl flap wants to emerge at a right angle to its steeply raked leading edge. On the inboard end, it is impeded by the wall of the chute; at the outboard end, on the other hand, where the gap is quite small, the flow does emerge at approximately a 40-degree angle to the flight direction. Shearing forces from the free stream tend to align the exit air with it; the oil streaks (the inner ones are quite faint) show both the process of alignment and the effect of the inboard wall on the flow direction.

[October 10, 2010]

Recently the right main landing gear strut developed a propensity for collapsing whenever I turned left off the runway after landing. By collapsing I mean that it compressed abnormally, so that the plane rolled along in a drunken attitude, right wing low, and, in one instance, fuel actually dribbled out of the right tip vent. As I continued to taxi in this embarrassing posture, the strut would gradually resume its normal height. If I tested the strut pressure by bouncing the wings up and down, the plane settled in a level attitude. A mechanic whom I asked about this behavior diagnosed it as a low fluid level. This makes sense; as the fluid level declines (through slow leakage past the piston O-ring, I suppose) more and more air takes its place, and the spring rate of the strut changes, making it "softer". Indeed, I don't believe I had added fluid to the right strut in the past eight years; so I jacked up the airplane and refilled the strut. This is a simple operation, which involves a special strut-bleeding tank acquired, I believe, from Aircraft Spruce. The tank is simply a plastic reservoir with a quart of hydraulic fluid in it and a pickup tube that connects to the strut's air valve with a fitting that depresses the valve plunger, allowing air and fluid to flow freely in or out. You compress and extend the strut two or three times, until air ceases to bubble into the tank. You then compress the strut fully, disconnect the tube, and finally fill the strut with air, using a strut pump, until about three inches of piston shows when the weight of the plane is on the strut. It is, by the way, incredibly difficult to compress the strut when it is full of fluid; you are not only lifting the weight of the wheel and part of the strut, but also forcing fluid through a tiny orifice.

Unfortunately, through some combination of stupidity and inexperience I did not think to drain the old fluid first, and so I ended up with a mixture of old, dirty fluid and new fluid in both the strut and the tank. I'm not sure how much this matters; it's possible that the viscosity of the fluid declines with age, but I have yet to make a bad enough landing for it to matter. I suppose, however, that I should do it again, on both struts, this time discarding the old fluid. Annual inspection time rolls around in November. The only way to get all of the old fluid out of a strut, however, is to remove the strut from the airplane and turn it upside-down, a requirement that just about triples the annoyingness of the task.

[October 3, 2010]

The kitchen floor is finally finished, but it has unfortunately reinforced my reputation for being able to make tolerable house repairs.

Last week I began wiring the nav lights. My usual scheme is to use a single shielded wire for a circuit, carrying the return through the shield, and I had accordingly run two wires to the light cove, one for the nav light and one for the halogen flasher. But Paul Lipps, who designed the flasher circuit, informed me that a single coax could not be used for the flashers; I think the reason is that part of the time the positive current would be in the shield, and would create radio noise. So I had to add a third wire. I thought it would be tricky, and it was, but I got it done on the left wing. The right will be trickier still, I know. The tail lights, on the other hand, will be very simple.

I've decided to do the revised turbo inlet duct next, but I am still trying to find out how best to turn a stream of air 90 degrees in zero distance. This seems like a rather obvious problem that people must have faced countless times, but I can't figure out what the search terms are that will bring me enlightenment.

[September 21, 2010]

We were away for a couple of weeks on our annual late-summer retreat to Cape Cod and environs. Yesterday I got out to the airport for the first time since returning. I just needed to pick up some tools for the perennial kitchen-floor project, but it was moving to see the plane again. "You're looking pretty good," I said aloud -- somewhat embarrassing, since I do not normally speak to inanimate objects, though I suppose there is no reason one should not. Even people often have no idea what I'm talking about.

I am tossing around in my head various ideas about what to do next. Obviously I need to wire the lights, but that's a minor chore. The major candidates are:

1. Replace the banjo box at the turbocharger inlet. I have come to feel that the 2-inch duct from the air filter to the turbo is too restrictive; air going through it must accelerate to nearly 200 mph at high power settings. Engine breathing would be improved by a larger duct. There are space restrictions, but I could probably enlarge the duct by 50%.

2. Reduce the aileron hinge moments. I have always felt that the stick forces in roll are too high. There are various ways to reduce them, including certain trailing-edge modifications, a simple servo tab, or new ailerons with more aerodynamic balance and the hinge line farther aft. The high forces are due to the cusped shape of the airfoil; they could be reduced by straightening the contours and using a beveled trailing edge, as Mooney does, but that is an ugly solution. There are possible flutter issues with a servo tab. Aerodynamic balance requires much larger gaps between aileron and wing. I have delayed doing this for a long time because I find the decision so difficult to make.

3. Revise the intake manifold. The present arrangement of the intake manifold seems to me illogical, given the arrangement of things in my cowling, and it clutters up the outlet path for cooling air. I would like to turn the manifold around, putting the throttle body above and behind the accessory case. This would be a pretty major modification, however, and its benefits are uncertain.

But first, the kitchen floor.

[August 23, 2010]

Assembled the tip lights just to make sure they would fit. I still have to add some wiring, etc. The white bulb is a halogen that is on a flasher circuit with the other tip and a similar tail light. The whole arrangement is quite primitive compared with modern LED lighting, but it has the great advantage of being practically free, since I already had the nav light assemblies left over from Melmoth 1. No doubt LEDs are brighter, last longer, and draw less current, but whether any of that affects one's enjoyment of flying, I don't know. I doubt it.

[August 11, 2010]

What with the removal of a wisdom tooth, lots of writing to do, the kitchen floor (still scraping; I can do three square feet an hour) and an unusual amount of software support needing to be provided to some new customers, I haven't been to the airport much. I did, however, do a cold compression check. The engine has about 1,200 hours, and the compressions were 78,77,78,78,77,71. The mechanic who lent me a compression tester commented that the next time I check it, the 71 will have become a 77 and a 78 will have dropped to 74. In other words, compression checks are not exact science. In fact, he considered them less useful than a sensitive ear for judging the state of the engine.

I began to fit the nav lights into their coves and promptly found that the mounting of nav lights and halogen flashers that I had painstakingly arranged would not fit comfortably under the lenses. Starting over.

[July 31, 2010]

Got back from Oshkosh this morning after a 3.7-hour flight from Santa Fe, where I had stopped for the night. The return took 10.3 hours in all, 1.1 more than the trip eastward; part of the excess was due to less favorable winds and part to the longer southern routing and some deviating around cells while leaving OSH and during an IFR stretch between Gallup and Prescott. The difference between block speed (takeoff to landing) and en-route speed is always surprising. Although I saw 180 knots or better on the GPS during almost all of the eastward trip and true airspeed around 176 knots at 12,000 feet, the block speed was just 168 knots. Overall fuel burn was around 8.8 gph, for a cost of $0.237/mi. Average fuel price was $4.61/gal.

Despite its annoying habit of dispensing a fine mist over the windscreen, the engine used only about one quart of oil per 15 hours. The trip was glitch-free, except for the nuisance of not being able to shut off the back seat ventilator from the front. I finally realized that a simple solution to that problem would be to put a remote-controlled butterfly or flapper valve into the duct leading to the vent. My brain had been stumped for a long time by the puzzle of how to control the vent from the pilot's seat. The adjustable outlet was taken from a Camry and its controls do not lend themselves to remote actuation. A separate valve upstream, however, would be comparatively simple.

The current arrangement of padding on the pilot's seat seemed to be pretty successful, although I started to experience some discomfort after 7 or 8 hours in the air. Maybe I can finally replace its pillowcase with genuine faux leather. I did somewhat miss having armrests.

Lately a couple of people have told me, without apparent embarrassment, that Melmoth 2 is quite ugly. One called it something only its designer could love, while the other confined himself to merely admitting that he liked Melmoth 1 better. I attribute their lack of inhibition to a sense that the fact is so obvious that there is no point avoiding mention of it, although the same reasoning does not, I believe, apply to babies. Fortunately, my granddaughter is extraordinarily comely. On the other hand there was general surprise (and I'm sure some unexpressed disbelief) at Oshkosh about a four-seat plane's cruising at 170 knots on 8.2 gph. Glasairs and such small deer do the same speed on 6, so I'm sure it's not that difficult. In fact, Melmoth's parasite drag coefficient (0.022) is not even remarkably low. It must be that those of certified airplanes (with a few exceptions) are comparatively high, or that their pilots do not lean the mixture as aggressively as I do.

While at OSH I talked briefly with Johnny Doo, Senior VP for Engineering and Product Integrity at Continental. I asked his opinion on the question of whether temperatures indicated by a bayonet thermocouple would be different, for a given overall cylinder temperature, in an updraft-cooled engine than in a downdraft-cooled one. He said he did not think there should be a difference. This confirmed my and Mike Melvill's opinion that since the bayonet is close to the exhaust port and the exhaust port is the hottest part of the head, the recommended bayonet reading would be the same in either case.

[July 28, 2010]

At Oshkosh. I took off from Whiteman Monday morning, IFR to VFR on top, and flew through an 800-mile convective sigmet that turned out not to be too big of a deal except for some moderate chop over the Rockies approaching Denver. I landed after 5.4 hours at Sidney, Nebraska, having used 45 gallons. On to Prairie du Chien, WI -- I sometimes pick stops based on proximity of airstrip to town on the map, and the attractiveness of local contours or, in this case, bodies of water -- in three hours, 26.8 gallons. There was a motel right across the street from the airstrip; left early the next morning, short but beautiful glassy flight over misty fields, and got into OSH a little after 7:00. Lots to see here, some amazing, some crap.

[July 20, 2010]

Except for countersinking the screw holes and installing lock-nutplates inside, the nav light lenses are done. They fair in nicely, in spite of having been formed over the outside of the wingtip. It remains only to put something under them.

[July 15, 2010]

The nav light lenses came in the form of lumps in a flat sheet of ploycarbonate. They reminded me of those loaf-like mountains in Chinese travel posters. It turns out that this plastic is so tough that it can readily be cut with tin snips, and so it was quite easy to trim away the excess material. Here are a couple of lenses, together with the tool that was used to form them. The tool consists of the actual pieces of leading edge skin that were cut out for the nav lights.

At my request John Eggett had made me two pairs. One I trimmed to fit and then cut in half along their leading edges. I taped the halves in place -- yesterday top, today bottom -- and laid up a couple of plies of fiberglass on the inside to serve as supporting flanges. I hope to be able to hold the lenses in place with just two screws, one each at the upper and lower corners. Here the upper flange is done and the lower half-lens is in place for laminating.

I am not very good at making paint stick.

[July 10, 2010]

The guys at Pacific Continental were very understanding about my failing to buy the intake manifold for $1,400 after they had located it, cleaned it up and alodined it. They confirmed that the throttle body can be in any position; it is a remarkably simple device -- they happened to have one on the bench -- consisting of a lopsided disk that slides across a small hole, gradually occluding it; this little hole is the fuel passage. What I need to study now is how to support the throttle body and where it will fit behind the engine. There is also a question in my mind about how tight a bend I can make in the 2.25-inch duct that will go from the turbocharger to the throttle. The intake manifold itself uses 2-inch tubing and bends of 4-inch radius on the tube centerline.

I picked up the nav light lenses on Friday. They are made of a polycarbonate that can be cut with a bandsaw and evidently lacks the propensity for cracking that makes plexiglas such a delightful material to work with. The question now is whether they will pull down to the leading edge radius -- they were formed on male molds that exactly match the wings, and so they are oversized by the thickness of the material. They seem pretty flexible, and so I am optimistic.

I have scraped the tar paper from about 60 percent of the kitchen floor now. It has taken three weeks. My right triceps is in great shape.

[July 7, 2010]

The absurdly high readings on the #5 CHT turned out to be due to the bayonet having fallen out of the cylinder head and ended up with its tip resting on an exhaust pipe. That is my one new CHT bayonet, and it has a crummy metal stamping for a retainer, unlike the more massive cast retainers on the others. Crummy though it is, however, the retainer still works if it's twisted on properly. Visual inspection of the dead EGT probe didn't reveal anything. Yesterday I had my biennial pitot-static check, and the mechanic who did it remarked that EGT probes fail pretty regularly; still, it could be a loose connection, perhaps behind the panel.

Pacific Continental Motors, an overhauler at Whiteman, called to say that they had found an intake manifold. During the episode of the worn-out starter clutch I had talked with them about my idea of reversing my intake manifold in order to keep it from obstructing the way to the cooling air outlets. I'm amazed that they actually remembered and did something about it, but now I'm also worried that I'm indebted to them and they're going to want some huge sum for the manifold. What I really wanted was to modify a spare manifold in advance, and then give whoever lent it to me my old manifold in exchange when I take it off. All this is by way of not grounding the airplane for too long. But I'm thinking now that maybe I could actually do most of the prep work before taking my engine apart. It's a fairly complicated job that involves not only the manifold but also the throttle body and throttle cable, air ducting between the turbo and the throttle, and the fuel plumbing between the throttle and the fuel pump and fuel distributor, but the simplification that occurred to me was to splice the manifold, where I intend to saw it apart, with rubber sleeves rather than by welding. This would be cheaper, and would also involve less risk of things not fitting together. Most of the other components could be prepared in advance without my actually having to dismantle the engine.

John Eggett, a neighbor of mine at the airport, formed nav light lenses for me, and they're ready for pick up. I may get them on in time for the trip to Oshkosh. If not, no harm. I no longer fly at night anyway.

[June 29, 2010]

I flew the plane for about 40 minutes yesterday afternoon. The OAT at 7,500 feet was 75 F., or about 43 F above standard, and the oil temperature never dropped below about 88 C (190 F). This was a little disappointing, but I suppose one has to make some concessions to atmospheric conditions. I will obviously not have the nav lights working by the time I leave for OSH; but I hope I will at least have the #5 CHT and #3 EGT back in line (the former is indicating a cylinder temperature of 650 and the latter is indicating nothing at all; neither can be correct).

There is always a fine mist of oil in the middle of my windscreen after I've flown. I attribute it to many little seeps in the engine, which sat for 20 years, its seals slowly hardening, while I was building this airplane. Oil droplets are picked up by the updraft airflow and come out the upper-surface vents. Most are carried to one side or the other without striking the windscreen, but those that arrive at the stagnation zone in the middle remain. Yesterday there was more oil than usual. I attribute it to my not having flown the plane for almost seven weeks, and more than the usual amount of drips having collected on the underside of the engine. But I will have to keep an eye on it.

Mac McClellan tells me that the FCC's crazy ban on 121.5 ELTs is being held in abeyance for the time being. That's a relief. I really needed to pay $1,500 for a new ELT.

[June 28, 2010]

No sooner did Nancy and I get home than I began work on removing our kitchen floor, which consists, or consisted, of black vinyl tiles decomposing upon a stratum of cratered particle board. The particle board came up easily, especially because Lily did most of the crowbar-wielding, commenting, no doubt with her just-ended years of academic labor in mind, that it was pleasant to do work that produced visible results. Underneath it is 100-year-old fir tongue-and-groove flooring, which, with some repair, will, I hope, take a finish and produce a nice rustic effect. First, however, the tar paper on it has to be removed, and this has turned out to be a major challenge. It is heavy paper, and has been stuck to the wood, and pressed down by generations of feet, for so long that the two have practically become one. It takes all my strength to scrape up some sections of it -- others lift more easily, having been less well secured to begin with. Irons, hair dryers and even floorers' heat guns have limited effect. I will soon be reduced to hiring a helper of fewer years and more muscles. All this is by way of saying that I have not been to the airport. Instead I have been stroking my aeronautical fur with mental images of reversed intake manifolds and revised air intakes. Four weeks til I leave for Oshkosh. I intend to fly this afternoon, to remind myself where the buttons are.

[June 8, 2010]

Nancy and I flew (commercially) to Providence on May 24 to watch our daughter graduate from Brown, and we are now on Cape Cod helping a friend clean up her summer house, which had some modifications done by workers apparently unacquainted with the concept of dust covers. We won't be back in LA before June 15.

I'm planning to go to Oshkosh this year. I'd like to get the EGTs and CHTs all working properly before that trip, but otherwise will not undertake anything very ambitious between now and the end of July. I am thinking about sleeping in the plane on that trip, or at least at Oshkosh, since I haven't made any reservations; it would realize a childish fantasy of footloose-and-fancy-free airborne wandering that I had when I designed the plane, but have never actually tried.

[May 14, 2010]

I finally added the bellmouth to the oil cooler duct inlet. It's unlikely to have a major effect on oil temperature, which has already dropped by 45 deg. F, but it just seemed like the right thing to do.

Readers who have followed this slowly unfolding saga will recall that the point of the elaborate duct was to provide the oil cooler with a flow of air that is 1) unheated by passage over the exhaust pipe and 2) unthrottled by the cowl flaps. As is apparent from the graph which I posted on November 9 of last year, the pressure drop across the engine is strongly influenced by the cowl flap setting. The difference between the pressure in the high-pressure plenum and ambient is larger than shown on that graph; when the cowl flaps are closed, it is about 12 inches of water at 140 kias -- nearly the dynamic pressure. According to Stewart-Warner's data on my oil cooler, a pressure drop of 12 inches of water implies a flow rate of 90 pounds of air per minute, or about 19 cu ft/sec at sea level. At a forward speed of 170 ktas or 285 ft/sec, this corresponds to a steam tube with a diameter of 3.5 inches, which is, in fact, exactly the diameter of the duct inlet. Since the air in the plenum is essentially stationary, it must accelerate to 285 ft/sec as it enters the duct; hence the need for a bellmouth to prevent the flow from separating on the sharp edge of the duct. These numbers are highly theoretical, naturally; there are bound to be all sorts of losses in the system. It would be interesting, however, to put a pitot tube behind the outlet hood and see what the velocity there really is.

By the way, the gray wire terminating in a quick-disconnect on the horizontal baffle goes to the electric cowl flaps.

[May 6, 2010]

I made a mess of the engine instrumentation the other day. The #1 cylinder CHT is working now; but the #3 CHT is intermittent and the #3 EGT has stopped working altogether. Evidently I disturbed them, to put it mildly, while fixing #1, which, by the way, turns out to be hotter than the other cylinders. That was disappointing; I thought I had corrected the tendency of #1 and #6 to run hotter than the others.

I was at Paso Robles yesterday and on the way back stopped at San Luis Obispo to see whether Don Dominguez at San Luis Avionics could figure out why my glidepath needle was motionless. He did; there was a broken wire on the little motor that drives the needle. He re-soldered it and now it works. While he was bench-testing the instrument he observed that the nav flag seemed to be inop. I was embarrassed not to have noticed it. He tried to fix it, decided that the actuator motor was faulty, and we discussed finding a replacement. I then took off southbound, tuned in the Santa Ynez VOR, and the nav flag worked fine. I realized that the reason I hadn't noticed that it wasn't working was that it wasn't not working. Why it failed on the bench is a puzzle.

The airplane was parked at a peculiar angle outside San Luis Avionics, and the fuel in the left wing went out to the tip. The pressure in the left main strut was low, and I had a hard time getting the plane to sit level enough for the fuel to drain back inboard. That's a problem with my rather small (3.2 degree) dihedral angle. I have never filled the tanks to capacity (71 gallons on each side) and so I don't know how bad it can get.

I still haven't gotten around to making the bellmouth for the oil cooler duct inlet. I need a short piece of tubing 3.5 inches in diameter, and I'm only slowly getting over my annoyance at Industrial Metal having a $6 minimum cutting charge. It used to be 50 cents.

[April 30, 2010]

On the 28th I set out to bring the dead CHT indicator in the #1 cylinder back to life.

To begin with, I knew the bayonet probe -- these are the old AN probes that stick up into the cylinder head casting -- was good, because I had previously swapped it with another. And I knew the instrument was good, because I have six cylinders hooked up to a twin-engine gauge by way of a three-position selector switch, in such a way that the rear, middle, or front cylinders' CHTs can be displayed in pairs, and all the others worked. So the problem was somewhere in the wiring. The wiring consists of the pigtails that are part of the thermocouple assembly itself; a length, equal among all probes, of special thermocouple wire whose electrical resistance is little affected by temperature; a 12-pin Molex connector; a short length of ordinary wire (we are now in the cabin, where temperature variations are small), the selector switch, a trimming potentiometer, a four-pin connector, and, finally, short lengths of ordinary wire going to the instrument, which has its own internal trimmers operated by two screws on the face. The likely culprits, I thought, were a broken connection either to the selector switch or the trimpots, or inside one of the Molex connectors.

The selector switch and the trimpots are in a single assembly with a connector at each end, and are located behind the instrument panel. Since the panel swings out, it was a fairly simple matter to remove the whole assembly and inspect and bench-test it for continuity. I found no problems. The wiring between it and the instrument was also evidently okay, because it is common to all three positions of the selector switch. Each thermocouple is electrically conductive, and by testing the conductor pairs in the 12-pin connector coming from the engine I determined what was by then obvious: that continuity in the faulty circuit was interrupted somewhere between the thermocouple and the instrument side of the 12-pin connector. The fault must be either in the engine side of the 12-pin connector or at the other end, where the special wires are connected to the thermocouple pigtails.

Since the 12-pin connector is comparatively difficult to get at, I decided to check the other end first, and immediately discovered that the cause of the problem was quite simple: an improperly crimped connector had come off a wire, producing not just a bad connection but no connection at all. I repaired it -- soldering as well as crimping this time -- and dipped the thermocouple in boiling water: 100 deg. C. (Actually, since the airport is at 1,000 feet agl the boiling point of water is around 99.5, but the instrument is too small, and the parallax too large, for half-degree differences to be discernible.) It may seem odd that I did not check that connection first, since it was easier to get at than the others. The reason was that I had checked it a couple of years ago when that probe was intermittent, and had found a loose screw and tightened it. I therefore assumed that the fault must be elsewhere.

It was oddly exciting to see that CHT probe working again, and I longed to go flying with it; but there was no time, and hasn't been any since.

[April 27, 2010]

Fans of the TV series 24 will perhaps find the person in the passenger seat familiar:

It's Arlo, the supposedly nerdy but actually cool guy who spies on all of Manhattan with a bunch of aerial drones. His real name is John Boyd, and he has been a great friend of my son's since they were both three. His girlfriend Nicole Vicius, also an actor and possessed of an unusually perfect philtrum, is in back. We are returning from lunch on Catalina, which is discernible through the rear window as a vague bluish undulation. I hasten to add that Nicole was in front on the flight over there; we do not make a policy of Mafia seating. Personally, I like the view backward, in life as well as in literature, and would sit in back if it did not make flying the plane so awkward.

I had put a folded paper towel in the cove in the right wing where the flap actuator leaks, hoping to find where the leak is coming from. When I took it out after one flight it showed considerably more blue stain than pink; evidently there is a fuel seep out there, which I have not been aware of because in local flying I seldom bring the fuel up to that level. I think minor fuel seeps are just something I'm going to have to live with, as if I owned an SR-71; it is impossible to get inside the wing to fix them.

Ever curious about engine temperatures, I calibrated my CHT system again -- I last did it seven years ago -- using a can of water brought to a boil with one of those plug-in one-cup tea-water heaters. The right bank of probes needed adjusting; they were indicating about 15 C. low. The left were right on. In fact, I found the consistency surprising; apart from the one probe from which I get no reading -- I'm going to try to track that problem down today -- four of the others indicated 100 and the fifth 98.

[April 2, 2010]

I collected some performance points the other day; I do this from time to time to see whether I'm gradually getting dirtier. I was at a density altitude of 10,000 feet. At 31 inches and 2,500 rpm, with a fuel flow of 9.4 gph, the indicated airspeed was 153 knots. This corresponds to an equivalent flat plate area of 2.3 square feet. For those who, like me, are fond of numbers, here is what the performance analysis routine in Loftsman makes of it:

Some of the headings may be less clear than others. ThpReq is the required horsepower to move a drag of 202.4 pounds at 153 kias; but because the prop efficiency (.857) is less than 100%, the engine has to produce 129 hp to yield 110.6 hp worth of work. Par/Ind is the ratio of parasite to induced drag; the induced drag is a little less than a tenth of the total drag. SFC, or specific fuel consumption, is the weight of fuel, in pounds per hour, consumed per brake horsepower. SpRange, or specific range, is the speed divided by the fuel flow -- in other words, nautical miles per gallon. BhpAvl is the available brake horsepower, which is 200 up to the critical altitude of the turbocharger, whatever that may be; the available thrust at maximum power would be 313.8 pounds. The 111.4 pounds of excess thrust (313.8 - 202.4) would yield a rate of climb at this speed of 1006.9 fpm (too much precision -- the calculation is not nearly that exact) and an angle of climb of 3.19 degrees. With zero power and thrust, the sink rate, again at 153 kias, would be 1,819.1 fpm, and the glide angle 5.78 degrees. The L/D ratio at 153 kias is 9.88 (the best L/D ratio, at around 100 kias, is 15.2 or so). Q is the dynamic pressure of air at this speed: 79.29 pounds per square foot. The lift coefficient for the complete airplane is 0.24, and the total drag coefficient is .0243, of which 0.022 is parasite and .0023 is induced. e is the span efficiency; the value, which is calculated somehow or other, seems unusually low; but at this speed it doesn't have a big effect on performance anyway. UnitRN is the Reynolds number per foot in millions, so that, for instance, for the wing's mean aerodynamic chord of about 3.2 feet the Reynolds number is around 4.7 million.

[April 1, 2010]

A promised rainstorm failed to materialize - the weatherman's blog called it an "April Fool's storm" - and instead it was a beautiful day with unusually clear air, puffy white clouds and mild winds. I had made a hood for the oil cooler air outlet, using the mold from the flap track fairings, in order to tame the chaotic flow that can be seen in the tuft photo from February 25. I had taped it in place temporarily and tufted its environment.

Today I made a short flight to test it. It looked pretty good, and so I glued it in. The tuft photo is a little hard to interpret because you can't get a good angle on the cowling from inside the cabin, but I could see that the tufts around the hood were steady and pointed in the right direction, and those in the row a foot behind it seemed undisturbed.

The whole setup is a violation of my general principle that inlets and outlets should be as few as possible, but it seems to have no ill effect on performance, so I guess either I got lucky or my general principle is not a sound one. Whether the hood has an ill effect on the rate of flow through the duct, and therefore on the oil temperature, I don't yet know.

[March 28, 2010]

Except for the bellmouth at the entry point, the oil cooler duct is now complete:

The baffling around the top of the duct is intended to prevent air on the downstream side of the engine from leaking into the duct. When the cowl flaps are closed, the pressure difference between the top (low pressure) side of the engine and the outside world can be much larger than the difference between the underside of the engine -- the high pressure plenum -- and the top.

[March 21, 2010]

Nancy and I went to the east coast for a week, where our daughter Lily was playing Masha in a Brown production of Three Sisters. She was terrific, by the way; I say this with complete objectivity, being notoriously inclined to overcompensate for parental bias. In the meantime our son Nick and his wife Samantha and their baby girl James were in LA, and now that we are back home I have been grandfatherly and have not been going to the airport; so nothing has happened to the airplane in the past couple of weeks. When I get back to it, later this week, I need first of all to get the baffling and fairing of the oil cooler air outlet worked out, and then to make a suitable bellmouth for the other end of the duct. Paul Lipps, who has been making a flasher controller for me, says it's almost ready, and so I guess the next task will be forming the wingtip light lenses and getting the nav and panel lights working.

I got a replacement glideslope receiver, but although the glideslope needle swings out of the way the needle doesn't move; so I guess the problem was not in the receiver after all.

[March 5, 2010]

Flew to Catalina today for lunch. Oil temperature is no longer an issue, but I have not yet made a fairing around the oil cooling air outlet and so I have not done any speed checks to find out whether this new modification has increased drag to a measurable extent. I did notice that one of my temporary duct tape baffle seals had prolapsed into the outlet. What I found most interesting today however was the impression that after landing the engine idled more smoothly at low rpm than it used to, and after shutting down I was able to turn the propeller with no more effort than at any other time. Before I changed the starter, the engine was very hard to turn over immediately after being shut down. Can it really be that the lightweight starter was exerting that much resistance?

[February 25, 2010]

Finally I have arrived at the end of a couple of tunnels. The matter of the starter has been resolved by putting the old 16-pound unit back on the engine. Now, with the help of batteries kept in tiptop shape by my battery tender, the engine cranks like mad. Sky-Tec, who made my lightweight starter, offers a special deal, a new 5-pound starter with internal clutch (to spare the engine clutch) for $250 and your old starter. Oddly enough, they did not offer to pay the $815 bill for the overhaul of my starter adapter, which their original idiotically designed starter had ruined. Eleven pounds is a lot, but I'm not sure it's worth $1,600. Maybe to the Pentagon.

On another front, I removed the duct extension that I had added to pick up oil cooler air from just behind the prop, and found that the oil runs just as cool without it. The key to a 20-25 deg. C reduction in oil temperature was, first, to pick up the oil cooling air before it had a chance to be heated by the exhaust pipes, and, second, to provide an outlet for it that was not affected by the cowl flaps. Incidentally, removing the duct extension (see Dec. 13) also had the happy effect of bringing down the temperature of the left front cylinder to where it had been before; evidently the suction from the oil cooler duct was starving it.

A tuft test of the region around the outlet revealed horrible flow; the tufts were jumping around like a bunch of dervishes. Actually, I have never seen a dervish. But anyway, I need to provide turning vanes and perhaps some sort of hood to smooth that out, and also a bellmouth at the intake end.

Finally, I made the mistake, when changing batteries, of failing to note the fuel quantity from the totalizer. Lacking any means to visually confirm the fuel level, I have hitherto relied on tapping on the underside of the tank; the resonance of the skin changes when there is fuel on it, and I have a graph that relates the fuel quantity to the outboard end of the fuel pool. Needless to say, this is a very approximate method. It came to me today, however -- it's incredible how long it can take for such an obvious idea to dawn -- that I could measure the fuel surface quite precisely by attaching a vinyl hose to a sump drain and noting the fuel level in the open end of the hose; my design software calculates tank volume for any pitch and roll attitude and fuel surface height. It appeared that there was 8.2 gallons in the right wing and 5.2 in the left. Using the tapping method, I had guessed 10 and 5.

[February 18, 2010]

At last the mystery of the balky starter appears to have been resolved. It seems that the first generation of the lightweight "high-torque" starters like my Sky-Tec lacked a clutch to disconnect them from the engine. The starter clutch inside the engine is a hefty coil spring that tightens around a shaft under load. The tension of the starter, which is a geared permanent magnet motor and does not turn freely when it is not energized, keeps the spring from relaxing, and eventually it wears to the point that it is no longer able to grip the shaft. The typical first symptom is exactly what happened: the prop stops at a compression peak and the starter makes a whirring sound. I removed the starter drive assembly from the engine and took it to Pacific Continental Engines, an overhauler on the field, where the guy I talked with said that if I had a Sky-Tec starter of the type whose driving nubbin cannot be turned by hand, I should throw it in the trash. This was discouraging news, but at least I still have my old starter. I then ran into Claude Morgan, who occupies the hanger two south of mine and has a Swift with a Continental 360 like mine. He turned out to be quite familiar with the problem, and said that he had put the old "18-pound starter" -- mine weighs only 16 -- back on his engine to avoid ruining the starter clutch. I am going to call Sky-Tec, whose website now makes a great point of how their current starters have electromagnetic clutches that prevent exactly what happened to me, and see whether they have a trade-in program. I'm not optimistic.

Incidentally, I was told that another cause of failures of Continental starter clutches is synthetic oil, which is so slippery that the coil spring can't get a good grip on the shaft. Lycoming engines don't have this problem (or the other one), because their starters engage by means of a small gear that pops forward to mesh with a large one. The system, called a Bendix drive, is out in the open air, unlike Continental's, which is inside the engine and bathed in oil.

Speaking of oil, I found out today that I had been right about one thing, at least: the inverted oil filter. I unscrewed it, and not a drop of oil came out.

[February 17, 2010]

I swapped my old 1970's starter motor for the Sky-Tec. It displays the same reluctance to turn over, so whatever the problem is it is probably not the starter. On the advice of Paul Lipps I checked the voltage drop all along the starter circuit with the small starter. I found nothing out of the ordinary, but since the small starter keeps whirring even when the prop is not turning, I wonder how much load it is really experiencing. Evidently its electromagnetic clutch is not engaging, and so it is never experiencing any torque to speak of. Tomorrow I will repeat the voltage drop survey with the old starter; at least when it bogs down, it stops dead.

My glideslope quit working a while ago, and I pulled the receiver, an ancient Collins GLS-350, today. It was incredibly difficult to get out, even though the instrument panels swings aside. It is held in place by a sliding shoe that is moved by a single screw; but I had put the head of that screw as nearly out of reach as it could possibly be. I'm going to arrange a better mount for it, although after this I will probably never have to remove it again.

[February 12, 2010]

I took out the batteries and worked for a couple of hours on assembling the charging socket and plug. After wiring up the part that goes inside the cowling I realized that it was going to be exposed to radiant heat from the exhaust and I could not use the wire that came with the battery tenders. I'll rewire that part on Monday. I tried cranking the engine with the mags and fuel pump off. There was very little voltage drop -- from 27 to 24 volts or so -- but that was not surprising since it was apparent that the starter motor is whirring but the prop is barely turning. I think there must be something wrong with the starter motor clutch. Bad news, if true.

[February 10, 2010]

Having built a sort of chimney on the top, that is downstream, side of the oil cooler, I reluctantly cut a hole in cowling top and made a test flight. The OAT on the ground was 19 C. The oil temperature rose to about 90 C during a climb to 8,500 feet, but then dropped to 78 C, which is the vernatherm setting, in cruise (27/2200, 141 kias, 8.4 gph). It was unaffected by my closing the cowl flaps; this was the result I was hoping to achieve. I still need to fair the edges of the hole in the cowling, provide some vanes to extract a few grams of thrust from turning the flow aft, and improve the sealing of the chimney -- I am temporarily using duct tape as a baffle seal.

The batteries were a huge disappointment, however. The starter barely turned the engine over. Actually, since it cranked equally weakly when being boosted by a Jet Center start cart at San Luis Obispo two weeks ago, the problem may not be the batteries at all. I will clean all the connections tomorrow and try it again. I had resolved to carefully watch the voltmeter during cranking to see how much drop there was under load, but then I forgot to do it. Maybe I'll remember tomorrow. I hope the problem is not the starter motor itself; that would be either expensive (buy another one) or heavy (install the gigantic original starter from 1970-something).

[February 3, 2010]

I've learned one or two things about batteries in the last few days. A couple of the important ones are that you don't replenish low fluid in a lead-acid battery with battery acid -- heck, it seemed so natural! -- and that a battery that sits unused for long periods needs to be on a continuous low charge to prevent accumulation of lead sulfate on its plates. A reader of this every-lengthening account, Glenn Stone, acquainted me with the notion of a "battery tender," which is a sort of trickle charger with the brains to maintain a "float" voltage just high enough to prevent sulfation and low enough to avoid eroding the plates. I bought a couple of them at Walmart ($20 bucks each, brand name Schumacher, look pretty solid) and hooked them up to my batteries yesterday, and today a couple of nice green lights indicate that the batteries are fully charged. I temporarily disconnected the tenders and measured the voltage at 26.6. I don't know if that's what it should be, but it seems high enough; it is slightly above the natural potential of 12 lead-acid cells, which would be around 25.2 to 25.6, and I suppose that it would drop rather quickly. I am going to install a socket in the bottom of the cowling to allow easy connecting and disconnecting of the tenders. The reason I needed two of them, if it's not obvious, is that I have two 12-volt batteries connected in series. They do not necessarily discharge and charge exactly equally, and in any case while 12-volt battery tenders are easily acquired, 24-volt ones appear, not surprisingly, to be rarer and more expensive.

[January 31, 2010]

The engine barely started for the SBP trip; in fact I had to get a fellow to come over and put away my homemade start cart and lock the hangar for me. Pleasant flight to SBP, the mountains unusually snowy after the previous week's storms.

The following morning my host, Kurt Colvin, who teaches engineering at Cal Poly and owns a Husky, and I found my wings heavily encrusted with frost. That took a while to go away, and then, of course, the engine would scarcely turn over; cold is no friend to batteries. Kurt tried without success to hand-prop it, and finally a start cart had to come over from the Jet Center. The engine should have whirled like a top, but it still cranked only weakly; it did start, however. On getting home and inspecting the batteries I found them to be heavily sulfated. In the course of acquiring new ones -- I use two 20-a.h. Yuasa motorcycle batteries in series -- and reading up on how to charge them, I learned that I have not been doing my batteries a favor for all these years by replenishing them with battery acid rather than distilled water; that just accelerates the sulfation by increasing the concentration of sulfuric acid, which apparently evaporates more slowly than the water. It is also advisable, it seems, to keep them on a "float" charger -- a steady 50-100 mA -- during periods of disuse. It is humbling to discover that I am still ignorant of such elementary things.

[January 19, 2010]

While rummaging through photographs to use as part of a presentation I'm giving to an EAA chapter in San Luis Obispo this coming weekend, I came upon this shot of an early, and abortive, project of mine called Tern, which is briefly described in the portion of this website devoted to the earlier Melmoth.

The paths of glory lead but to the grave.

A couple of people have suggested punching a hole in the oil filter a few minutes before unscrewing it to ensure that all the oil in it drains out. I was assuming that since the filter is above the engine and the circuit is open to the air through the crankcase, that would not be necessary; but maybe it will. If so, I will have to do it with something other than the recommended centerpunch, since the firewall, which is made of a ceramic/carbon/nomex sandwich and is very light, is not intended to withstand hammer blows.

I have been working on a design for a four-seat single-engine jet, a project originated by Austin Meyer of X-Plane fame, who apparently wishes to put to the test the adage that the way to make a small fortune in aviation is to begin with a large one. Here is what my design looks like; the rainbow colors represent pressures on the airplane surface, the red end of the spectrum being low pressure and the blue end high:

[January 13, 2010]

In accordance with my policy of veering off from time to time into some irrelevant activity, I removed the oil filter from its position on the right side of the nosewheel well/engine mount and put it on the firewall. Viz:

The idea was mainly to make it easier to get at, but also to see whether putting it into an inverted position would make it easier to change the filter without having to take elaborate precautions to avoid spilling oil all over the place. An inverted filter drains into the engine when it is shut down, except for oil that is below the top of the screw-on spigot; that, however, is supposed to be retained by a rubber flap around the perimeter of the filter. So in theory you should be able to remove the filter without any oil escaping from it at all. We'll see. Inverted filters are used on some cars, for instance MG-Bs (not much of a recommendation) and some Ferraris (hardly more). They are suspect in MGs because of the delay in developing oil pressure on startup; but in the airplane that should not be a problem, because oil does not even flow to the filter until the vernatherm valve opens. Since that happens gradually, I think the air in the filter should enter the engine in a fine stream of bubbles without affecting the lubrication. I made one circuit today to check for leaks. Everything seemed normal. I had moved the thermocouple (see below) to the top plug on the right middle cylinder; there it registered about 50 deg F higher than on the bottom, which is expected. I also looked at the bubble catchers in the flap hydraulics; nice and dry, and no air to speak of inside.

Paul Lamar, who is a guru of the rotary-engine community, said in one of his communications the other day that every 90-degree fitting in the oil plumbing raises the oil temperature, and that removing one could bring the oil temperature down 10 to 20 degrees. I have four of them. I don't understand, however, how they can affect the oil temperature, since the lubrication system is positive-displacement. They may raise the oil pressure a little, but I don't understand why they would have a detectable effect on temperature.

[January 7, 2010]

I've made a couple of flights now with the spark plug thermocouple; it seems to match up pretty well with the description in the previous entry, but I'm still not persuaded that temperature readings from a bayonet thermocouple should really be interpreted as being incorrect when cooling is updraft. I discussed this yesterday with Mike Melvill, who has updraft cooling in his Long-EZ. He observed that the tip of the bayonet, which is quite long, is buried deep within the cylinder head, close to the cylinder wall, and it is hard to imagine that blowing cool air on the other end of it could have much effect on its reading. That is my impression as well. We also agreed about the heat load in the cylinders being concentrated on their undersides -- see the previous entry. If the bayonet thermocouple reads low, perhaps it simply means that the hottest part of the cylinder is cooling better -- which would be a good thing, not a bad one. I wish I could find some serious technical analysis of this topic, rather than hand-me-down guidance in online discussion groups.

The last leak that I fixed on the flaps has had a remarkable effect. It didn't seem to be that bad a leak, but since I fixed it I have not yet had to add hydraulic fluid anywhere, and the flaps have been staying in synch with one another and extending fully at each use. It's too early to declare victory, especially since I haven't looked under the seats lately, but I'm encouraged.

[December 29, 2009]

The holidays have been a time of complete inactivity on the airplane front. However, Dick Eklund, who handles plans sales and support for the Thorp T-18, has sent me a couple of spark plug termocouples and a calibrated CHT gauge. With its help I hope to get some idea of the relation between the CHT as indicated by the bayonet probes, which are on the lower and therefore colder sides of the cylinder heads, and the factory CHT recommendation, which assumes downdraft cooling. I came across one plausible-sounding discussion of this topic on a Cozy site; here it is, slightly amended and amplified by me:

Lycoming says that cylinder head temperatures should never exceed 500 deg.F (260 C), but for maximum service life, cylinder head temperatures should be maintained below 435 deg.F (224 C) during high performance cruise, and below 400 deg.F (204 C) during economy cruise. High performance cruise is 75% power and 150 deg.F on the rich side of peak EGT. Economy cruise is less than 75% power and leaned to just above roughness. These temperature limits assume downdraft cooling and temperatures measured at the bayonet location under the cylinder, which is the hottest side with downdraft cooling. For updraft cooling you need to correct for the temperature difference across the cylinder, so add 40 deg.F (22 C) to the reading in climb and up to 70 deg.F (39 C) when leaned in cruise. If you are measuring CHTs with thermocouples under the bottom plugs, the temperatures are approximately correct without correction. If you are measuring CHTs with thermocouples under the top plugs, subtract 40 deg.F (22 C) from your readings to make them comparable to bayonet readings on the hottest side of the cylinder. So if you are using bayonet sensors on the bottom of the cylinders, your indicated temperatures should range from 300 deg.F (150 C) to 350 deg.F (175 C). Continental's recommended temperature for a bayonet thermocouple with downdraft cooling is 370 F (188 C); this would roughly correspond to 150 C for updraft cooling.

If, as I hope, this information is correct, it would suggest that I have been running 20-30 C hotter in economy cruise than I think I have. Unfortunately, the weasel words "up to 70 deg.F" leave room for doubt, and it is not clear why there should be different corrections for climb and for cruise. The matter is complicated by the fact that the bottoms of the cylinders, which with downdraft cooling would experience the greatest heat stress because the exhaust outlets are there and are provided with very little finning, would presumably be better cooled by updraft flow, while the tops of the cylinders, which have lots of fins but less concentrated heat, might receive less cooling but also need less. One might suppose that the temperature difference between tops and bottoms would be smaller with updraft cooling; the thermocouple readings from the top and bottom of a cylinder should shed some light on that. In the meantime, I can easily bring the CHTs down by opening the cowl flaps a little; that also reduces the oil temperature by a few degrees.

[December 14, 2009]

Finally, a palpable result. OT initially sat at about 80 C, then crept slowly to 85. This was with cowl flap open, that is, a decent delta-p (pressure drop) across the cooler. When I closed the cowl flaps the temperature went up to 88. Unfortunately, since I violated a basic rule of experimentation by making two changes at once (extending the duct intake to guaranteed cool air, and lagging the exhaust pipe near the duct) I do not know to what I owe the improvement. But the sensitivity to delta-p inclines me to think that it would be a good idea to provide the oil cooling air with a separate exit. For some reason, the temperature probe did not work on this flight, and so I could not confirm the temperature of the air within the duct.

[December 13, 2009]

On Friday I extended the oil cooler intake duct to a position just within the nose air inlet with the idea of picking up air before the engine gets a chance to heat it. I tried this before, but with such a tortuous duct that I was not sure that temperature gains were not being erased by duct losses. Anyway, in the next day or two I'll fly with this setup. The temperature probe is inside the duct; its lead is taped to the surface of the duct. I lagged the portion of the exhaust manifold that passes close by the oil cooler on the chance that a significant amount of heat is being radiated into the duct walls from the pipe. Here's the present setup:

You wouldn't guess it from the picture, but the cross-sectional area of the mouth of the duct is about 25% greater than that of the SCAT hose.

[December 9, 2009]

Yesterday I flew with the temperature probe in the oil cooler inlet duct. The temperature there was 34 C, the same as I measured behind the engine in the high-pressure plenum. The OAT was 10, so a considerable amount of heating of the cooling air is taking place before it actually gets to do any cooling. This may have to do with the location of the main air inlet just behind the propeller and below the spinner. It obliges air to flow around the oil sump and through an obstacle course of exhaust pipes and whatnot before getting to the cylinders and oil cooler. I have toyed with the idea of replacing the medial inlet with two inlets placed low on the cowling and some distance away from the propeller, something like this, but less ugly (that this is a T-34C, and the temperature was 34 C, moves me to think, annuit coeptis):

Such an inlet might improve the cooling air flow path. Despite the preheating of the cooling air, however, the cylinder head temps on this flight were about 150 C with the cowl flaps completely closed. CHT is not a problem.

[December 3, 2009]

Sifting through some old slides of Melmoth 1, I came upon a picture of the instrument panel that I think may have been taken while en route from Key West to Cozumel in the summer of 1974. It is interesting to compare it with a picture of the panel of Melmoth 2, taken in June, 2007 en route from Paso Robles to Los Angeles. Many of the instruments are the same, so it's easy to compare their readings.

First, performance. M1 -- this was early in its career -- was indicating 144 knots at 6,500 feet at 21.5/2500, that is, 161 ktas at maybe 70% power and a surprisingly rich mixture. The fuel flow is probably around 9.5 gph. M2, cruising at 11.500 feet at 26/2200 and lean of peak EGT, is indicating 141 knots, for a true airspeed of 169 knots at 8.8 gph (that's the fuel flow/totalizer at the upper right corner). This confirms my general observation that M2 is slightly faster and more efficient, despite being a four-seater; the big difference is its wingspan, which is over 35 feet to M1's 23. M1's cylinder head temps are at or above 200 C; M2's are 160 and 190, the 190 being the right rear (#1) cylinder, surprisingly enough after I figured out why it was running hot. I now cruise at between 150 and 180 C; but M1's oil temperature is about 65 C, whereas M2's is 100. The big difference in power settings is due to M2's being turbocharged and M1's having been naturally aspirated at the time the picture was taken. The manifold pressure gauge, by the way, is the same in both photos. It is a twin-engine gauge, and at some point I had the needles painted red and blue. The blue needle (needle #1 in 1974) is static pressure; it serves as a backup altimeter if you read it backwards from 30. The red needle (#2) is the manifold pressure.

[December 2, 2009]

Finally back to the hangar after a couple of weeks of holiday cooking and hanging out with our son and his wife and now seven-month-old daughter. I took out the #1 bubble catcher, which was still leaking hydraulic fluid, chased the threads, and potted an AN fitting into it with JB Weld. That should work. I then made a flight to check oil temperature with the duct as it appears in the photo below -- no hose, no bellmouth, just a way of getting at air that has not been playing footsie with the exhaust pipes. The result was not too promising: still 100 degrees C, even though the OAT was 13. I'll put the temperature probe inside the duct next.

[November 14, 2009]

A morning both eventful and unsatisfactory. I got out to the airport at 6:20 a.m. and attached the duct to the oil cooler. I didn't want to cut an expensive piece of 3.5" SCAT until I knew exactly how much I'd need, so I crammed about 40 inches of the stuff into the cowling and tied it down with safety wire. The front end is about 10 inches behind the air inlet. I then took off to test the cooler. There ensued another one of those educational glitch-parades that make test flying so amusing. The cable connecting the flap handle to the flap valve jumped its track when I was putting the flap handle back into the neutral position after setting the flaps for takeoff, but I was unaware of it. When I went to retract the flaps, the flap handle jammed, with the result that the hydraulic pump ran continuously. I had to pull a breaker to stop it. But rather than retract, the flaps went to the landing position, because the valve was not following instructions from the handle. So I flew around the pattern at 80 knots, got the gear down by briefly resetting the breaker, and taxied back to the hangar. The problem was easily corrected, and I re-tensioned the cable so that it would not misbehave again, at least not immediately. I then went out to fly again. This time the left flap, which is always the troublesome one, did not extend symmetrically, so I left the flaps up and took off. Disappointingly, the oil temperature went up to about 90 C. This is better than it was, but it was a chilly morning, at least by LA standards, and it's hard to separate the effects of cooler ambient air from those of the duct. I had of course been hoping that the temperature would go to the factory-recommended 77 C and stay there. So now the question is whether the long, somewhat tortuous duct is impeding the flow, or the lack of large improvement is due to about ten other possibilities I can think of.

One observation I made that was of interest (to me, at least) was that the temperature behind the engine, on the "cold" side of the baffles, was around 40 C -- that is, quite a lot lower than the temperature at the inlet to the oil cooler. So the oil cooler seems to be getting a specially heated stream of air; this may help explain why the oil temperature is high, but the cylinder head temperatures aren't.

[November 13, 2009]

I got the oil cooler duct done just too late to add a bit of SCAT hose going to the air inlet and make a test flight. I hope to do it over the weekend. The duct is entirely flush-riveted, with the flush heads inside.

It will be interesting to see how this affects the oil temperature and also how the oil temperature is affected by the cowl flap position. I suppose that ideally the oil cooler would have its own air outlet, so that it experienced maximum delta-p at all times. On the other hand, you don't want to be putting more air through the cooler than it needs. The engine temperature is regulated by the vernatherm valve, which controls the flow of oil to the cooler. In principle you would like the vernatherm to be fully open when the oil temperature is at the recommended 170 deg. F; that would mean that the amount of oil cooling available is exactly the amount needed, and no extra air is being sent through the oil cooler. But I am getting ahead of myself. The first thing to find out is whether the duct brings the oil temperature down or not.

[November 10, 2009]

I am once again indebted to my alert Swedish correspondent, Jan Carlsson, who continues thinking after I stop, for pointing out that it is not impossible, as I said yesterday, that the static pressure in the plenum be greater than q. The source of the extra pressure would be the propeller. Duh.

[November 9, 2009]

On Sunday Hans Kandlbauer and I collected another batch of cowl pressure data. We had generally smooth air, which is needed because the water manometer is very sensitive to little jiggles. Nevertheless, some of the results were suspect; the pressure in the bottom plenum was a little higher than q at low speeds, which is impossible. For what it's worth, however, here is the variation of delta p, the pressure drop across the engine, at a range of cowl flap positions and airspeeds. There is some scatter in the data, especially at 100 knots.

The cowl flap position values are the size of the opening at the aft edge of the flap. Because of the deformation of the cowling under pressure and the placement of the limit microswitch, the flaps stop slightly short of fully closed. At 140 kias, zero is really 0.25; at 80 kias, it is more like 0.15. The line colors are indicated airspeed in knots. It is interesting to note that the last half-inch of travel, between the "climb" position (1.5) and the "ground cool-down" position (2), yields barely any gain. Otherwise, however, the variation of delta p with respect to outlet area is pretty linear. The outlet area at 1.5 is about 60 sq. in., which is approximately equal to the inlet area.

[November 5, 2009]

There's supposed to be a guy at the airport who has an oven with provisions for vacuum-forming plastic lenses. I go by his hangar every day, but he never seems to be there. In the meantime, I've gotten interested in the oil temperature question and am making a duct, as suggested by Jan Carlsson, to pick up cool air before it has had a chance to flow over the exhaust pipes. Every once in a while I treat myself to a little nostalgic metal work -- my first airplane was all-metal -- and I remember how much fun it is. Sheet aluminum is like a child: It doesn't want to do what you want it to do, so you have to trick it or compromise with it. (Some people beat on it, but I am of the nonviolent generation.) Here is the duct after a few hours of work:

That's a spare oil cooler -- I didn't have to take it off the engine. The entry to the wedge diffuser below the cooler is 10 square inches -- a wild guess -- and I just happened to have some 3.5-inch SCAT, which is the same size. The duct bends down 90 degrees and forward 30, while transitioning from a 3.5-inch circle to a 4 x 2.5-inch rectangle.

While measuring the temperature of the air entering the oil cooler last week, I took a few pictures of tufts on the rear window. There is some slight unsteadiness along the centerline at the extreme aft end of the canopy, but the view is probably worth it, since the rear seats face aft. Yes, the upholstery of the pilot's seat is still a pillowcase.

[October 30, 2009]

After my last posting I received an e-mail from Jan Carlsson of JC Propeller Design in Sweden, suggesting that the reason for my high oil temperature was that the exhaust pipes were preheating the air going into the oil cooler. I didn't believe that this could be the case, since the cylinder head temperatures are quite low, and they would be under the same influence. Today I measured the temperature at the entrance to the oil cooler, and found that I was wrong and he was right; the temperature was in the neighborhood of 60-65 C, or around 150 F. Small wonder the oil is hot. Jan suggests a duct from the air inlet to the oil cooler; another possibility would be a separate air inlet on the cowling side, which would make quite a crowd of inlets, since the induction air NACA scoop is there already. A third possibility would be an insulated plenum built into the bottom of the cowling, fed from the front inlet, supplying both the oil cooler and the induction and supplanting the NACA induction-air inlet. I'll think about this for a while. I also need to repeat the test, and measure the temperature of the air emerging from the cooler, to be sure that I am separating radiant from convective components properly.

The gadget with which I measured the temperature, by the way, I got at Radio Shack in November, 2003. It's intended for letting you know when the meat on your barbecue is ready, and consists of a probe, a transmitter, and a remote receiver that displays temperature. It cost about $25.

[October 28, 2009]

On Sunday Hans Kandlbauer and I collected cowl pressure data using a water manometer with two circuits, one comparing the high- and low-pressure plena (this is "delta-p", the pressure drop across the engine), the other low-pressure (as I thought) and static. The results looked pretty nonsensical until I realized that the low-pressure vs. static data were really high-pressure vs static. Then they made sense, but just to be sure I'm going to run the tests again. The confusion was due to the ambiguous labeling of some pressure hoses I had installed years ago; "low" could mean low pressure or low (that is, below the engine) plenum; obviously, in an updraft system the physically lower plenum has the higher air pressure.

The aim of all this data gathering is to understand why the oil temperature is higher than expected. It runs between 90 and 110 deg. C, depending on OAT (Southern California tends to be way above standard almost all year long) and cowl flap position. The factory recommendation is 170 F, or 77 C. The oil cooler is part of the engine, and the whole arrangement is the same as it was on Melmoth 1, except that the air flow is in the opposite direction and the length of the hoses going from the engine to the oil filter is greater (an extra three feet or so of 1/2 inch tubing). The filter is of concern because I have installed a diverter between the engine and the oil cooler; oil heading for the cooler gets sent through the filter first. The filter is a few inches away from an exhaust pipe, and I suppose that some radiant heating must be taking place, but certainly not enough to account for the observed temperature increment. The oil pressure runs about 45 psi in cruise, and since the oil pump is a positive-displacement device there is no reason to think that the impedance of the plumbing and the filter itself (which is a Bosch automotive model) is responsible. Just to make sure, I intend to short-circuit the diverter, bypassing the filter. I will also calibrate the oil temperature probe, though I have done this before and have no reason to suppose that its behavior has changed.

On Melmoth 1, the oil temperature maintained the factory Vernatherm setting of 170 F. One possible explanation for the difference now is that because the CHT probes are on the bottoms of the cylinder heads, they indicate cooler, for a given overall heat content in the cylinder head, than they would with downdraft cooling. That would imply that I should be aiming for CHTs lower than the recommended 370 F, which would mean a larger cowl flap opening, which would mean higher delta-p. It's evident that the minimum cowl flap opening of 18 square inches, which I normally use when cruising, results in a buildup of pressure above the engine and a consequent drop in delta-p; at 140 kias with the cowl flaps closed, we measured a delta-p of just four inches of water, which is less than a third of the total pressure. But even with the cowl flaps open and the CHTs abnormally low, the oil temperature never drops to 170 F.

[October 22, 2009]

Today I finally managed to record the tuft test of flow attachment on the stabilizer during the landing. CG was about as far forward as it gets, with full flap and no airbrake (the airbrake produces a nose-up pitching moment, and so it reduces the tail load). The video is short and somewhat difficult to interpret. It begins as the airplane crosses the airport boundary; the trimmed elevator angle is about -5 degrees. The approach speed is too high and so the flare goes on for some time; you can see the stabilizer hunting farther and farther upward, beginning about 9 seconds in. The landing itself is not detectable on the tape; but at 17 seconds the elevator suddenly deflects fully upward. At that point, the main wheels are already on the ground and I am holding the nosewheel off. When the elevator is fully deflected, the flow on it is separated; but there is practically no flow reversal while the plane is airborne.

[October 21, 2009]

Several people wrote to suggest that the low airspeed reading on landing might be due to a particularly steep pitch attitude -- that is, to pitot, not static error. But with full flap the pitch attitude on landing is actually quite flat, so I don't think that's it. This weekend I am planning to do some landings while someone in the right seat watches the GPS. I'm not certain this will tell me much, however, since the apparent position error is in the range of 3-5 knots, and uncertainty about the wind could be in that range as well. We'll see. I have also hooked up the little camera that I mounted on the tail a while ago; it is looking up at the horizontal tail, which I have tufted in order to see whether the elevator flow is separating during the landing flare. Another task in this little set of tests will be to record pressures in the cowling at various speeds and cowl flap settings, using a water manometer.

I have also made the male tool for the wingtip lenses, and yesterday I laid up a couple of plies of glass over it in order to make temporary covers for the holes in the leading edges where the lights will eventually be. These covers will also serve, later, as templates for trimming the plexiglas lenses. The actual mold for the lenses will be a plaster female, and I hope to draw the heated plexiglas into it with a slight vacuum.

[October 9, 2009]

I had some e-mail discussion this morning with John Roncz regarding the landing speed of 48 kias. We agreed that it is implausibly low, implying a CL for the complete airplane of more than 2.6. John said he would have expected something closer to 2.2-2.3, which would give a stalling speed of around 53 knots. So the question is, why is the indication so low? One explanation would be position error; but a position error of 5 knots would require a high, and unlikely, positive pressure at the static ports. I then ran a Cmarc analysis of the airplane, flaps down, in and out of ground effect. At an angle of attack of six degrees, the predicted CL for the complete airplane was 2.17; in ground effect, at the same angle of attack, it was 2.54. This difference pretty closely corresponds to the disparity between the expected and the observed stalling speeds, but this may be mere coincidence, since I am not sure that a wing should be expected to stall at exactly the same angle of attack in and out of ground effect. Since Cmarc predicts CL but not the stall itself, these analyses may or may not have much relevance to the question; but they do suggest that an airplane might possibly touch down at a speed somewhat lower than its stalling speed out of ground effect.

Incidentally, at Melmoth 2's wing loading of about 20 pounds per square foot and at landing CLs in the vicinity of 2.0, a change of 0.1 in the maximum lift coefficient produces a change of one knot in the stalling speed. The landing rollout is proportional to the square of the speed at touchdown, and so each added knot of landing speed represents a change of about four percent in the landing distance. If the braking distance is 500 feet with a touchdown speed of 50 knots, it will be 600 feet for 55 knots. The extra 100 feet would be covered in about 1.3 seconds during the flare. That is why speed control during the approach is so important for maximum performance landings -- more important, usually, than small differences in maximum lift coefficient.

[October 8, 2009]

Finally, I managed to shoot some tape of the flap with tufts.

A video of one circuit around the pattern at Whiteman is on YouTube. Unfortunately, in order to get as much of the flap as possible into the frame I was obliged to tilt the camera about 40 degrees. This test was flown at 2,200 pounds, with 100 pounds of ballast in the baggage compartment in order to be able to trim hands-off at approach speed, or anyway what the Safe Flight angle of attack device thinks is approach speed (about 73 knots with full flap; 1.3 Vs would be more like 65). All tufts are attached and steady during takeoff and climb. When the flap is retracted, a large area of unsteady or reversed flow appears near the trailing edge of the wing. I have discussed this earlier (3/17/09); it is probably due to the thickness of the laminar airfoil, which is 18% out to BL 48. The outboard set of tufts, which are at about BL 125, are in better shape; the thickness there is more like 15%. It is unlikely that a wing root fairing would have any effect on this separation; the tufts at the bottom of the frame are at BL 48, and the side of the fuselage is at BL 25. Accelerating to about 100 kias, which is five knots above the theoretical speed for best rate of climb, removes most of the unsteadiness.

The flow attachment with full flap is just about perfect right down to touchdown, except in the wake of the middle track. This is not especially surprising, since the maximum deflection is only 30 degrees with respect to the wing chord line; if it were 40 degrees, there might be more separation. Around the middle track, the flow is attached over the front portion of the airfoil, so it is generating some lift, but completely separated over the aft portion. The reason the disturbance seems to be located mainly on the inboard side of the track is that the rear spar has forward sweep, and the flap track is at a right angle to it. It is therefore angled outward with respect to the air stream.

Touchdown occurs, as I noted yesterday with condign skepticism, at an indicated 48 knots.

[October 7, 2009]

Yesterday I tufted the left wing and flap and set up a video camera to record some takeoffs and landings. I put 50 pounds of ballast into the baggage compartment in order to make it possible to trim to approach speed with full flap. Today I flew to Santa Paula, bought 40 gallons of fuel, and flew back, reaching back over my left shoulder to turn the camera on and off. Unfortunately, I couldn't see the monitor, and upon inspecting the tape at Whiteman I discovered that I had recorded, in all, approximately three seconds in cruise somewhere over the Santa Clarita valley. I'll try again tomorrow. I did observe 48 knots just before touching down at Whiteman. I suspect position error, because that would imply a CL of 2.6. Doting father though I am, I cannot imagine that my flap is performing quite that well.

[October 2, 2009]

Flew Wednesday and today, staying in the pattern, trying to refine my landings with flap. It's apparent that even at 70 kias I'm still carrying too much speed on final; the plane floats quite a bit after I flare, even with the airbrake open. (On one touch and go I failed to retract the airbrake; it cut into the climb rate, but not dangerously. The main tipoff was buffetting due to separated flow in the wake of the brake.) The problem is that when I am flying alone the CG is so far forward that I can't trim for the proper approach speed. I think next week I will put some ballast into the baggage compartment in order to get the CG to a more natural position.

The flaps are working well, although they still do not extend fully; they stop about half an inch short of the end of the track. This is due to air still trapped in the hydraulic system; I expect that it will disappear over time, because some of it will get entrained as foam during each cycle and will end up in the bubble catchers. It appears that the flaps take 13-15 knots off the landing speed. The clean power-off stalling speed was 68 knots during initial flight test; the 200-pound weight gain since 2002 would increase that by about 5%, or 3 knots, at 2,000 pounds. (Today the airplane weighed about 1,900 pounds.) It now seems to touch down at around 50 or 51. The additional weight has also taken a bite out of the initial climb rate. Back when I could fly at 1,750 pounds or less and used 40 in. Hg. for takeoff, the initial climb was 2,000 fpm or more; now I use just 34 inches and with the added weight see only about 1,500 fpm.

It has been suggested that the intermittent problem with the push-to-talk switch could be temperature related, since it tends to occur initially and then correct itself after some time has passed. That might point to the audio panel, since it is the only thing in the mic key circuit that changes temperature.

[September 28, 2009]

Tried to fly today, not having done so for almost seven weeks. First, the batteries were low and wouldn't turn the engine over. I started it with the help of my ground cart, which consists of a homemade creeper with a couple of ancient auto batteries on it. Under normal circumstances they have a combined voltage of 8.7, but if I connect my homemade charger to them -- the Oneirodyne Amazo-Charge, as my old friend Peter Christie would have said -- they start the plane right up. And did. I taxied out, only to find that the mic key again (this last happened at Santa Fe in June) would not key the transmitter. Frustrated, I returned to the hangar and, just to have done something useful, checked the #2 flap master cylinder, which I re-sealed last week, for signs of leakage. There were none. I then gave the mic key one last try. People like to say that the definition of insanity is doing something over and over and expecting a different result, but this is quite false, and in fact in this case the result was different-- the XMIT light on the radio came on. By this time it was getting late and the plane was already back in the hangar, so, to paraphrase Lillian Roth, I'll fly tomorrow.

I really need to find the solution to this mic key problem. It is not the key switch -- which is on the sidestick -- itself; the problem remains even if I insert a manual key in the headphone mic line. It always seems to occur after startup, not during the course of a flight, and it resolves itself spontaneously sooner or later. It is as if an electrical bubble had gotten caught in one of the wires -- but there is no such thing as an electrical bubble.

My reading about Kelly Johnson and the Skunk Works has reminded me that many of the most satisfying days of my life have been spent on my airplanes, working from handwritten notes or scribbled sketches, and using the airplane itself as a mockup -- all techniques espoused by Johnson in contrast to the highly systematic and formal ones customary in aerospace. He tried to replace the drudgery of the factory floor with the excitment of the home workshop, and the oppression of the group with the passion of the individual.

[September 22, 2009]

There was nothing very mysterious about the leak in the #2 flap master cylinder, as it turned out; the static O-ring that seals the two parts of the cylinder when you screw them together was torn nearly in half in not one but two places. Oddly, it looked fine in its groove when I opened up the cylinder, and even after I removed it. It wasn't until I twisted the ring 90 degrees out of its natural set that the rip suddenly appeared. The damage must have happened during assembly. A new O-ring cost $1.35; some airplane parts are cheap. I wasn't sure how to lubricate it for re-assembly, but finally decided to leave the groove dry and to grease the inner faying surface thoroughly. I'm not sure that made sense; time will tell. Everything worked fine when I put it back together, but it will take a few cycles to know for sure.

[September 18, 2009]

I got back to the airport today for the first time since returning from the East on Tuesday. The hangar was as changeless as an Egyptian tomb. I hesitated to take the flap synchronizer apart in order to repair the leaks, since I expect to need to use the airplane next week, and I am very busy researching an article on Kelly Johnson, of Lockheed Skunk Works fame, for the Smithsonian's Air & Space magazine. I finally decided to go ahead, and managed, in the course of three hours, to repair the small fifth cylinder whose job is to restore everything to proper alignment after each flap retraction. The inside of the cylinder was badly scored, I'm not certain why, but it may have been galling between the aluminum piston and the aluminum cylinder. I ended up replacing the tube -- twice, actually, since I hastily drilled some holes in the wrong places the first time around. That's par for the course for me. I hope the #2 master cylinder, which drips, will be easier to fix; I suspect it's just a matter of a twisted or damaged O-ring, or some crud that got under the O-ring in my negative clean room.

[September 4, 2009]

We are staying in a friend's house at the mouth of the Pamet, a pygmy river that rises a stone's throw from the Atlantic near the tip of Cape Cod and flows three miles westward into Massachusetts Bay. Each evening Nancy and I go down to the harbor a little before the sun sets, walk some distance up the Pamet, and then turn as the sun vanishes below a small dune and walk back, stopping to admire the seabirds feeding in the slack tide and the ineffable mother-of-pearl palette of cloud, sky and water. We come here every year, and every year before coming I make a mental list of the things I am going to accomplish while here -- new or improved features in my computer software, a chapter in a never-finished book about the first Melmoth, the missing 20 percent of a film script that I wrote several years ago and that concerns, strangely enough, a pilot -- it's sort of Shane meets Medea, with wings. Each year, I do none of these things, falling, instead, into a daily cycle of shopping, cooking, reading, making minor house repairs and going to the beach, a routine that somehow swells to occupy every second of the time. This evening from our vantage point along the river we could see our son on the distant stone breakwater, casting for blues, a tiny erect figure against the twilit sea. He had waded across the harbor to get there, and probably underestimates the difficulty of returning in darkness, which is gathering as I write this. But he is a resourceful fellow, and will be back in time for dinner. He would not miss a lobster risotto.

[August 20, 2009]

I'm going away Saturday night for three weeks on the east coast, and leaving the plane here; so there will be a slack period in this otherwise gut-wrenching narrative. Because of having a lot of writing to do before leaving, I have not been at the hangar as much as usual; so I went there today to secure a few things, put tools away, and have a last (for a while) look at the plane. I did a little wiring, just to feel that I had accomplished something, and made a list of things that will need to be taken care of when I return, including the hydraulic leaks, the obligatory bi-annual static certification, and the glideslope receiver, which has stopped working. And, of course, I must figure out how to make lenses for the wingtip lights, and build the flasher circuit that Paul Lipps designed. At the rate I go, all this should take me well into November.

[August 14, 2009]

The #2 flap master cylinder is leaking again, as is the mysterious "driver" cylinder that is responsible for getting everything back into alignment at the end of each flap cycle (see diagram at October 13, 2008). For that matter, the airbrake cylinder has been leaking for a while too, so I have a bit of maintenance to catch up on. I don't remember the first Melmoth being quite so hydraulically incontinent as this, but I continue to believe that once I find and correct the cause of every leak, the system will cease to require much maintenance. At present, three of the four master cylinders are bone-dry, as are both inboard flap actuators and possibly the left outboard one as well. None of the connections in the plumbing is leaking any more, and not a single nylon line has blown out in the past two or three weeks -- this must be some sort of record. The right outboard actuator still seems to leak a bit. I tentatively attribute the proneness of the outboard cylinders to leak to their being subject to side loads, although I provided quite a lot of lateral slop where they connect to the flaps. Well, not for nothing does the airplane have "EXPERIMENTAL" written on the side of it.

[August 8, 2009]

Yesterday I took our daughter Lily up in the plane; she was the last remaining family member who had not flown in it. We moseyed around the west end of the San Fernando Valley at 4,500 feet, crossed the Santa Monica Mountains to Malibu, circled over the ocean and retraced our steps. I was in a quandary as to whether to tell Nancy before we did this, and decided not to. There was no good solution; she was going to be unhappy about it either way. I didn't, and she was, but we got back alive, so there wasn't too much to complain about. Lily liked it, and started talking about family trips to Baja -- "as soon as the drug war is over."

I saw the South African guys on Thursday, a few hours before they took off for Hawaii. They made it in 21 hours. Nice chaps. They are going to be over water practically the entire remainder of their return to SA, but they have only one more leg left that's as long as the LA-Maui one.

[August 2, 2009]

I got the bulbs from a downtown warehouse operation that didn't even have a sign outside, although it has a brightly-colored web presence. It was fun, something like venturing into a Moroccan souk. But I didn't work much on the plane last week because I was writing an article about Steve Fossett's accident and also fixing bugs in Loftsman that John Roncz uncovered in the course of designing an oddly shaped little aircraft. I finished the wingtip light assemblies and barely began making the tooling for forming the acrylic lenses for them.

On Wednesday I'm supposed to go down to Torrance to chat with a couple of South African guys who are flying around the world in an LSA they are promoting. They must have lots of Sitzfleisch -- long-suffering buttocks -- the longest legs for the 120-mph airplane being on the order of 24 hours. They're supposed to leave Oshkosh for Los Angeles tomorrow, and LA for Hawaii on Thursday. They have a website that tracks their progress.

[July 25, 2009]

The project du jour being the tip lights, and the halogen bulb sockets used by Grimes appearing less and less suitable as I chopped more and more off them to make them fit behind the position light bulbs, I finally abandoned them altogether and began searching on line for a substitute. In due course, having visited several ghostly online catalogs without benefit of phone number or geographical location, I identified, from their mug shots, some candidate sockets. It happened that at the same time I was repairing our washing machine, which had begun to leak water from the siphon break in its "injection hose" -- for such is the rather grandiose name of the rubber hose that delivers water into the tub. Searching, again, on line, I found the part, but it appeared that its cost would be nearly doubled if I wanted to have it in my hands in less than a week. Casting my memory back to the days when one turned to the Yellow Pages for appliance parts -- Los Angeles is, after all, a largeish city -- I resorted to that moldering volume and quickly located the hose a few miles south of my house. Encouraged by this experience, I began to hunt around for halogen sockets the same old-fashioned way, and was soon directed to a certain hardware store three miles from my house, Virgil's, which, remarkably, had a whole drawer full of a socket that looks just right -- though the sales personnel assured me that I must be mistaken about wanting a 24-volt bulb, since there was certainly no such thing in existence. Actually, there is. Twelve and 24-volt circuits seem to be used in outdoor lighting, no doubt so that dogs can urinate on the fixtures without dramatic effect. It is odd to notice, by the way, that these so-called 6.35 mm bi-pin bulbs cost, say, $3.99 each in one on-line catalog, and $7.99 in another. In fact, at the place where they are $7.99, everything is $7.99, including the sockets that I got from Virgil's for $3.19 apiece.

[July 20, 2009]

Yesterday I flew to Catalina with a couple of friends -- the landing fee is now a flat $25, so I don't go there much any more -- and on the return trip let one of them fly. He is a professional pilot and experienced in small aircraft (just "airline pilot" is no guarantee a person can land even a C-172). It is usually instructive to have another person fly the plane, and this time was no exception. One thing I learned was that it is apparently customary in this world for the mic key to be a trigger on the front of the stick grip. I have such a trigger, but it is the autopilot interrupt; the mic key is a thumb switch on the side of the stick. So Hans's first few transmissions went nowhere, because he was clicking the wrong switch; but it sounded as if he were transmitting, because the intercom was providing the expected sidetone.

When I take off I usually use 34/2800 initially, then come back to 30/2500 to climb. (Maximum T/O power would be 41/2800.) I habitually reduce power before raising the gear and flaps. But Hans maintained 35/2800 much longer than I normally would, while remaining at a relatively low climbing speed (80 knots with takeoff flap) and I noticed that the #3 CHT (right middle) got up to 240 C (464 F). It was a hot day, about 30 F above standard. It was still hotter at Whiteman -- around 100 when we took off -- but because of my habit of early power reduction and acceleration to 100 kias, the CHT had not gotten above 400. This made me realize that although I consider my cooling system satisfactory, it may actually not be adequate for a protracted climb at high power and low speed on a hot day. I don't know if production planes are any better, but it seems to me they must be.

We used 25/2200 for a leisurely return trip at 4,500 feet, indicating 126 knots at 6.5 gph.

[July 16, 2009]

On cutting the notch for the position light in the right wingtip, I found that much of the blue foam core in the curved transition from the wing panel to the upturned tip had been eaten away by gasoline that sometimes splashes out the tank vent during fueling. I recognized the look immediately, because a few weeks ago Mike Melvill had shown me similar gasoline erosion in the wings of his LongEZ. As it happens this doesn't matter much, since the tips are strong enough even without the core, and in fact I had deliberately carved out a similar portion of the core in the root of the left wingtip when I put the roll trim servo there. The vents open into the cavity between the wing and the tip, which is pressurized with a small flush inlet in the lower surface and vented to ambient pressure at the aft end; the idea was to provide a vent that did not protrude from the wing and would not ice up. It should have been obvious to me, after seeing Mike's wing, that something similar must have been happening in my tips; but I didn't make the connection.

I will build up the front of the core again, this time with fuel-resistant foam, lay up a shear web over it to restore the stiffness lost by cutting the hole, and then mount the light assembly on a floating rib running fore-and-aft. The light, here still in the pliers and tin snips stage, is basically just the standard Grimes unit with the back end of the teardrop cut off and the halogen bulb socket turned crosswise and crowded up against the nav light lens to make the whole thing as short as possible.

[July 14, 2009]

The position lights won out, since I'm still not sure which direction the pre-swirl for the turbo inlet should go. I'm heavily modifying a set of Grimes wingtip lights that I happen to have -- heaven knows why or where I got them -- and putting them under clear lenses where the wing transitions from a straight taper to the upturned dihedral-enhancing tips. There's just barely sufficient room. I'm not sure yet how I will form the lenses, but I will find out in due course, no doubt after ruining and discarding a great deal of Plexiglass. There will also be small white halogen bulbs that will blink -- a sort of poor man's strobe. I don't as a rule fly at night, but for such a complex airplane to be without lights seems incongruous.

This being Bastille day, the music station that I usually have on at the hangar played a rousing Marseillaise, all four or five stanzas -- I lost count. (We forget that the Star Spangled Banner -- a splendid anthem, in my opinion -- also has a whole bunch of extra stanzas.) The refrain of the Marseillaise includes the words "Qu'un sang impur abreuve nos sillons!" -- a remarkably sanguinary sentiment that, roughly translated, means "Let the foreigners' blood irrigate our furrows!" Actually, it doesn't say "foreigner" -- the exact words are "impure blood" -- but one gets the idea. I'm not sure which brand of blood was meant when the words were written in 1792; Prussian, perhaps, or Austrian.

[July 10, 2009]

After fixing a few small things, including a loose connection on the #1 CHT probe and a broken wire on the induction air temperature probe (which has not worked for years -- not that it mattered, since I never use enough boost to worry about excessively hot intake air anyway) I started making a mold for a new turbo inlet box. The turbo air inlet faces aft and is only a few inches away from the firewall; air coming into it has to make a sudden 90-degree turn. Currently, I'm using a "banjo box" to accomplish this -- although it would better be termed a "lute box." This is an expanding chamber with the turbo inlet bellmouth on one side. The idea is that air slows down and spreads out on entering the banjo box, and then gets sucked into the bellmouth. At some point I started to think that on the analogy of a tub drain, the right-angle turn might be made more efficiently if it relied on a spiralling path, like that of the turbo scroll itself. There is some question in my mind about whether introducing some pre-swirl into the inlet flow will mess up the impeller aerodynamics; but the turbo is usually running so far off point anyway that it may make no discernible difference at all. Anway, the idea of the whole project is to improve the breathing of the turbocharger. Actually, I should be working on navigation lights; maybe I'll do both projects simultaneously.

[July 2, 2009]

A benefit of seldom washing the plane is that the dirt on it forms streaks when I fly through moisture, and those streaks tell something about air flow. Today I noticed a faint streak that ran along the left side of the fuselage, starting a couple of feet above the wing. It paralleled the wing surface nicely, then went more or less straight aft for several feet before taking a little jog upward just before the baggage compartment door. The jog puzzled me for a moment, and then I realized that it was caused by by leakage around the door. The leakage is not outward, as you might expect, but inward, because the pressure in the cabin is lower than ambient, being dominated by outward leakage around the windows. This is why cabin vents should not be placed at the back end of the cabin; the pressure there is comparatively high, whereas the pressure in the vicinity of the largest cabin cross-section is low.

[June 29, 2009]

Yesterday we flew back home from Little River. The trip used 23 gallons to go about 420 nm, which works out to 18 nmpg. It's interesting to see how different the block mileage is from the instantaneous mileage. For most of the flight the engine was using about 7.7 gph, at a shade above 50% of power. Our true airspeed was about 159 knots, and so our mileage ought to have been better than 20 nmpg. We had light headwinds, about five knots at the start of the trip and 10 near the end. We did do quite a lot of climbing; we started at 9,500 and eventually ascended to 13,500, where the density altitude was 16,500, for a better ride. I suppose that the time spent climbing at 120 knots groundspeed cut into the mileage, and of course taxiing, runup and takeoff (27 gph!) do too; but I'm still surprised that the difference should be so large. I lean to 25-50 LOP immediately after takeoff and climb at 60% power or so, and 500 fpm. Maybe this is not actually the most economical way to gain altitude. The thing about climbing is that the rate really doesn't matter, because the work required to raise a certain mass to a certain height is a fixed quantity, regardless of how rapidly the job is done. (I was reflecting, as I repeatedly climbed the 85 steps from the beach to the house where we stayed north of Fort Bragg, that our sense that the rate at which work is done affects the total amount of energy expended is due to the way our bodies tire when we work rapidly but don't when we maintain a slower pace.) What affects the cost of climbing to a given altitude is the aerodyamic efficiency of the airframe and the specific fuel consumption of the engine. The aerodynamic efficiency is best around the best rate of climb speed, so that tends to take care of itself so long as you don't cruise-climb (but cruise-climbing may result in a shortened trip time; I haven't looked at that question, which is related to the Carson Speed, since the CAFE races in the 1980s). The specific fuel consumption improves as power output rises, and so it should really be more sensible to climb at a higher power setting, provided that the mixture remains the same.

It might, incidentally, be possible to recover most of the energy expended in climbing by shutting off fuel to the engine and allowing it to windmill with open throttle and coarse pitch during the descent; but passengers could object.

[June 23, 2009]

We got up at 5:00, took off at 6:09, and landed at Little River exactly three hours later, having enjoyed smooth air and a steady tailwind. Everything -- the GPS tracker, the mic key -- worked, except, of course, the flaps. The unreliability of the flaps is troubling; I will probably end up replacing all of the nylon lines with real aircraft stuff, even though it's so damn expensive. What was so odd about this failure was that it occurred when I was extending the flaps before takeoff, and there was no air load on them at all.

In this picture, taken as we crossed the Sierra Nevada into California, if you knew the geometry of the airplane you could infer the time of morning from the shadow of the horizontal tail on the wing. The Steve Fossett crash site is out there somewhere, probably behind the trailing edge.

[June 22, 2009]

I am writing this in Cedar City, Utah, where Nancy and I stopped for lunch on the way from Santa Fe to Little River, at Mendocino on the California coast north of San Francisco. We ran into quite a lot of turbulence on the way, and since turbulence is not Nancy's favorite part of flying -- actually, the only part of any flight she likes is parking at the end -- we decided to stay here tonight and leave at the crack of dawn, when the sun has not yet begun to heat up the desert surface. The plane had a couple of glitches at Santa Fe; the press-to-talk switch on the stick stopped working, and a borrowed substitute wouldn't work either. I arranged for a takeoff clearance by cell phone, but when I pulled up to the runway the transmitter resumed working, for no apparent reason. Then, just before takeoff, as I started to extend the flaps, I heard the dreaded pop and saw that the left flap was deploying unevenly. Evidently another one of those infernal NyloSeal fittings had blown off. So no flaps for the rest of this trip. Then the GPS tracker refused to recognize the GPS; it does that from time to time, again for no apparent reason, and pulls itself together on the next flight. And it appears that there is still a very minute fuel seep at the middle flap track on the right wing. I'll probably just live with it; sometimes leaks seal themselves.

June 13, 2009]

Having repaired -- I hope -- the leaks, I put the wing back onto the airplane at the end of the week.

Knowing, now, that one wing weighs 92 pounds, I was able to calculate the actual limit load factors for various fuselage loadings. Each wing, according to my 14-year-old dot-matrix computer printouts, was designed for an ultimate lifting load of 6,450 pounds, distributed spanwise in a manner halfway between a semi-ellipse and the geometric shape of the wing. This results in a moment of 386,000 inch-pounds at the outermost attachment bolt. Adding the weight of the main landing gear (35 pounds each) and the protruding portion of the centersection (which is integral with the fuselage), I arrived at a deduction of 135 pounds. Doubling all of this, so as reflect the whole airplane rather than just half of it, I subtracted 270 pounds from the measured (well, partly measured, with a small increment for the weight of the flap synchronization system) empty weight of 1,585 pounds, and got 1,315 pounds for the empty weight of the fuselage. (Even knowing the answer, I doubt I could come up with a weight breakdown that would account for it.) Then, I considered three loading conditions: single pilot, two 190-pound persons with 100 pounds of baggage, and four 170-pound persons with 50 pounds of baggage; these add, respectively, 200 pounds, 480 pounds, and 730 pounds to the fuselage weight. Dividing the three totals into the lifting load of 2 x 6,450 or 12,900 pounds, and dividing again by the conventional safety factor of 1.5, I arrived at limit load factors of 5.7, 4.8, and 4.2 G respectively. Weight creep -- or faulty estimation during design -- took its toll; I had intended, originally, that the plane be acrobatic at some loading. It falls slightly short, but no matter -- I am not particularly acrobatic myself.

I am aware that these numbers are slightly optimistic, because the weight of fuel is not uniformly distributed spanwise unless the tanks are full -- that is, unless I have won the lottery and put 142 gallons of fuel into my tanks. Partial fuel weight is concentrated inboard, and so it imposes some additional stress on the wing. The more fuel there is the more it spreads outward, however, and, although I have not yet run the numbers, I feel pretty confident that no fuel load could push the limit load factor, even at the maximum fuselage weight, below the Normal Category value of 3.8 G.

[June 5, 2009]

With the help of Russ Hardwick I removed the right wing in order to fix a couple of small fuel leaks. At the same time, I intended to calibate the fuel quantity senders. There are two in each wing, one inboard and one outboard, and in order to calibrate them it is necessary to be able to alternate between full and empty a few times. This is most easily done, obviously, by flipping the wing over. I also wanted to weigh the wing, in order to be able to calculate the actual weight of the fuselage. The senders are now calibrated, and the wing turned out to weigh 92 pounds, which is quite a bit more than the 52 pounds it weighed without tips, ailerons, flap tracks, controls, filler and paint.

The wing was easy to remove, once I had disconnected all of the electrical, hydraulic and fuel lines and the mechanical controls that connect it to the fuselage. After six and a half years, the faying surfaces showed no sign of fretting or corrosion. The main spar joint consists of two groups of 3/8-inch high-strength bolts, and it seems likely that under normal conditions friction due to clamping action, rather than the shearing strength of the bolts, transmits the load from the wing panels to the centersection. The outboard joint has four bolts and the inboard only three because the lift force is shared between them, whereas the bending moment is upward at the outboard attachment and downward at the inboard. The strips of reddish-brown color along the upper edges of both the wing and the centersection are non-structural; in order to reduce the cabin height, the centersection spar, which is made of carbon fiber and is black, is not as deep as the root profile, but only deep enough to contain the landing gear, which retracts under the seats. The four nutplates on the centersection spar are for the bolts that hold the front landing gear bearing block in place.

One simple rule that I seem to have been unaware of when I designed this wing is that there ought to be enough space between two structures to allow you to get your hand in. In this case, there isn't; to gain access to the fuel quantity sender, which is in the middle of the large round inspection plate, or to the low-fuel warning float, which is the little black thing in the recess, you have to remove the wing. Very clever. The three lines emerging from the tank are fuel feed, vapor return, and sump drain. I believe that the two shades of green on the aluminum reinforcing plate reflect the areas that were squeezed tightly together (darker green) and those that air could reach (lighter).

[May 31, 2009]

From time to time I have toyed with the idea of reversing the position of the intake manifold runners on my engine. The point would be to eliminate the transverse tubes which now obstruct the flow of cooling air toward the exits. For some mysterious reason this thought has come back to me with more force than usual, and I am thinking that I might actually do it. A little floor-based mocking-up exercise with tracing paper and the factory installation drawing, videlicet

has me thinking that it would not be very difficult or costly, and might yield a benefit in cooling drag reduction. The throttle and fuel metering valve, which are now on top of the engine and on the hot side of the baffles, would be behind it and on the cold side. There is still plenty of room ahead of the firewall for a pipe with a 90-degree bend going down to the turbocharger. The distance from the turbo to the throttle would be reduced by a foot or so. The main problem with the scheme is that it requires sawing up an intake manifold and reconstructing it with the orientations of two segments changed. That in turn requires finding a junked manifold, or at least the two curved front parts, since I would not want to destroy my present manifold in case the new version proved, for some unforeseen reason, to be unworkable.

I flew to Paso Robles yesterday with my friend Russ Hardwick. At 12,500 feet, density altitude around 14,000, speed was 174 knots at 8.4 gph.

[May 29, 2009]

Back from our trip east, I did a series of touch and go's today to get more familiar with the takeoff and landing checklist sequences and to get a better feeling for power settings, stick forces and so on during a pattern approach. (I usually fly a straight-in approach to Whiteman.) In the course of six landings, the lowest speed I saw before touching down was 52 knots, as compared with 68 knots without flaps. This suggests a CL of around 2.05 (1.2 clean). It's not clear how close to a full stall that was, and the flaps are stopping a little short of fully deflected because of small amounts of air in the hydraulic lines, so the figure of 2.2 that I mentioned earlier may yet prove to be correct. As always with high-lift devices, however, the exact CLmax is less important than controlling the flare, touchdown point and braking to minimize the required field length. I was able to trim to approach speed (about 73 knots) with takeoff flap (10 degrees), but with full flap (30 degrees), which I used only after turning final, I had to hold some back stick to keep the speed down. The CG was very near the forward limit. Fifteen inches of manifold pressure gives a good 600-700 fpm descent in the pattern with 10 degrees of flap. It appears as if I have a little too much speed on final. If touchdown speed is 52 knots, I should be flying the approach at 67 knots (1.3 Vs). It may be that the angle of attack indicator is not correct when the flaps are extended. But 73 knots is just 1.4 Vs, and it's easy to bleed off the extra speed by cutting the power and starting to flare a little early.

[May 15, 2009]

What was I thinking? Of course it isn't "done." No lights yet, the glideslope is inop, no gear position indicators, wings leaky and incompletely painted, no wastegate. Here is a to-do list which I began in 2002, before the plane first flew. When an item got done, I moved it to the end of the list and changed the font.

M2 to do

left front armrest
extend right console down to floor to prevent fouling torque tube
move aileron hinges
make left main gear doors flush
gear sway brace overcenter lock indicator lights
enlarge turbo banjo box
outboard sender, nav, strobe wiring
mechanically attach root fairings

remove wings:

calibrate all 4 senders
fuel leak in right wing, high, near root
fuel leak at right outboard sender?
fuel leak at middle track
why are low-fuel warning senders weird?
sand, smooth and repaint undersides

toe deflectors above brake pedals
replace nose gear actuator link
replace nose gear retract link
replace nose gear strut?
paint window margins
finish hard static plumbing
cabin/panel lights
nav lights
rotating beacon
alternate static
gas springs for main gear downlocks
canopy seals
window retention screws
adjustable wastegate
smaller alternator
tape pulley brackets
wire colors reversed on pwr/gnd from panel to alt/batt
oxygen system
NG actuating cylinder leak

**********************************************************************

Done

transponder
fuel flow/totalizer
static ports
oil separator
pitot-static-transponder certification
change oil and filter
swing compass
install nose strut gas spring
fit and install middle gear doors
correct position of inboard gear doors; why low?
new tow points
new tires
troubleshoot manual lowering
install and plumb nose gear cylinder
adjust gear control cable tension
reflector plate above cowl floor below turbo
reflector plate on air box
reinforce floor under torque tube support
repair cowl floor under turbo
enlarge cowl inlet
oil cooler radiation shield
overhaul Dukes pump
passenger seat
safety window hinge pins
gas springs for windows
fix short in radio rack
repair and revise turbo mount
put pop rivets in window latch mounting plates
provide cowling water drains
install #2 comm, both navs
replace anti-arcing diode on starter solenoid
move oil separator
fair cowl outlets
NAV antenna
hydraulic reservoir overboard drain
install autopilot
install rear armrests
seat upholstery
engine mount front fairing
reinforce right aileron torque tube support
wing trailing edge skin reinforcement
move air inlets to corners of engine mount
seal around exhaust pipe
carpets
contour wing upper surfaces
service EGT
service artificial horizon
service autopilot
fill and fair wing joints
paint removable parts
paint
reinforce floor under brake pedals
bracket to hold down right baffle shelf
replace leaking brake fluid hose
check voltage regulator wiring per Lipps letter
bracket to hold air duct away from exhaust
prime interior
seal holes in firewall
replace Lord mounts
longitudinal restraint for turbo
straighten lower end of nose gear half-fork
straighten NG retract link
reinforce or replace NG retract link
tiedown rings
electric tank switcher
get artificial horizon
revised turbo inlet air ducting
shift gear lowering backup hex
airbrake
use balsa core for cowl outlets
add camlocs to top cowl
cabin heat
rudder trim tab
#2 comm antenna
floor under rear seats
wingtips
shim front engine bearers
move fuel distributor
display compass card
stall warning horn
provide ventilator valves
repair #2 VOR
12 v outlet
glideslope antenna
marker beacon antenna
improve battery heat shield
replace voltage regulator
repair and reinforce battery connections
battery box insulation and blast tube
flap root fairings
boarding step fairings
move pilot's ventilator to panel
NACA engine air inlet
airbrake warning light
rear seat rails
outboard flap track fairings
airbrake position indicator
install GPS tracker
revise trim system
shimmy damper leak
nosewheel doors
rear seats
make cowl outlet ramps movable
pilot's seat
intercom
GPS rack
exhaust gas deflector plate w/afterbody
outboard flap actuator plumbing
back seat ventilator
roll trim
fill and fair grooves around windows
make new middle flap tracks
flap synchronizer
reinforce middle flap track attachment area
reinforce inner wing skins

A couple of the not yet done items deserve clarification. The nose strut is sufficiently strong, but the diameter of the piston (1.25 inches) is on the small side, and as a result it is difficult to pressurize correctly; either it is too soft and tends to bottom, or it is too stiff and tends to extend fully and stay that way. I have a vague plan of revising one of the old main struts from Melmoth 1 to serve as a nose strut; the piston's diameter is 1.625 in., and it should be less sensitive. I think the turbo would breathe better if the banjo box, through which air entering it makes a sudden 90-degree turn, were larger and differently configured. The wing root fairings are currently held in place mainly by aluminum tape; the idea was to use screws, eventually. As for the wastegate, it is currently the fixed type, with the result that the air throttle butterfly is often partly closed; I think that efficiency would benefit from having the butterfly open and regulating power with the wastegate; but I'm not sure about it, or how big a difference, if any, it would make.

[May 12, 2009]

Leaving tonight for the east. I'll be away two weeks. Someone asked me the other day whether the airplane was "done." In a way it's never done, but I had to admit that, in terms of what I set out to do, it's done. Oops -- no oxygen system yet! Not done yet -- thank God!

[May 6, 2009]

I made a short flight today, and encountered an interesting phenomenon after landing. A good wind was coming down the runway; the ATIS was calling it 10 with gusts to 15, but from the windsock I would have judged it to be more like a steady 15 knots. Anyway, after touching down I wanted to make the first turnoff, but when I applied the brakes the tires just seemed to skid. I had never encountered this behavior before and didn't understand what was happening until I thought about it again a couple of hours later. It was the flaps; even with the airplane in a level atittude they were taking enough weight off the main wheels that I was not getting effective braking. In order to make a short field landing, I would have to retract the flaps as soon as the wheels are on the ground -- equivalent to airliners raising their spoilers after touchdown. Just have to be sure to grab the right handle. (I made the turnoff anyway.)

My passenger pointed out that I still had a hand-lettered sign next to the flap handle saying "FLAPS (INOP)". Before leaving the hangar, I put a little acetone on a paper towel and erased it. The flaps are definitely working.

[May 4, 2009]

I drained the hydraulic fluid from the #2 master cylinder, replaced the Nyloseal fittings with AN flare fittings, pressurized it with air, submerged it in a bucket of water, and found that it did not leak a bit. The suspect joint between the piston and the shaft is evidently tight after all. The leak must have been at one of the two Nyloseal fittings. I re-installed them with more teflon tape, but I'm not confident of that being a permanent fix. Still, the news was basically good; if this cylinder is free of structural leaks, the others probably are too. Sooner or later, one can always get the better of leaky fittings.

Speaking of leaks, after reflection I decided not to take the leaky wing off this week. Nancy and I are going to the east coast next week (not in Melmoth -- too expensive) to introduce ourselves to our granddaughter, who was born on April 21. That would have given me only a few days to work on the wing. Instead, I will wait until after a certain event on May 30 to take the wing off; I will then have a couple of weeks to work on it before needing the use the plane again.

[May 2, 2009]

Nancy and I spent Monday through Thursday of last week visiting friends who have a house in the Sierra about halfway between Fresno and Yosemite. On Friday I removed the leaking master cylinder from the flap synchronizer, but did not have time to do anything with it. It's not actually clear where the leak is -- I thought it was at the main joint where the two pieces of the cylinder join, but I found some fluid inside the piston shaft, which would mean that the threaded joint between the piston and the shaft, which I sealed with Loctite and tested with compressed air, has begun to leak. Having found this apparent leak on the cylinder I had removed, I checked the others and found a drop of fluid at the end of a couple of other piston shafts. The floor below them was dry, so those leaks, if leaks they be, are very slow. They would be comparatively easy to repair, in any case, but I'm not certain that this is the only leak in the cylinder that I removed.

I'm planning to remove the right wing next week to deal with several fuel leaks, including one that kicks in whenever I put in more than about 25 gallons of fuel. I have not had a wing off since spring of 2002; it will be interesting to peer into all the dark places and see how they're doing.

[April 22, 2009]

A milestone of sorts: after six and a half years, Melmoth 2 finally flew with four people aboard. Mike Melvill was in the left seat. Ray Henning and his friend Mary Cunningham rode in the back seats, whose acrobatic entry procedure they accomplished with a good grace. We flew from Tehachapi down to Shafter, north of Bakersfield, where we picked up Ray's T-18 to bring it up to Mike's hangar. It will be stored there until it is sold. Mike has a lot of pictures up on the walls, and he gave us a tour, reminiscing about some of his adventures, which include a 38,000-mile circumglobal flight with Dick Rutan, mostly over water, in two Long-EZs. I thought it was remarkable to reflect that this entire career, this extremely rich life, had been set in motion many years ago by the decision of Mike and his wife Sally (who had eloped and married in their teens) to send away for plans for a weird-looking airplane designed by an unknown character named Burt Rutan.

[April 19, 2009]

Yet another video. This one is from the first up-and-away flight, on November 1, 2002. (I had made three short runway hops the day before.) The reasons for the weird temperatures that cut the flight short were two: the oil cooler plumbing was messed up, so that no oil was going through the cooler, and the selector switch that toggled between oil and induction air temperature readings, which share a single instrument, was mislabeled, so that the extremely high oil temperatures appeared as air temperatures, and vice versa. The high oil temperature was the cause of the drop in oil pressure. My comments, after landing, that the engine seemed to lack power are in the category of first-flight observations that are forgotten later. The drag of the landing gear must have made me feel that the airplane didn't have much pep. Anyway, it's never seemed that way since; it has plenty of power. Indeed, except for takeoff I never even use power settings as high as 30/2500 any more.

[April 17, 2009]

I should have added to the discussion below that since the maximum possible lift coefficient of the flapped portion of the wing is much higher that that of the unflapped portion, it would seem that the most likely point for the stall to begin would be just outboard of the flap. It remains to be seen whether this is the case.

In the meantime, now that the flaps, which have occupied me for so long, are working, I have sunk into a sort of pastoral stupor. The only thing I did on the airplane in the past few days was to mount a tiny video camera at the tail; the idea is to tuft the underside of the horizontal and see what the flow looks like during the approach to a stall, particularly with a forward CG.

I did post a couple of new videos on YouTube. Now that I have overcome my natural reluctance to appear ridiculous, I am willing to post just about anything. One of them, which only a parent could love, is of me pushing the plane into the hangar; the other, which is of slightly greater interest (if only because it contains an instance of that piece of film magic called a wipe), shows the extension and retraction of the Fowler flap.

[April 13, 2009]

The main reason for tufting the wing while testing the flaps was to get warning of an incipient outboard stall. It is often said that the outboard portion of a flapped wing is operating at a lower effective angle of attack than the flapped portion, and so the stall will not begin at the tip. Actually, the lift coefficient of the outboard panels is greatly increased by the upwash produced by the flap. Here are plots of spanwise variation of pressure coefficient along the quarter-chord line of the wing, without and with flaps. In both cases the angle of attack is zero. A negative pressure coefficient represents reduced pressure on the wing skin, a positive one increased pressure; lift exists when the pressure on the top of the wing is lower than that on the underside.

The numbers are hard to read, but the vertical scale goes from +1.0 (bottom) to -2.0 (top) -- it is customary to plot pressure coefficient with negative values going upward -- and the horizontal scale, which represents fractions of semispan, goes from 0 (centerline) to 1.0 (tip). The outboard end of the flap is at about .68 on the horizontal scale. The noteworthy things, I think, are that the lift increment supplied by the flap does not drop off suddenly at the end of the flap, but declines gradually toward the tip; and that a significant portion of the lift increment due to the flap -- the lift can be visualized as the area between the upper and the lower lines -- takes the form of increased pressure on the bottom surface of the wing. When the flap is retracted, the lower surface pressure is uniformly negative; when the flap is down, it is largely positive, becoming somewhat negative only about a third of the way out along the aileron. These differences are due to the flap greatly accelerating flow over the upper surface, while retarding it over the lower surface; our old friend Bernoulli is at it again.

The influence of the flap is felt even across the fuselage; the pressure coefficient at the centerline is -0.6 with flaps down and -0.45 with flaps up.

[April 10, 2009]

The other day, when I was visiting with Burt Rutan, he came out to look over my airplane before I left, and remarked that he had done one of the first layups on it. This was true: He and Mike Melvill came down to Whiteman in August, 1981 and laid up the inner skins of the top and bottom halves of the aft fuselage. This was my introduction to wet layup; I took over from there. The tail cone, from the fin post bulkhead to about the trailing edge of the wing, was made by heating 3/4-inch thick foam sheets in a homemade oven to soften them, and then bending them and gluing them into place in a fixture consisting of particle-board cradles. After the inner skins had been laid up by Burt and Mike, I added frames, then joined the top and bottom. Finally, I sanded the outer surface to give it continuous longitudinal contours. The outer skin was done in my garage during the winter of 1981.

In the picture below, which was taken while I was still a tenant in the big hangar at Whiteman, the frames have been added and the top half has been lifted out of its fixture and set down upright on top of it. The slanted bulkhed in the lower half is the footrest for the back seats. At this point, I felt that I would be finished in another year or so.

[April 9, 2009]

I flew today with full flap. The trim change is not excessive, at least with 50 pounds of ballast in the baggage compartment. I haven't stalled it yet, but it appears that the stalling speed will be around 50 knots at a weight of 1,900 pounds; this corresponds to a CL of 2.2, which is about what I hoped to achieve. (Theoretical section coefficients like 2.8 and 3 reported for big Fowler flaps are two-dimensional values; the complete airplane doesn't do that well because only part of the wing is flapped, the flap has tip losses, there's a download on the tail, and so on.) The flap hydraulics remained pretty dry, with just a couple of remaining drips. Unfortunately there is a new fuel seep in the right wing where I added the track reinforcement gusset, but that shouldn't be too hard to fix.

[April 7, 2009]

I flew out to Mojave on Monday to visit Burt Rutan, whom I first met in 1975, before the first VariEze had been built. I used to see him for lunch very regularly, but I had not talked with him in a long time. He had lost 40 pounds last year and had a close brush with death from constrictive pericarditis, but he now looked sleek and rosy-cheeked. He spoke of the SpaceShipOne project in tones of fond awe and retrospective amazement, and expanded enthusiastically on the absurdities of some of his interactions with government agencies charged with regulating not-yet-existent technologies like thrill rides to space.

Today, I worked on adding a pressure relief valve to the retraction side of the flap hydraulics; I will finish that tomorrow. It appears that one each of the master and actuator cylinders is leaking; the rest aren't, so I feel that I am slowly gaining the upper hand.

[April 1, 2009]

Today I extended the flap to 20 degrees. The hydraulic pressure was close to the relief value setting -- 550 psi -- but the flaps seemed to be traveling freely. I had put a 50-pound ballast into the baggage compartment; this moved the CG to around 20% of chord and alleviated the out-of-trim condition created by the flap. The trim change due to the additional flap deflection was slight. Lots of hydraulic seepage, however, some of it coming from the master cylinders themselves, some from the NyloSeal fittings.

[March 31, 2009]

I realized after taxiing to the runway today that I had not removed the floor panel covering the flap synchronizer, and so could not see the temporary hydraulic pressure gauge. The point of the flight was to find out what pressure is required to extend the flaps fully. I didn't want to taxi back, so I flew anyway, climbed to 7,500 feet, and extended the flaps to 15 degrees. With the CG about as far forward as it ever gets and the airbrake (which produces a nose-up trim change) extended, there was insufficient trim authority to hold approach speed (70 kias); hands off, the nose came down to the "fast diamond" on the angle of attack indicator, that is, something like 1.4 Vs. More flap deflection will tax the trim tabs even more. It's hard to tell, at this point, whether this will be a problem worth doing something about. I could increase the chord of the trim tabs or, alternatively, only extend full flap on short final. One question, which I will be able to answer with a couple of sandbags once I am comfortable with full flap, is whether the trim shortage occurs only with an extremely forward CG. Another question is how much elevator deflection is required to hold up the nose with full flap; I put a gauge on the stick to enable me to read elevator deflection in flight.

[March 29, 2009]

In an attempt to stay abreast of the times, I have uploaded to YouTube a mercifully brief video of Melmoth 2 landing at Santa Paula, shot a few days ago by Paul Lamar, whom I was going to see. The title is "Melmoth 2 landing at SZP". The flaps are at the takeoff setting, and the airbrake is down. My daughter Lily, if she learns of this, will declare it the nadir of vulgar self-promotion.

[March 27, 2009]

I have been concerned about possible flap asymmetry in case of a failure of one of the NyloSeal lines. This afternoon I blocked the flap in place at about 15 degrees deflection and then ran the pump to try to lower it further. Sure enough, one of the fittings popped off. After cleaning up the mess I tightened all of the fittings -- some of them took a full turn or more, which surprises me since I thought I had tightened them pretty firmly when I first assembled them. I don't understand how you're supposed to know when they are properly tightened. When I get the whole system to stay together during, say, a 10-second run at the relief valve setting, which is 550 psi, I'll feel more comfortable about going past the takeoff setting in flight.

The left outboard flap actuator continues to seep fluid from the retraction-line fitting -- a pipe-thread AN fitting, not NyloSeal. I would despair of ever getting some of these fittings to seal if I did not have the example of others to show that it can be done.

Yesterday for the first time I tried a takeoff with the takeoff flap setting; the airplane naturally ascended in a flatter than usual attitude, and felt like an elevator.

[March 23, 2009]

This strange sight is not a structural failure; it is a static load test of the outboard flap track. The idea was to apply a lifting force to the end of the track using the floor jack (the blue thing), with a bathroom scale (the square white thing) between them. The red jack was following the wing without applying any force to it, so that it would not fall very far if the flap track failed. It didn't.

While I was crawling around under the wing I noticed that hydraulic fluid was leaking from the outboard actuator. I removed it and re-installed all the fittings, replacing one that had a deep longitudinal scratch of unknown origin in the conical portion of the male AN flare fitting. The procedure for debugging the hydraulics seems to be to keep dismantling and reassembling things until, for whatever reason, they stop leaking. They can then, I hope, be ignored for many years.

[March 19, 2009]

There's a TFR today that will preclude any flying.

I should clarify something about the flow separation I noted a couple of days ago. I did not make sufficiently explicit that the picture showing reversed flow over a portion of the wing root was taken at 85 kias, which is the flaps-up approach speed. Now, this kind of separation at approach speed has no operational significance. It would matter only if it still existed at the best rate of climb speed, which is around 100 kias at low weights, but at that speed the separation has disappeared. Its presence at the lower speed is of mainly academic interest. I suppose that the fact that the separation vanishes when the flap extends a few inches might have some relevance to the initial climb rate after takeoff, but that influence would be very slight and, again, operationally inconsequential.

I should also explain my use of the terms "approach speed" and "climb speed." Early in flight testing, Mike Melvill identified 68 kias as the power-off stalling speed. The pilot-static system has not been calibrated down to that low a speed, but it is generally accurate and so I assume that 68 kias is about right. It corresponds to a CL for the complete aircraft of about 1.2 at the tested weight. (This is rather on the low side, and might be attributed to the low Reynolds number of the wing at landing speed; the chord, just inboard of the upturned tip, is 20 inches.) Under the conventional definition of approach speed as 1.3 Vs, the corresponding approach speed should be 88 knots. I rely mainly on the Safe Flight angle of attack device to regulate my approaches, however, since it automatically compensates for weight. When I first installed it according to the instructions, which suggest a "typical" chordwise location of the sensing tab, it yielded an approach speed of 85 kias, which seemed close enough to 88 and provided a comfortable flare. The angle of attack instrument has three reference points on its face, corresponding respectively (and roughly) to a slow approach (1.2 Vs), a normal approach, and best rate of climb (1.4 Vs). The angle of attack sensor is on the flapped part of the wing, and so in principle it compensates for flap deflection, since what it is actually sensing is the direction and dynamic pressure of flow in the vicinity of the tab (which looks just like a stall warning tab). The indication is somewhat affected by speed, however, since if the airplane is heavier, say, or the flap is down and the airplane is moving more slowly, the pressure felt by the tab may be different even though the location of stagnation is the same. At any rate, since the AoA indicator is my primary reference for approaches, I am using it to define "approach speed." Thus, when I say that the approach speed is 10 knots lower with the flap in the takeoff position, what I mean is that the AoA indicator is pointing to the "approach" marker (a green band in the middle of the indicator), not that I have measured the stalling speed and then multiplied it by 1.3

[March 18, 2009]

Today I intended to begin extending the flap past the takeoff setting; this would presumably entail larger trim changes and higher hydraulic pressures during extension. When I retracted the flap after takeoff, however, I heard a pop. Sure enough, the same nylon fitting had failed as failed on the 13th. After returning I replaced the nylon line with an armored high-pressure Aeroquip hose, which won't fail. I'm puzzled by the pressure spike that is apparently occurring in the line going to the cylinder that is labeled "Driver" in the diagram under October 13, 2008. I can't see why it would see higher pressures -- and during retraction, besides -- than two other nylon lines that are in parallel with it. Maybe they will be the next to fail.

As expected, if I taxi with the flap extended the middle roller bounces against the track, making a disagreeable rattling sound.

[March 17, 2009]

After repairing the popped hydraulic connection yesterday, today I tested the flaps as far as the takeoff setting. At this point the leading edge of the flap has translated aft almost to the trailing edge of the wing, and the flap chord line is deflected about 10 degrees with respect to that of the wing. The transition from takeoff to landing flap involves little additional aft travel, but the deflection increases to 30 degrees. Here is the scheme at the inboard track, at BL 25, where the total travel is 14 inches:

The takeoff setting reduces the approach speed, as indicated by the Safe Flight lift meter (alias angle of attack indicator), by 10 knots. I don't know what the reduction in minimum speed is, but the flap made a remarkable difference in the landing rollout. Without flaps (that is to say, for the past six and a half years) I have turned off Runway 12 at Whiteman at the third taxiway, with heavy braking; today I turned off at the second (at midfield) , and had to add power to get to it. Although I never minded not having the flaps before, now that I have them it would be difficult to go back to not using them.

At approach speed -- 75 kias with takeoff flap -- the flow attachment is good. Here are tuft shots with the flap about one inch short of the takeoff setting:

Interestingly (and disappointingly) this is not the case with the flap retracted; there is a pool of separated flow aft of 75% of chord, near the wing root:

Extending the flap a few inches improves this situation, but probably adds enough parasite drag to cancel the benefit:

There is still a great deal of testing to do.

[March 13, 2009]

This afternoon I finally operated the flaps in flight for the first time.

As far as it went, the experiment was an aerodynamic success but an hydraulic failure. Having slowed to approach speed (85 kias) at 7,500 feet, I extended the flaps, by small increments, to about half of the actuator travel -- the middle of the flap moved aft about six or seven inches while deflecting less than five degrees. This is much less than the takeoff setting, which involves about 11 inches of aft travel and 10 degrees of deflection. I had tufted the left wing and flap. At the approach angle of attack, I noted some separation in one tuft near the trailing edge of the wing at buttline 48. Even a slight flap extension reattached all upper-surface flow. The tufts on the flap upper surface were straight and steady. At half-extension, approach speed was reduced by seven knots. There was scarcely any trim change. I cycled the gear and the airbrake and did not observe any effect on the flap.

I then retracted the flap and extended it again. In the course of this operation one of the nylon hydraulic line connections popped off, flooding the area under the rear seats with hydraulic fluid and obliging me to return to the airport. The landing, with about four inches of flap extension, seemed unusually smooth and stable, but I may just have been paying more attention than usual.

Although the test ended prematurely, it looked promising -- particularly the lack of trim change, the good flow attachment, and the sizeable reduction in approach speed even with a fraction of the full Fowler travel. Some potential areas of concern are lifting of the long cantilevered slot lip, vibration or flutter of the flap, and flexing of the outboard track, which is an odd shape and difficult to analyze. The only sign of any problem that I observed today was lifting of the slot lip by maybe 1/4 inch. It will probably be necessary to anchor it at a few points.

[March 5, 2009]

Still no electrical power in the hangar, and since the temperature dropped about 10 degrees overnight the epoxy was too cold to pump and the filler on the wing surfaces was not yet sandable. I took off the cowling to inspect the engine, and found that one rocker cover screw had backed out and one exhaust flange nut had fallen off. Fixed those things. One convenience of updraft cooling is that since the bottom of the cowl has to be more or less airtight, stuff that falls off the engine stays in the airplane.

Last night, I figured out the relationship between the outermost shoreline of fuel, as determined by the fingernail tap test, and the amount of fuel in a tank. Here is the result:

Since the dihedral angle is rather small, the roll attitude has a fairly powerful influence on the results. The circled numbers are conservative, the actual values at buttlines 75, 92 and 130 being 6.5, 12.9 and 34.3 gallons, respectively. Those three buttlines were selected because they correspond to obvious landmarks on the wing; 75 is the middle flap track, 92 the angle of attack/stall warning sensor on the left wing, and 130 the outboard flap track. Now I have to decide whether to rely on memory, carry a copy of the chart in my flight bag, write the numbers on the underside of the wings, or all three.

[March 3, 2009]

I took 29 gallons of fuel from the right tank; with the 26 I took from the left tank a while ago, that makes about 20 gallons more than the totalizer said I had. I last initialized the totaliser 155 hours ago. Assuming an average fuel burn of 8.5 to 9 gallons per logged hour, the totalizer would be off by about 1.5% on the high side. My fuel quantity indicators are not overly reliable at any reading other than zero, so I can't use them to reset the totalizer from time to time. The only thing to do will be simply to add a gallon to the reading after every seven or eight hours of flying. The good side of this is that I am using less fuel than I thought, and so the airplane must have slightly less drag than I thought, since all of my power estimates, which are the basis of drag estimation, are based on fuel flow, and furthermore the plane has been heavier than I thought.

One of the difficulties of my fuel tanks, which consist of the entire interior of the wings, is that it is not possible to check fuel level visually. Since each wing holds 71 gallons, the tanks are never full or even nearly so. I noticed yesterday, however, that there is quite a difference between the sounds produced by tapping with one's fingernails on the underside of the wing where the skin is under fuel and where it is not. Since Loftsman allows calculating fuel quantity for any height of the fuel surface and any pitch or roll angle, it would be a simple matter to create a graph correlating approximate fuel quantity with the spanwise station at which the tapping sound changes.

I was so bold as to make a work schedule over the weekend. According to it I would be able to fly next Tuesday. All went according to plan yesterday, but today the electricity in the hangar was off, and that slowed me down a bit. I may catch up tomorrow, which, if the schedule is to be believed, will be a light day.

[February 26, 2009]

I've filled the holes in the upper surfaces of both wings with foam. It's been chilly in the hangar, and the microballoon paste that holds the foam cures rather slowly, so I haven't yet been able to sand the patches smooth and skin over them. I expect to get the foam filler into the hole in the bottom of the left wing tomorrow. I'll then move the fuel in the right wing into the left wing and add that final gusset. If things go well I should be able to skin all the other patches next week.

[February 18, 2009]

Dodged a couple of bullets. Returning to the hangar on Monday, I found the bolts that I had used to locate the lower-surface gusset too tightly bonded to be removed even with my largest screwdriver. Fortunately, I was able to get them out with a pair of channel-lock pliers, merely wrecking a couple of bolt heads in the process. Then, yesterday, I laminated the second ply of the gusset and two plies of carbon cloth into place, only to find that I could not maintain a vacuum in the vacuum bag, evidently because of the porosity of the fuel tank skin. So I cobbled up a sort of poor man's vacuum bag, consisting of a piece of foam rubber, a piece of plywood, and a wooden crutch pushing up against the plywood from the floor. This morning I found that the lamination had cured very nicely, and looked just as though it had been vacuum-bagged. Here is the completed gusset on the lower surface of the left wing:

The four bolts are bonded into place with JB Weld, a hard commercial epoxy that fills any voids between the bolt and the gusset. It now remains only to fill up the cavity with foam and skin over it.

Because of the difficulty I experienced in vacuum-bagging the lamination, I am changing the design somewhat. I will attach the second layer of each gusset to the first with the same Click Bond adhesive I used to bond the first to the wing skin, and then lay the two graphite plies over the top of both in lieu of passing one of the plies between them.

[February 13, 2009]

With rain roaring on the hangar roof, I finished digging out the sandwich core on the underside of the left wing and bonded the gusset into place. Sanding while semi-supine under the wing was no fun, but I found that by holding the vacuum cleaner nozzle between my drawn-up knees I was able to intercept most of the falling junk before it fell into my eyes and nose. I used a couple of wood crutches to hold the phenolic gusset in place during cure. Viz:

The procedure for this operation, once I overcame my reluctance to destroy the pristine surface of the wing, was first to cut through the outer skin with a very small grinding wheel in a Dremel-like tool, and then to pry the outer fiberglass skin away from the foam core. (This is one of the upper-surface gussets.)

Next, I dug out the foam with a chisel. This brought me down to the layer of epoxy-microballoon paste that forms the interface between the laminate and the core.

Using coarse sandpaper and a considerable amount of effort, I then sanded away the surprisingly durable microballoon layer. The inner graphite skin, which is the principal wing structure and also the liner of the 71 gallon fuel tank, was now exposed.

Finally, I bonded the gusset into place.

A second, shorter gusset will be added on top of the first one. The final reinforcement will consist of two plies of .100 phenolic with bidirectional carbon cloth between and over them and overlapping the exposed carbon surrounding the gusset. The extra thickness is needed not for compressive strength, but to handle the bearing loads on the four 1/4-inch bolts that join the gussets to the aluminum fittings within the flap cove. (The four holes are now 3/16 in diameter; they will be drilled and reamed when the complete gusset is in place.)

Finally, the outer skin surrounding the hole will be sanded to form a shallow scarf joint, the hole will be filled with foam and microballon paste, and a couple of plies of bidirectional glass cloth will be laid up over the top, dressed, and then, if past experience is any indication, clumsily painted. The whole procedure is repeated four times

[February 12, 2009]

A slight bump in the road. After bonding the upper-surface gusset to the right wing -- the acrylate goop cured much more rapidly today, no doubt because it was warmer than yesterday -- I began prepping the lower surface of the left wing. No sooner had I scraped away some of the foam core than gasoline began to seep out. Evidently the inner skin is somewhat porous, and it is the closed-cell foam core that is providing the final barrier to fuel leakage. There was no discoloration in the foam core, nor any apparent deterioration, so at least the fuel is not devouring the foam or migrating through it. (Auto fuel, with its aromatics, might be a different story.) I learned only after closing my wings that it is customary to coat the inside of integral composite tanks with a layer of pure epoxy. That would have involved a weight penalty of about six pounds, since the wing is entirely wet. In any case, draining 27 gallons of fuel from the wing into a collection of borrowed containers took me the rest of the afternoon. Tomorrow I should be able to bond the gusset on the underside of the left wing. I had intended to do each step of this operation at all four locations before going on to the next step, but evidently I will have to complete the repair to the left wing before draining fuel from the right wing and moving it to the left, which is my only remaining container.

[February 11, 2009]

Removing the wedge of outer skin and foam core from the wing proved to be remarkably difficult. This was gratifying; the sandwich is extremely tough and well-bonded. The outer skin, which consists of two plies of unidirectional material at right angles stitched together, 45/45 to the wing axis, had to be removed with pliers, and came off not as a sheet, as I expected, but in narrow, ragged strips, one layer at a time. The inner skin, the graphite one, is also hard as rock; I expected a little flexing, but detected none. Today I bonded the first gusset into place with the Click Bond stuff, which turned out to be easy to use. It's an acrylate adhesive, like Super Glue, but with a creamy consistency and a comparatively slow cure. You squish two components out of the envelope (I used three envelopes to be safe; I could probaly have gotten away with just two) and mix them up. They start off white, then turn yellowish as the reaction begins. By the time the goop has stiffened up, after 20-30 minutes, it is a dull green color. I was worried that I might end up permanently bonding into place the four clecos that I used to hold down one end of the gusset, so I kept taking them out, one at a time, and wiping them off. They seemed not to stick. Tomorrow I should be able to bond the second upper-surface gusset into place and get one, perhaps both, of the bottom surface holes prepared. I'm beginning to feel quite excited about the prospect of using the flaps.

[February 9, 2009]

The flaps and the middle track fairings are now installed. Apart from some minor seeps, the hydraulic actuation system is working properly. Many of the leaks involve the nylon hydraulic hose fittings, whose pipe threads are slightly smaller than those on AN fittings. After assembling a lot of the components, I found that several winds of teflon thread tape (which I first thought would be unnecessary because the fittings themselves are plastic) seem to prevent seepage, but I have not yet gone back through all the fittings to add the tape. The flaps still aren't ready to be used in flight, however. I have made the phenolic gussets that will be added, in a belt-and-suspenders sort of way, to the wing structure at the middle track attachments. All of my structural epoxy is quite out of date, and on Mike Melvill's advice I ordered a bunch of packets of Click Bond adhesive to attach the gussets. This is an adhesive used for nutplates, surface-mounted studs, and things of that sort, and Mike says it is exceptionally strong. These bonds don't actually have to be especially strong, because the load is spread out over a large area. Super glue would probably do fine. But if the stuff is really bulletproof, so much the better.

Installing the gussets will require removing a triangular patch of the outer skin, sanding down to the carbon inner skin, bonding the gussets to it, and then re-filling the hole and applying a new outer ply with a scarf joint to the existiing skin around its perimeter. The wing skin sandwich consists of a non-structure fiberglass outer ply, a foam (Divinycel) core about a quarter-inch thick, and a structural carbon inner skin. Hence the need to attach the gussets to the inner skin -- it is the one that carries most of the wing loads. This procedure should be quite easy on the upper surfaces, but difficult on the undersides of the wing, where I will have to work lying on my back with sanding grit falling in my face.

[January 28, 2009]

I took the flaps off the airplane in order to do the final laminations, attach the middle track fairings, etc. I won't get them back on until next week. Here is the middle flap track attachment. When the picture was taken the bolts were just slipped temporarily into place, but as of yesterday all of this is permanently assembled.

As I originally designed it, the upper and lower attachment fillings were a single piece; but I belatedly realized that in the event of the tension bolts at the bottom tearing out, the aileron pushrod would be jammed and the airplane would become uncontrollable -- which, indeed, it might be anyway if one flap went adrift. This attachment is at BL75.00, that is, 75 inches out from the airplane centerline; the flap extends from BL25.00 to BL140.00. The clevis-like object in the background is an idler supporting the aileron pushrod; there are a couple of these on each pushrod. They reduce the length of unsupported segments of the 3/4-inch diameter pushrod, which otherwise would not be able to take compressive loads without buckling. The 1/4-inch aluminum tube with the wire tied to it is the pitot line; the pitot head is located near the tip of the left wing.

[January 20, 2009]

Discedit frutex, ubi patriam ulterius lacerare non potest.

[January 17, 2009]

Here are the lower attachment fitting for the center flap tracks, ready to install. Photoshop provided the annual-report-style coloring; they are really just alodined aluminum, not nickel-plated unattainium. They are 3.5 inches wide; all the holes are 1/4-inch. They nest at the bottom of the flap cove, against the rear spar, with two bolts going through the spar into bathtub fittings inside the wing (which is an integral fuel tank), and four bolts threaded into the fittings through gusset plates embedded in the bottom skin. The skin sandwich is a little more than 1/4 inch thick, so the gusset and its bolts will disappear below the surface. The gusset is an elongated triangle, about six inches long, that will be bonded to the carbon-fiber inner skin of the sandwich along an internal rib.

A load of about 2,400 pounds (limit) is applied to the center lug by the fully-extended flap. It resolves itself into a 1,200-pound tensile component, which the gusset carries into the wing skin, and a 1,800-pound vertical component, reacted by a similar downward force from the upper fittings through a 1/4-inch-thick carbon-fiber reinforcing plate embedded in the rear spar. It is customary to apply a fitting factor of 2.0 for critical attachments like these (the standard factor of safety for most primary structure is 1.5), but these fittings are still more massive than is strictly necessary. It was necessary to provide sufficient material around the holes, and I wanted to be sure that the fittings would not distort to any significant degree under load.

I will install these on Monday and cut the shallow notches in the flap leading edges that will be required for clearance when the flaps are retracted.

[January 13, 2009]

Things are finally getting back to normal. I got the upper attachment fittings bolted and bonded into the wings yesterday. I hoped to get the bottom fittings ready to install today, but my mill vise seized up and I had to stop working to fix it. It was interesting to take it apart and see how it's made; there is a lot of inherited ingenuity hidden in these little everyday bits of mechanical engineering. The problem was a crushed ball in a thrust bearing; I removed the fragments and put the thing back together temporarily, while I locate a repacement bearing. I need to drill and tap four 1/4-28 holes in each fitting and make a tool that will enable me to locate the holes from underneath the wing when the fittings are in place. The next step will be to make the four links, two to a side, that go between the tracks and the bottom attachments. Once that is done, the remaining task, before the flaps can be used, is to add top and bottom surface gussets to distribute the center flap track forces into the wing skins. That sounds as if it should take a week, so it may be done by the end of February.

I have noticed, while taxiing with the flaps down, that they vibrate quite a bit, and I am somewhat concerned that they will produce a disconcerting clatter against the middle tracks, which are simply ramps designed to support an upward load only. The rollers may need to have tires. Tires -- that is, bits of hard rubber hose pushed onto an aluminum core -- might have another advantage, namely that of compensating for the misalignment between the rollers and the track surface. The track surface is parallel to the bottom of the wing, but the flap, because it is tapered, describes a sort of distorted cone as it extends, and so the roller as often as not rides on one edge of the track or the other rather than perfectly flush with its surface.

[December 27, 2008]

Having eaten and drunk sufficient over Christmas to make a little famine seem like a good thing, I finally got back to the airport yesterday and spent a couple of hours renewing my acquaintance with the airplane. I drilled the blind bolt holes in the bottom attachment for the left wing's center flap track, and, thanks to my generally virtuous life hitherto, they aligned properly with the ones in the wing.

I've been curious about whether I could begin testing the flaps at partial extension even before I get the surface gussets for the center tracks added. I ran a Cmarc analysis of the flaps in the takeoff position and found that the air load on each one is around 210 pounds, as opposed to about 360 pounds in the landing position. (The moment arm is also a couple of inches shorter.) It was interesting to see that with the flap in the takeoff position, at 1,200 in/sec (68 mph) the lift is 700 pounds greater than it would be at the same geometric angle of attack with flaps retracted; but only 420 pounds of this is applied to the flaps themselves. The rest is owing to increased circulation (that is, more upper-surface suction) caused by the flap, but acting on the wing.

[December 20, 2008]

My prediction (12/8) that I would finishing the various laminating tasks by the 19th was of course incorrect. They always are. The reason was partly that preparation for some of the tasks took longer than expected, and partly that Los Angeles has had a cold snap, at least by our standards, and between the early nightfall (the hangar has no lights to speak of) and the Arctic conditions (daytime temperatures in the low 50s) my working hours have been shortened and the cure cycle of epoxy has been lengthened. Unfortunately, I now won't get back to the airplane until the day after Christmas, because of various holiday activities. I spent most of yesterday's hangar time trying to determine where to drill the holes in the lower track attachment fittings to match, within a few thousandths of an inch, the existing holes in the rear spar. It's a matter of cutting and fitting without being able to see what you're doing, and of course you can't back-drill because the other side of the rear spar is the inside of a fuel tank.

[December 13, 2008]

My week of laminating began with splicing the tops and bottoms of the "canoe" fairings for the middle flap tracks. These are the same fairings as I used on the outboard tracks, and I had made up the half-shells some time ago. To join them, I fastened the top and bottom molds together, slipped the shells inside, and laid up a tape along the seam. This was a little tricky, since the tape is on the inside and I could barely get my hand in. I had to make a special vacuum bag that resembled a sock turned partially inside-out. The inner portion slid inside the shell; coaxing it into place provided a sensation similar, I imagine, to that of artificially inseminating a cow. Both fairings turned out nicely. Here one is before and after the splicing. In the picture on the right the two halves of the mold are lying beside the fairing; if you squint, the upper half looks like a spent Jovian thunderbolt or, as we call them today, a belemnite guard.

This will be the end result:

Next week I'll bond these fairings to the flaps, align the nose fairings and provide them with attachment flanges, and notch the leading edges of the flaps to clear the lower attachment fittings.

[December 8, 2008]

Yesterday I flew up to Palo Alto to attend a lecture on electric airplanes by Morton Grosser, a onetime associate of Paul MacCready. Leaving LA I encountered headwinds of 40 knots, and then found the San Joaquin Valley completely socked in with dense fog. I dropped down to 6,500 feet and bent my course westward in order to stay in sight of land while performing thought-experiments about how best to make a dead-stick landing in zero-zero conditions. The headwind slackened progressively as I flew northward, and I got to PAO in 2.1 hours. I was surprised to see at least two TwinStars parked there; maybe the airplane is a fave with Silicon Valley types. I like the airport, but I wish they'd put up a few more signs to help you get back to it. There's nothing on the 101, which goes right past it, to tell you it's there, and even if you know to take the Embarcadero/Oregon Expressway exit there's still no sign on the off ramp to tell you which branch to choose. And even if you manage to stumble on the one well-hidden sign in which the city has seen fit to invest, there are no further signs to help you get your bearings as you get closer to the airport. It's really ridiculous for a place that presumably attracts a certain number of out-of-towners.

I made the return trip in two segments, stopping for a few hours at Paso Robles. I observed 139 kias at 8.4 gph on the first leg, and the same indicated airspeed at 8.9 on the second. Both were at 11,500 feet, but the MP/RPM settings were a little different. Even the 8.4 reading fell short of what should be possible if my F is what I said it is a while ago -- 2.25 sq. ft; that's more like 2.4. There are various possible explanations, including instrument error, mixture setting (since fuel flow is a surrogate for power), and added drag from somethng like a sagging gear door. Since I have so much else to deal with now, I guess I won't find out the answer for a while. The wind had kicked up when I got back to Whiteman, and it was blowing 18 knots at 70 degrees to the runway. The tower instructed me to make left traffic for 30 -- an unusual maneuver -- so that I would be flying my base leg with a headwind rather than a tailwind. A good idea; I'd never thought of it. The approach was bumpy with lots of crab angle, but the landing was smooth -- demonstrating once again that greasers are chance events.

Last Friday I added air to the nosewheel strut, as I do every winter when the temperaures drop. I felt today that the strut was too full, but I noticed that the airplane seemed to track better during takeoff and landing. I don't understand why that would be, but I noticed how much of the nose strut of a Bonanza is exposed, and wondered whether I have been wrong to keep mine with only a couple of inches of piston showing.

[December 3, 2008]

Then along came Thanksgiving, with its interruption, sometime welcome and sometimes not, of the routine of airplane work. During the few hours that I spent at the hangar between then and now, I made another brief dip into the slough of stupidity, inadvertently installing (temporarily) the upper flap attachment brackets and then, observing the misalignment of several degrees in the resulting track position, shaved some material off the bottom of the corresponding lower bracket to match the error in the upper ones. It seemed incredible to me at the time that my extremely careful measurements had yielded such a grossly faulty result, but there it was. Or rather, as I finally discovered, there it wasn't, because once I had installed the correct fittings it turned out that the angles were nearly perfect, and now I had to re-machine the lower bracket to correct my first correction. Fortunately, small amounts of material were involved, and the part, which is still only roughly shaped, remains perfectly usable.

Before I begin actually installing the tracks, I have to do several laminations involving the fairings or "canoes" that will cover the tracks. Trying to be realistic about time for once, I wrote up a schedule, and found that these small operations, which don't sound like much work at all, will probably take seven days. I'm currently staying with friends in the mountains near Fresno, and am going up to Palo Alto next Monday and to Paso Robles on Tuesday; so I probably won't get the laminations done until around the 19th. Just in time for the next Holiday Hiatus. But I suppose there is still a fair chance that I will get the brackets and tracks (but not the surface gussets, which were really the point of this whole exercise) installed by the first of the year. I could then begin flight testing the flaps through the first half or so of their travel.

[November 25, 2008]

This seems to be the stupid season. It finally dawned on me a couple of days ago that the design of the bottom flap attachment fitting would be much simplified if I cut a notch into the leading edge of the flap rather than distort the fitting so as to preserve the flap profile. For a long time I have been thinking about this fitting and how best to make it, without its ever dawning on me that since this portion of the flap is inside a fairing anyway, it's not going to produce any lift to speak of and so the shape of its leading edge is of no consequence. I have now made all of the upper fittings, am nearly done with the first of the two lower ones, and have partially made one flap track. On the other hand, I haven't flown in a month. There must be something wrong with my priorities.

[November 16, 2008]

After cutting away some chunks of glass and foam, I was able to get at the fittings that I had stupidly buried, and to sponge up quite a lot of hydraulic fluid that had pooled in the dead space between the rear spar and the bottom skin. It appears -- I'm not absolutely certain yet -- that the leak was in fact in the line that I first suspected, showing that one can sometimes jump to a conclusion with no evidence and still be right. Good news for prosecutors. I was never able to figure out why the line leaked -- it continued to leak even after I tightened all the fittings mercilessly -- and so I made a new piece of line and used a different flare fitting, and the problem seemed to go away. I now have the upper track attachments fitted to both the left and right wings, and will start on the lower attachments next week.

[November 11, 2008]

I've noticed lately that the hydraulic system seemed to be losing fluid. Since I didn't see any big pools of the stuff on the floor -- either the airplane's or the hangar's -- I speculated that some interaction between the flaps, landing gear, and airbrake, all of which are hydraulically operated, was causing fluid to be dumped overboard from the reservoir. Yesterday, however, I found a pretty big pool of fluid on the left front corner of the airplane floor under the back seats. I put folded paper towels under the nearby connections, expecting to find the leak that way. Today there was no fluid on the towels but a new puddle in the corner. I then realized that the fluid was coming from a closed-off dead space between the bottom of the rear wing spar and the inside of the fuselage bottom skin sandwich. Six hydraulic lines related to the flaps pass through this cavity. Unfortunately -- this was very stupid -- there are connections inside the cavity, but the places where the lines enter and leave the cavity are potted with epoxy -- not so completely potted, however, that fluid could not find a way to leak out. Evidently, at least one connection was not tight. At first I jumped to the conclusion that the line nearest the leak was the responsible one, and I dug it out. I then discovered that there was quite a lot of hydraulic fluid inside the cavity, and I left it to drain overnight. As I was driving home I realized that there was no reason to think that the line alongside which the fluid was escaping from the cavity was the leaky one; it could have been any of the six, and the fluid could be flowing from one side of the airplane to the other before leaking out. The reason I had ill-advisedly potted all these connections into place was to isolate the wheel wells from the cabin; now I think I will have to open up a tunnel on each side so that the lines are accessible, and just pack it with Play-Doh or something to keep the wind from blowing in.

In the meantime, I've been fitting the middle flap track attachments to the left wing. This is fairly tricky, since the top fittings go into a very small and cluttered space, and they need to be drilled to match existing holes that I can't get at. So far, I've had pretty good luck. The underside of the track also needs to match the trajectory of the roller. I'm using a dummy track -- just the front end of a track -- to locate the front limit of the roller travel. Here's the dummy track in place in the left wing's flap cove, seen from below and above:

The tube is the aileron pushrod; it is supported by an idler every four feet. The two lines running under the top skin go to the outboard actuator; the lower line is for the pitot tube, which is located at the left wingtip. The clecos will be replaced by 1/4" bolts, and a gusset will spread compressive loads into the inner skin of the sandwich. Only the inner surface of the sandwich is stressed; it is made of carbon, while the outer skin is glass.

Here is the same dummy track lying on a drawing of the complete track. The track is not a slot; it is a ramp, and a single roller on the top of the flap travels along it.

I had a mechanical drawing class in high school, but I seem to have forgotten everything I learned about neatness and clarity. My drawings are all palimpsests -- masses of erasures, pentimenti, multiple views and even different objects occupying the same space on the page.

[November 7, 2008]

In the past couple of weeks I've received innumerable emails concerning the YouTube video that seems to show an exhibition acrobatic airplane losing its right wing in the course of a vertical snap roll, recovering in knife-edge flight, and rolling level just in time to land safely. Non-pilots, who in this case proved more sensible than their license-toting counterparts, generally wrote to ask whether this were really possible. Amazingly, however, a lot of pilots and engineers who should have known better accepted it as the real thing, even though it's pretty obvious -- particularly when the airplane touches down, bounces once, and immediately stops, just like a model -- that it's not. It seems that the tape is actually a clever piece of viral advertising for a clothing line. I'm not sure how you get to the clothing pitch; it must have something to do with an interview with the pilot to which you're supposed to find your way. Anyway, as far as the plausibility is concerned, and apart from the visibly inappropriate dynamics of the landing, I don't believe that any full-size airplane is sufficiently light and powerful to climb vertically on propeller thrust alone, as we see the airplane doing; and a vertical snap roll is a relatively low-stress maneuver that would not be likely to break a competition acrobatic airplane. In fact, it would probably not even bend a Cessna.

I spent the week making aluminum fittings for attaching the middle flap tracks to the wings.

[November 5, 2008]

The oranges are juicier today, the juice sweeter. Ex africa semper aliquid novi.

[November 4, 2008]

I mocked up the left middle flap track, using miscellaneous bits and pieces that I made years ago and then decided to discard. Surprisingly, it all fits together pretty well, although I had to re-route the pitot line around the flap attachment. I machined a sample upper attachment fitting out of maple; today I'll buy some 2024 plate and some new bandsaw blades and start making the real pieces.

First, however, to vote.

[October 22, 2008]

I did a short flight to test the behavior of the trim tab link, whose effect is to double the trim tab area. Nothing surprising. The trim authority at low speed was certainly not doubled, but I think that is because what limits it is not tab area but rather separation, and once the flow on the tab separates it doesn't matter that much whether you have one or two of them. This may turn out to be a problem when the flaps are down, but then again they may increase the downwash angle at the tail sufficiently to limit the amount of trim they require. I didn't test the nose-down trim authority with aft CG, but since that involves high speeds and small tab deflections, there is no separation issue and I'm pretty sure there will be no difficulty.

On the time-honored principle that one should always have two projects going at the same time, I am going to begin work on moving the aileron hinge lines aft to increase their aerodynamic balance and reduce the stick forces in roll, which have always been too high. I have hesitated over this project for a long time because of uncertainty about how best to contour the overhung nose of the aileron. An elliptical, well-streamlined nose makes a larger gap; the gap can be narrowed by making the nose of the aileron more blunt, but that leads to separation at large deflections, reducing the aileron authority. Hoerner reports a 20% increase in section drag due to an aileron slot; applied to 20 square feet of wing area, this represents an equivalent flat plate increment of 0.04 sq. ft. At 60% power, that represents .07 gph, or, at current prices, less than 40 cents an hour, so maybe I shouldn't be concerned. Hoerner does show that the drag increment can be almost entirely eliminated by thinning the airfoil section by 15% just ahead of the aileron. I could do that. There is also the option, seen on may sailplanes, of plastic gap seals that slide on the aileron surface like wipers and flex as the aileron nose rises above the wing surface -- another possibility.

[October 17, 2008]

The flaps now operate so routinely that the process of forgetting the past four weeks of fiddling with them is well underway.

I mentioned on October 10 that I was going to shorten the actuators, but a reader, Ken Phillips (of Cincinnati, I believe), suggested that it might be simpler and less pontincendiary just to add aluminum spacers sliding on the piston shafts to limit the actuator travel. I did so. The left cylinder now reaches its full extension just as the flap reaches its full retraction -- the inboard actuators are installed shaft-forward, so that they extend to retract the flap -- but the right one still wants to go a little too far. I'm going to shorten both piston shafts just a little, by 1/4 inch or less, so that the rod ends that screw into them are not bottomed. That way I'll have some adjustment available in case things move around with use, as they have a mysterious way of doing.

This matter of the travel limits of the inboard actuators involves two variables, the actuator travel and the location of the actuator anchor point on the airframe, relative to the retracted position of the flap. If I had planned things a little better I might not have had any problems, but one of the bad things about composite structures is that you can't drill out rivets or remove bolts and reposition anchor points. Once an anchor is drilled and bonded, there it is. It happens that I unwittingly placed my anchors in such a way that only by restricting the actuator travel to precisely the required amount, with the rod ends screwed all the way into the shafts, could I avoid applying hydraulic pressure to the stopped flap, with undesirable effect (see September 27 below). But then no further adjustment was available. No harm will be done by shortening the shafts a little, however, and that will allow fine-tuning of the retracted flap position.

To celebrate the apparent capitulation of the flap hydraulics, I started working on the linkage joining the two trim tabs, a simple job that I hoped to finish today, but didn't.

[October 13, 2008]

A visitor asked that I post a schematic of the flap hydraulics.

This sketch is simplified; it shows only one master/slave circuit, whereas there are four, and the single walking beam shown is really a bellcrank with five arms, four for the master cylinders and one for the "driver." See January 17, 2008 and January 8, 2005.

The only part that may be a little difficult to grasp is the equalizing function which is indicated in the detail on the left. A very small passage in the wall of the master cylinder allows fluid to pass from the pressure to the vent side when the piston is up against the flaps-retracted stop. As soon as the piston moves slightly (1-2 mm) on the extension cycle, this passage is blocked by the O-ring. The purpose of the passage is to allow the flap to retract fully even if some of the captive fluid has leaked out of the lines between the master cylinders and the flap actuators. The purpose of the single-acting "driver" cylinder is to drive the walking beam and the attached master cylinders to their limits.

[October 10, 2008]

The flaps seem to be working now without any significant leaks, but there is still a problem with the length of the inboard actuators. The best solution I see, since it is not practical to move the points where the actuators are attached to the fuselage, is to reduce the length of both cylinders by about 0.6 inch in order to ensure that they reach their end stops before the flaps do, or at least no later. (This was the cause of the bent shaft I described on September 27. I thought I had fixed the problem, but I was wrong.) I should be able to get that taken care of on Monday. The one synchronizer cylinder that was leaking is now sealed. A small scar from the lathe chuck happened to fall right under an O-ring; it was easily removed with emery paper.

It will be a relief to work, for a change, on some system that does not involve hydraulic fluid.

My statement in the previous entry that all-flying tails automatically compensate for changes in the wing downwash angle was false. I was not thinking clearly when I wrote that. It must be that the immediate, transitory pitching effect of a flap is mainly influenced by the position of the horizontal tail with respect to the wing wake. The long-term effect of putting flaps down, however, is always a more nose-down pitch attitude, if speed is unchanged.

[October 5, 2008]

A longtime correspondent, Dan Fritz, challenged my opinion that deploying flaps would make the airplane pitch down. After reflecting on it, I think he's right: more likely, it will pitch up. What had made me think it would pitch down was my experience with Melmoth 1, and also with my friend Russ Hardwick's Cherokee Arrow, which I flew quite a bit while I was between Melmoths. But both of those airplanes had stabilators, which automatically compensate <<Author's note: This statement is incorrect; see above.>> for the change in effective decalage (the difference in incidence between the wing and the horizontal tail) that the flaps produce. Melmoth 2 has a fixed stabilizer, and it will almost certainly respond to a change in decalage by initially pitching up. Of course, to maintain speed it will ultimately have to settle into a new attitude with the nose lower than before; but it will be necessary to add nose-down trim to get it there.

I spent several hours today wrestling with leaks in both ends of the left outboard flap actuator. It was looking pretty good when I left the hangar, but I'm still not certain that it's fixed.

[October 3, 2008]

I believe that the struggle between me and the flap hydraulics is finally tilting in my favor. The right flap now behaves properly, and the inboard end of the left one keeps pace with it. The outboard end of the left flap is not cooperating, but it has an evident leak, and I have come to suspect that leaks, not trapped air bubbles, were responsible for the initially crazy behavior of the system. I have been gradually eliminating minor leaks all week, and it was after I fixed a pretty significant one -- due to a damaged O-ring -- in the right inboard actuator that the right flap suddenly began working properly. I suspect that fixing the drip in the left outboard actuator will have a similar effect there. Surprisingly, the only cylinder that was completely leak-free from the outset was the one whose shaft got bent and had to be straightened. No doubt there is a moral in that, somewhere.

By luck -- I did not have much leeway in the sizing of the actuating cylinders -- the flap speed appears to be about what you'd want: not exasperatingly slow, but slow enough to allow the pilot to make trim adjustments and to stop the flap if something asymmetrical begins to happen. I am curious to see how the flaps and the airbrake interact -- operationally, that is, not aerodynamically. The airbrake produces a strong pitch up, whereas I believe that the flaps will cause the airplane to pitch down. I imagine that the landing sequence will be to open the airbrake in order to slow the airplane to gear speed (100 knots), then lower the gear, then extend the flap to the takeoff setting, which involves about 10 inches of aft travel and a wing area increase of about 16 square feet, but almost no angular deflection of the flap. Landing flap -- 30 degrees deflection -- would be used only for the final portion of the approach. I hope for a reduction in approach speed (at, say, 2,000 pounds) from 85 to 75 knots. It will be some time before the flaps can be used in flight, however, because I still have to make and install the center flap tracks, which will bear about half of the total flap load.

[September 27, 2008]

This was an exciting week, at least on the scale of what goes on in my hangar. After cycling the synchronizer cylinders alone last week, I installed the actuator cylinders and plumbed them. The inboard ones, which are inside the fuselage and readily accessible, were easy, but the outboard ones are crammed into a small cove in the trailing edge of the wing along with a lot of other stuff like aileron actuators, and I had to learn a particular installation sequence in order to get them in at all. Here's what the little cove looks like with the cylinders and their plumbing in place; for scale, the piston (the slender steel cylinder at right) is 3/8" in diameter.

The pushrod running across the upper half of the picture is 3/4" in diameter and actuates the left aileron. The curvy aluminum thing at right is the outboard flap track. The coiled up wires near the center of the picture are for the outboard fuel quantity indicator, which is not yet in service. The flap actuating cylinder is mounted in a yoke; the cylinder itself is not clearly visible, but it resides in a tunnel in the fuel tank.

With the actuator in place, I more or less charged the lines between the synchronizer cylinders and the actuator with fluid, and tried running the system. The first thing I found out was that I had crossed the lines going to the right outboard actuator, and it was trying to retract the flap while the other three actuators were extending. I fixed that. The flap then operated, albeit haltingly and unevenly, an indication that I had not successfully bled the system. Then disaster struck. After fully retracting the flap, I discovered that the piston shaft of the left inboard actuator was bent like a pretzel. Well, maybe not a pretzel, but at least some non-straight thing. Viz, after removal:

It didn't take long to understand what had happened. Either I once figured this out and then forgot about it, or I never figured it out at all, but the inboard actuators, which are extremely long and slender and are installed backwards, so that they pull the flap down and push it up, have to be adjusted so that they reach their internal stop before the flap reaches its up stop; otherwise the full system pressure is applied to the extremely skinny actuator, and it buckles. At first I wasn't sure I would even be able to get the actuator out of the plane, because they have to be at least partially retracted in order to be removed; but I was able to partially retract the piston despite its elegant hyperbolic arc, and it did come out fairly easily. More surprisingly, I was also able to straighten the piston. My time ran out on Friday before I had a chance to test it again; maybe on Monday I will finally emerge from these woods. Then I can start cleaning up; the airplane and hangar are littered with hydraulic-fluid-soaked paper towels, and look like one of those scenes in ER when the patient is bleeding out.

[September 19, 2008]

Today marked some sort of milestone. I began to bleed the flap hydraulics by running fluid through them from the pump. In order to do this I first re-plumbed the system, bypassing the flap actuator lines, so that the synchronizer module was connected directly to the hydraulic pumpand reservoir. At first nothing happened. Then I became aware that because the lines were more or less empty, the pump was sending fluid from the reservoir to the synchronizers, but returning mostly air to the reservoir. I kept replenishing the reservoir, and gradually got more and more action out of the synchronizers. I also began to discover leaks, however -- that was expected -- and so I didn't completed the bleeding; I'll continue with it on Monday.

Like the gear and airbrake circuits, the flap circuit uses a two-way valve with a closed center. To actuate any of these services, you hold the handle up or down until the action is completed, and then return it to the center. The hydraulic pump runs whenever the handle is not in the center detent. (Actually, there is one exception: the motor does not run when the airbrake handle is moved to the "retract" position; springs retract the brake.) Closed-center valves are necessary because open-center valves would let hydraulic fluid flow freely throughout the system, and no pressure would ever develop. But they are also necessary to hold the flaps and airbrake in any extended position. The landing gear has overcenter up and down locks, but the closed-center valve, which traps fluid in the lines, also provides a backup to the downlocks which proved useful on one occasion (January 28, 2005). I have become aware, however, that hydraulic fluid expands considerably when heated -- 3% increase in volume between 60 and 140 deg F -- and that when the flaps are finally working I should not park in the sun for long periods with the flap fully extended. It is only when the flaps are extended that there is no way for the system to take up the expansion due to heating.

[September 17, 2008]

For the first time, I changed the oil wthout getting the engine hot first. The reason for hot oil changes is, I suppose, to thin the oil and speed its draining. Instead, I removed the plug on Friday and let the engine drain over the weekend. I suppose that one could argue that since running the engine before an oil change gets a lot of the oil up into the passages in the engine, from which it takes a while to drain down, and also spreads it over the engine's internal surfaces, a cold oil change has the advantage of having already allowed some of the oil "up in the engine" to find its way back to the sump. In any case, it was the cleanest oil change I've ever done, because it was so easy to remove the plug without having to avoid all that hot metal. I didn't spill a drop.

After examining the cabin air inlets, I'm puzzled about how water got into the back seat area. I don't see how it could have gotten in through the air inlet, but I can't see any other source for it either. The front is a different story; it's obvious that water could come in there, and would immediately leak down to the floor. I need, at the very least, to make a plug for that inlet. I pulled the rear seat carpets, which had had baggage piled on them for days while they were wet, and laundered them. Most of the mildew smell went away. I was disappointed to find, however, that the Velcro that held the carpet in place had a much greater affinity for itself than for either the floor or the carpet. I need to find a really bulletproof adhesive to stick the Velcro to the floor, and should probably get an upholstery shop to sew the other half of the Velcro to the carpets.

I hope now, with no more travel planned for the forseeable future, to finally get the flaps working.

[September 12, 2008]

We got back yesterday at about noon after spending three days -- parts of four days, actually -- crossing the country. The unexpectedly long return included many hours spent in FBOs' lounges waiting for clouds to lift. I had promised Nancy that we would conduct this entire trip VFR -- several unnerving experiences in Melmoth 1 apparently made her phobic about IFR flying -- and this proved to be a troublesome commitment, although necessary, since without it she would not have consented to make the trip at all. I suppose this no-IFR rule is my belated punishment for the bold go/no go decisions of my youth. She finally did consent to what turned out to be a five-minute climb through clouds to VFR on top when confronted with the threat of being weathered in for four days in Bartlesville, Oklahoma.

I learned on this trip that there are some liberals in Indiana, and that inner America is a culinary disaster area. The plane performed well, with no mechanical problems and cruising speeds in the 160-170 ktas range on an average of 8.4 gph. Despite the engine's habit of oozing oil from many pores, the result of its having been stored for 20 years while I built the plane, it actually consumed comparatively little oil -- a quart every ten hours or so. You don't fly a homebuilt for 37 hours without discovering some problem, however, and I discovered after a few downpours -- while the airplane was parked, not flying -- that rainwater gets into the cabin, apparently through the NACA inlets on the right side and the hinge line at the top of the baggage door. The carpets got soaked at Taunton, and we never had a chance to dry them out before piling tons of luggage on them. They now have a mildewy smell.

[August 27, 2008]

After we collected our daughter from Williamstown, where she had spent the summer as an acting apprentice at the theater festival, we had an unbelievable amount of baggage to contend with. It barely fit in Dave Noland's SUV -- crossover, actually -- and just about filled M2, behind the front seats, to eye level. The thing next to my right foot is a bathroom scale that I brought along from LA, anticipating something like this. Actually, the stuff added up to less than 250 pounds, so the weight was not a problem so much as the bulk. Lily remained in New York, so at least we didn't have to shoehorn her in along with everything else. We landed at Taunton, MA, an airport with the most paranoid and inconvenient security arrangements I've ever seen, and, apart from a sightseeing trip out along Cape Cod, M2 will remain there until we return to California in a couple of weeks.

I used to skydive at Taunton when I was in college, and once came within five seconds of augering in when I somehow failed to locate the D-ring on my ripcord. I landed off the airport in a clearing among trees in somebody's yard, feeling like one of those soldiers who hoped that the Normandy farmyard into which they descended did not belong to a flintlock-toting pétainiste.

[August 17, 2008]

Not surprisingly, we left later on Wednesday than we had planned. We stopped for the night at Gallup instead of somewhere in Kansas, flew to eastern Indiana the next day, and arrived at Orange County (Montgomery, NY) at noon on Friday. Block performance did not match the spot numbers observed during local flights. In theory the plane gets 21 nmpg at 170 knots. In theory, you pick up an average 10 knots or so eastbound from the prevailing wind. But throw in a wind that perversely blew much of the time from the northeast and convective activity that had us at 2,000 agl a lot of the time, and we averaged 145 knots and 17.4 npmg. But the midwest is quite a bit more interesting from 2,000 feet than from 12,000, and the time passed quickly. Used one quart of oil and something like 127 gallons of fuel. The only thing, besides the wind, that didn't work perfectly was my David Clark headset, which began soaking my neck with silicone breast-implant goo somewhere in Nebraska.

[August 11, 2008]

We're leaving Wednesday for the east coast, and so today I was giving the plane a once-over that included draining the sumps. This is something I seldom do, because in almost six years I have never found any water or anything else in them, and the quick-drains have tiny O-rings that drip when little bits of dirt get stuck under them. Sure enough, the left one started to drip after I drained the sump -- nothing in it, as usual. Normally I can get it to stop dripping by letting a rapid stream of fuel flow through it -- I collect the precious stuff in a jar and pour it back into the tank -- but this time that didn't work, and so I had to remove the drain assembly from the airplane to clean the O-ring. This is a difficult and messy job that inevitably includes spilling a pint or so of fuel on the ground by way of my armpits. Eventually I got the drain out, however, and cleaned it. In the duct above it I discovered a little mass of trapped tank scum. On close examination it proved to include quite a variety of mysterious substances and, tragically, the corpses of several ants. Viz:

[August 9, 2008]

I was at Santa Rosa, north of San Francisco, yesterday and Thursday, being a judge in a contest run by the CAFE foundation as a part of a multi-year NASA-sponsored effort to improve the technology of general aviation airplanes. NASA is offering substantial cash prizes for the achievement of various goals. The ultimate target is a PAV -- personal aerial vehicle -- that is quiet, efficient, and capable of largely autonomous flight, including automatic navigation and landing. Originally this year's field was to consist of five competitors, but only three ended up participating: a Slovenian-born Pipistrel Virus (34-foot span version), an Urban Air Lambada, and a Flight Design CT, both of the latter built in the Czech Republic. All three are two-seat LSAs with Rotax engines, although the Virus had forfeited its LSA status by installing a variable-pitch propeller. The Lambada is a motorglider with a long, complicated wing; the Virus and CT are polliwog-shaped high-wing designs. The Virus is the more gracile of the two. The Lambada is an old-fashioned airplane, well-behaved in flight and gadget-free. It has the most unmistakeable aerodynamic buffet prior to the stall that I have ever seen; the entire airplane shakes violently, and the engine jumps up and down visibly in its mounts. The Pipistrel is loaded with high-tech equipment, including various electronic displays and an autopilot with altitude hold. It has camber-changing flaps and sailplane-type airbrakes, and a correspondingly varied set of cockpit controls. The CT is most like a conventional small trainer, with the expected controls and round instruments in the expected places. In the picture below, the airplanes (not counting the deceased Douglas in the background) are, left to right, the CT, the Pipistrel, and the Lambada, whose outer wing panels have been removed. The Lambada, which was still involved in some inflight data collection when the photo was taken, is carrying two temporary CAFE pitot-static booms under its wings.

I found the CT to be the least pleasant of the three in flight. I was surprised, in fact, that an airplane with its handling qualities could even come to market. It is directionally unstable; if you floor a rudder pedal the ball goes over the the edge of the inclinometer and just stays there; if you roll without rudder the effect is the same. I thought those flying qualities went out with the Fokker Triplane. It was also much slower, both climbing and cruising, than the Virus, which achieved a top speed of 163 mph in last year's competition; the CT's owner blamed its lethargy on an unhappy choice of a propeller for this contest.

[Note added December 20, 2008. It has come to my attention that I was wrong to say that the CT is directionally unstable. It is stable, since when disturbed by a rudder or aileron pulse it comes to rest flying somewhat sideways, and does not diverge from that position. I should have said that its handling suffers from a lack of directional centering, or, more broadly, that of more than 200 types in my logbooks since 1961, it has some of the most unpleasant handlng qualities I have encountered, combined with entirely lackluster performance. This may not be true of all CTs, however; I gather that there have been some changes from the factory.]

I had a long conversation with Pipistrel's 24-year-old chief designer, who expounded some aerodynamic concepts I had never heard of. It struck me that in different cultures, different ideas are taken for granted, so that, for instance, all sorts of physical disorders are attributed in France to the liver, an organ that goes almost unnoticed in the US, except among drunks.

[August 2, 2008]

I completed the neutral-point hunt yesterday with a flight with 200 pounds of ballast, CG at 40%. The flight was unremarkable and the resulting data set fell nicely into line with previous ones. The stick-fixed NP is evidently at FS130, which is 60% of MAC, just as DWT said. I am setting the aft limit of the CG envelope at FS125, or 45% of MAC. I did discover that there is insufficient trim authority for fast cruise with aft CG. I am currently using only one of two trim tabs, and I expect that hooking up the other one will solve this problem.

[August 1, 2008]

On Tuesday I added another 50 pounds of ballast and did another stick force sweep, which confirmed the neutral point location finding from the first two. I plan to do one more today, with the CG at 40%. This is equivalent to four 170-pound occupants, 40 gallons of fuel and 50 pounds of baggage, and is the design aft limit. It provides a 7-inch static margin, which is pretty ample. In order to go farther aft, I would need to get more sand.

During Tuesday's flight the angle of attack indicator hung in the middle of the gauge. It turned out that the plastic face plate under the needle had cracked and sprung out sufficiently to interfere with the needle. I made a new face plate out of aluminum. It is somewhat crudely painted -- I never have the patience to do things like that well -- but it will serve. A remarkable thing was that when I called Safe Flight, the New York manufacturer of the device, to get some guidance about dismantling it, I talked with Joe Inserro, the same person I talked with when I first got the instrument 35 years ago.

[July 28, 2008]

I was looking through some old documents relating to the design of Melmoth 2 and I was surprised to find that some very early estimates of weight and drag were not too far from the truth. For example, a 1983 weight buildup arrived at an empty weight of 1,375 pounds. The actual weight at the first flight was 1,397. Since then quite a bit has been added, so I don't know how self-congratulatory I should be about the first estimate, but an undated, handwritten document that I think also dates from the 1980s has "Assuming We [ie empty weight] = 1600 lbs," which is not too far from the present value of 1,585. I also did a drag breakdown (handwritten, undated) that came up with an F of 2.5 square feet, which was almost exactly right if you made (as I did) the most pessimistic assumptions about laminar flow on the wings. The current estimate is about 2.3 sq ft.

A dot-matrix printout from an old longitudinal stability program I wrote puts the power-off neutral point at FS 124.11. That seems too far forward; Digital Wind Tunnel puts it at 129.97 or about .60 mac. Today I did a couple of flights to measure static longitudinal stability as a function of CG location. I first flew with a forward CG (113.43; .25 mac is 117.86, and mac is 35.26). I then loaded 100 pounds of sand (in bags) into the baggage compartment, which moved the CG to 118.40. (Actually, I added 10 gallons of fuel as well, but that has a relatively small effect on the CG location.) On both flights, I trimmed for 120 knots, then, without retrimming, accelerated to 160 and then slowed to 90, recording the stick forces required to maintain speeds at intervals of 10 or 20 knots. On the ground, I plotted the results and eyeballed a straight line through each series. Now, in principle I am measuring pounds of stick force per knot, but not having calibrated the Futek I'm just calling it millivolts (mV) per knot. The forward CG line has a slope of .27 mV/knot; the more aft one .19. I just about gasped when I extrapolated to the CG location at which the stick force slope would be zero, that is, the neutral point: 130.2. Given the many approximations involved in the test, that result is for all practical purposes identical to the one computed by Digital Wind Tunnel. It was interesting to see that although the airplane was obviously less stable with the ballast, it didn't feel subjectively worse; it still had good speed stability on final approach and felt normal throughout the speed range. Tomorrow I will add another 50 pounds and repeat the test.

[July 25, 2008]

I intended to make the first flight test with the stick force sensor, which I installed yesterday. But I got involved in plumbing the bubble catcher, and used up all my time on that. Here's the stick force thing:

I had to make the L-shaped adaptor between the bullet-shaped sensor, hereinafter "the Futek," and the sidestick mount. The red and blue wires coming out of it are for a press-to-talk switch. The two shielded conductors coming out of the Futek carry both the incoming excitation voltage, which I'm taking from the airplane's 12-volt bus (the airplane electrical system is 28 volt, but the Futek is limited to a maximum of 20 volts), and the output voltages, which are on the order of a few millivolts. One group is for the lateral axis, the other for the longitudinal. I tested it by lifting the weight of the elevator with the stick; it registered around 8 mv, and was quite well damped, so I think it should be possible to get good readings in flight. I have it hooked up to a $15 digital voltmeter that reads in increments of .1 mv, and I'm looking at the X axis, that is, pitch, only. Javier Arango, who will be the ultimate user of all this stuff, is ordering a data logger that will store continuous stick force information in two axes, as well as about ten other channels of data which we have yet to dream up (stick position would be an obvious candidate). Flight path and three-axis rate and acceleration information will be recorded by the Appareo gadget.

Today's progress, such as it was, consisted of beginning to connect the lines between the synchronizer, the bubble catcher, and the hydraulic actuators for the flaps:

What you're seeing is the compartment beneath the back seats. The front of the airplane is to the left. The floor panels and the seats are supported by four carbon-fiber rails. Each aft-facing rear seat is located by several pins and locked down by a single bolt. The aluminum door in the middle of the floor will eventually have the oxygen outlets under it. The structure along the left side of the picture is the rear spar and main landing gear well; on the right edge are the tracks for the retractable boarding steps. About a third of the synchronizer plumbing is in place.

[July 17, 2008]

We got back from Cape Cod last night at midnight.

I flew a bit today, and thought a bit about what I need to do between now and a month from now when, if all goes according to plan, we will return to Cape Cod, this time in Melmoth 2. One big item is the leak in the right wing tank, which will require removing the wing. That's not a particularly difficult job, or at least it shouldn't be -- it's been on and off many times -- but I don't exactly look forward to doing it. It will pay some dividends, however, such as an opportunity to weigh a wing in its more or less completed form. That in turn will tell me the weight of the fuselage, and allow me to recalculate the actual factor of safety of the wings. It was 10 (ultimate) with two aboard when I designed the plane, but I underestimated the fuselage weight then. The reason for wanting to fix the wing tank leak now, rather than continue to let it go, is that it is located fairly high up in the tank and isn't a problem when there is less than 25 gallons (that is, 50 total) in it. That's fine for local flying, but for a cross-country trip I like to be able to carry 60 or 70 gallons (the total capacity is 142).

Another thing I want to get out of the way is the experimental determination of the neutral point. I described the procedure on June 14. Knowing the neutral point would help to determine the weight limit for rear seat passengers, among other things.

[June 18, 2008]

I finally got the bubble catchers assembled. Temperatures at the airport are forecast to be in the 97-109 range tomorrow and the next day, so I may not get this installed. Still in shock over the Lakers' total capitulation to the Celtics, I am going to Cape Cod to recuperate for three weeks -- plus my son is getting married there on July 12 -- and won't get the flaps moving on their own power until the latter part of July. Here's what the bubble machine looks like. Each tower is an inch in diameter and four inches tall.

[June 14, 2008]

As part of Javier Arango's project of collecting flight test data on his WWI airplanes, I ran some tests in my airplane with an Appareo GAU1000 flight data recorder which Javier had acquired. This is a little self-contained gadget about the size of a Rubik's cube. It costs $2,000, and performs what would have been considered miracles a decade or two ago, but are now merely routine digital tricks. Using GPS and solid-state gyros and accelerometers, it records location, speed, altitude, acceleration in three axes, pitch and roll rate, and so on. Display software allows you to replay your flight, a la Flight Simulator, but I find that aspect less interesting than the ability to measure a lot of variables like pitch attitude, roll rate, takeoff acceleration, and so on. One puzzling thing, however, is that the reported rates of climb are on the low side, not just in terms of my expectations but also in terms of the altitude changes and times recorded by the instrument itself. I suspect a programming error, but I have e-mailed the manufacturer to try to clear this up. The sevice samples its various parameters ten times a second, then smoothes and stores them at quarter-second intervals. Data can be downloded to Excel for futher manipulation. I expect to have a lot of fun with this (until Javier takes it back).

Another gadget Javier got, and which I am going to test first, is a stick force gauge. You can locate the neutral point with this thing by observing the stick force necessary to hold a speed 20 knots, say, below the trimmed speed, and then putting a couple of hundred pounds of sandbags in the baggage compartment and repeating the experiment. With an aft CG the stick force will be less, and a straight-line extrapolation through these two values to a stick force of zero gives you the CG location for zero longitudinal stability. Of course the thing that really matters is pilot comfort, and so the decision about how far forward of that point to put the aft limit of the CG range is a subjective one; but it will be interesting to compare the measured value with the one calculated by Digital Wind Tunnel. Likewise the phugoid period, which can be conveniently measured by the Appareo.

On Friday I picked up the bubble catchers from Flyte-Weld, and will start installing them on Monday, by which time I expect to have recovered from the depression and paralysis brought on by the collapse of the Lakers on Thursday.

[June 4, 2008]

Nancy and I went away for a week to stay with friends near Fort Bragg, on the Northern California coast. Their house overlooks the ocean and a rare (for the area) sandy beach, and we spent hours each day playing "beach boccie," which is a ballistic form of boccie ranging over both dry sand and smooth, wet -- but deceivingly undulant -- tidal flats. It was a lovely time, marred only by our having to drive ten hours each way because Los Angeles chose the day of our departure to undergo a freakish weather phenomenon preclusive of flight (at least for Nancy and me). It was interesting however, that the seats of my 12-year-old Geo Prizm were fidget-free for both long drives. I'm using those seats as models for my pilot's seat, but probably in vain because what matters is no doubt the depth and elasticity in a seat, not just its superficial shape, and those I cannot duplicate.

Today I finished making the parts for the bubble-catchers and took them down to Flyte-Weld, the welder near Burbank Airport whose work I was so pleased with a couple of years ago when I started this seemingly endless flap-actuation project. Chris Mogenson, the Hephaestos of this sooty forge, said he'd do the welding himself -- it's really a job shop whose welders do things by the hundreds, not four at a time -- but that it wouldn't be ready til late next week. I guess I need to find something else to occupy me in the meantime.

I've been having a hard time with the nylon tubing and fittings that I'm using. The description in the Aircraft Spruce catalog of how to assemble the stuff is pretty sketchy. To complicate matters, the 1/8-inch NPT threads on the nylon fittings are smaller than AN standard -- that is, they correspond to a portion of the tapered tap closer to its tip -- and they are really too small for a snug fit in holes that were tapped for AN pipe threads. Conversely, if you size a hole for the nylon fittings, you can't even start an AN fitting in it. I don't know whether an assembly lubricant should be used on the hose connections, or whether a thread sealing material, like teflon tape, or compound, like Tite-Seal, would be appropriate for the pipe threads. I have found nothing online. Of course, I'll figure it out eventually for myself, like most other things; but it's annoying to be so ignorant about such a commonplace product.

[May 20, 2008]

After trying to fill the synchronizer cylinders and lines without introducing any bubbles, I finally concluded that I need a bleeder in each of the four lines from the master cylinders to the actuators. Filling them is just too difficult and uncertain otherwise. These bleeders are actually air traps: vertical cylinders about 4 inches tall with a pressure-tight cap on the top. They're something like an inverted gascolator. Fluid enters and leaves at the bottom, but remains in the cylinder long enough for bubbles to collect at the top. I had one of these in Melmoth 1 and it worked fine. But this will delay the operation of the flaps for another couple of weeks, because I'm going to be away the week of May 23-30. Actually, even when the flap are operating they won't be working, because until I add the middle tracks they can't be used in flight.

[May 10, 2008]

The electrical connections for the flap are done. They were very simple, but some head-scratching was required to figure out how the flap and airbrake were wired, since I did not have a wiring dirgram for them. (Much of the plane has been built impromptu, without drawings, and although I always tell myself how important it is to document everything, I seldom get around to doing so.) I spent a while trying to puzzle out whether I had the flap valve rotating the right way; there was a 50-50 chance that I had it backward, and that the flap would go up when the handle went down. That would be easy to correct by simply swapping the cables at their connection points, but as far as I can tell from comparing the flap valve to the gear valve, I happened to get it right the first time.

I have worried quite a bit about the difficulty of bleeding the lines between the synchronizer and the flap actuators, but it occurred to me this morning that it is actually easy to purge air from the cylinders themselves, and the only bubbles that would be likely to be present would be in the lines. Since the internal cross-section of the smallest cylinder is some 30 times larger than that of the line, and since air does not compress to zero volume, even a four-inch-long void in a line would produce a shift of less than 1/8 of an inch in the position of the flap.

[May 7, 2008]

I had my first hydraulic flood today. The first of many, I'm sure. I was installing the flap actuating handle, and in the course of setting it up I cycled the flap control valve several times. The hydraulic pump wasn't running, but fluid ran from the reservoir to an open connection under the back seats, where the synchronizer is. By the time I noticed what had happened, the reservoir was practically empty, but the well under the seats wasn't.

The flap handle is now in place and working, except for the electrical connection, which I will do tomorrow. Like the gear and airbrake handles, the flap handle rotates a pulley which drives a two-way, center-closed valve, located under the passenger's seat, by means of a cable loop and a second pulley on the valve stem. The cable, which is about eight feet long, runs through flexible conduits. Those for the gear and airbrake are teflon-lined bicycle-brake cable housings; for the flaps I tried 3/16" nylon tubing, which is lighter and seems to work equally well. On the handle there is a cam that actuates the hydraulic pump by means of a single microswitch. The normal position of the handle is centered; to raise or lower the flaps, gear or brake you move the appropriate handle in the appropriate direction and hold it until the action is completed -- a matter of four or five seconds for the landing gear. You then return the handle to the central, valve-closed position. The hydraulic pump runs whenever the handle is out of center. I used this system because the more conventional one in Melmoth 1, which was also hydraulic but with electric rather than manual control, required a bunch of solenoid valves and microswitches and and quite a lot of plumbing and wiring. This one has no solenoid valves, three microswitches, and little plumbing or wiring.

The pictures below give some idea of how the system looks. The first one, below left, shows the flap handle mechanism not yet installed. The pulley, handle, and microswitch are visible, as are the cable, its nylon housings, and the barrel-and-set screw thing that keeps the cable from slipping on the pulley. The next picture shows the handle in place in the panel; the NACA 4415-shaped grip is removable so that the handle can pass through the slot. When it is in its center, neutral position, the handle rests in a detent. The handle, which slides in and out about 1/4-inch with respect to the pulley, is spring-loaded forward and must be pulled slightly aft to clear the detent before being raised or lowered.

The last picture shows the other end of the cable loop. This is the hydraulic jungle under the right front seat (it is also visible, viewed from below, in the entry for January 31, 2007). The gray thing, lower left, is the hydraulic pump, which came from a T-33. The flap valve is the thing with the large, thin hexagonal nut holding it to a green aluminum mount. The cable and its barrel lock are just visible to the left of the check valve with the stamped assembly date of 1966. I hope I can remain functional for as long.

[April 30, 2008]

Last week I got 15 feet of high pressure nylon tubing from Aircraft Spruce, but it turned out that I needed 16 feet. While waiting for the additional tubing to arrive, I took the partially-built flap handle out of the panel in order to complete it. The first problem was to figure out what I had had in mind when I made it, some time back in the 1980s. It gradually became apparent that there was supposed to be a limit sensor that would shut off the hydraulic pump when the flap was fully retracted. This is a feature that the other hydraulic services on the airplane -- landing gear retraction and air brake -- do not have. You just hold the handle in the up or down position until the cycle is complete -- you can tell by a change in the sound of the hydraulic pump -- and then restore it to its neutral center position. When I originally built this thing I didn't anticipate the self-bleeding feature of the hydraulic synchronizer, which requires that the pump continue to run briefly even after the flaps reach their fully retracted position. So I discarded some ingenious-looking little levers and springs and was able to carve away some portions of the handle structure -- saving, I'm sure, a number of grams -- and added a cam and microswitch to turn the motor on at any time the flap handle is not in the neutral position.

During periods of mental idleness I've been trying to figure out how best to fill all the flap-related lines and cylinders with hydraulic fluid without admitting too many bubbles and also without making a huge mess. It's not going to be easy.

[April 16, 2008]

Having fixed the leaky cylinder -- a pipe-thread problem, as usual, solvable with Tite-Seal -- and hooked up the correct end of one actuating cylinder to a master, I confirmed that the travel ratio was precisely what I had calculated that it should be -- not surprisingly, the value of pi having been known with sufficient precision since at least the time of Archimedes. Next, I had to make internal stops to limit the travel of the master cylinders. I machined these today, and the cylinder travels are now within .003 or less of the intended values. So far, so good. Tomorrow I will epoxy the stops into the cylinders, reassemble them once and for all, and install them in the frame.

I had occasion to look at some old photographs of tuft tests of Melmoth 1's double-slotted flap. The quality of the flow attachment was astonishingly good. Here is a shot, taken some time in the 1970's with a camera mounted on the tail, just as I was about to touch down -- in other words, at close to the maximum lift coefficient.

[April 14, 2008]

Today for the first time I connected one of the master cylinders to some of the flap actuation cylinders (the purpose of the master-slave arrangement is to synchronize the four actuating cylinders). Hydraulic fluid is messy at first, like a baby. I found that one actuator cylinder leaked; I sprayed fluid all over the place when a hose connection that I hadn't sufficiently tightened popped off; and I attached the wrong side of the inboard actuator to the master cylinder -- I didn't realize this til I was driving home -- and so the travel measurements I took didn't mean anything. Tomorrow I'll repeat today's experiments, I hope with better results and less splatter.

[March 31, 2008]

I have been derelict. Our son and his fiancee visited from New York, Easter came and went, and there were various household and work duties to discharge -- in short, I have not progressed much. But I have at least installed a good deal of the under-floor plumbing for the flaps. For the first couple of days that I worked on that, I made no progress at all; mostly I just sat in the back of the plane staring at the empty space, shifting the synchronizer and the not-yet-installed oxygen bottle around to see how they would best fit, and trying to decide how to route tubing and locate connections so as to ensure accessibility and minimize the number of expensive fittings needed. It's somewhat like a jigsaw puzzle -- slow at first, but gradually gaining speed as more and more pieces fall into place.

Yesterday I had an e-mail exchange with George Braly of GAMI (the manufacturer of, among other things, injectors whose orifice diameters are tuned to each cylinder in order to ensure even mixture distribution) about the specific fuel consumption of my engine. The question arose because I was asked to repeat some of the windmilling glide tests I did a while ago and wrote about in Flying, and in order to draw conclusions from these tests it is necessary to know two basic parameters that govern the drag of the airplane. One is CDo, the parasite drag coefficient, and the other is e, the span efficiency factor, which is a correction applied to the geometric aspect ratio in calculating induced drag. I obtain e, which is 0.86, from computer analysis using Cmarc; CDo, which is harder to ascertain, comes from comparing measured performance with calculated performance. Performance calculations involve two semi-unknowns, propeller efficiency and specific fuel consumption. My performance calculation program, in Loftsman, uses mathematical models to approximate these parameters, which vary with speed, power, and various other conditions. I had obtained performance charts for my Hartzell propeller which indicated that its efficiency was higher than I thought -- I had assumed a peak of .86, but Hartzell claimed .89 -- and the question now was whether I could pin down sfc with equal precision (and credibility). The program was saying .44 to .45 lb/hp-hr at 55% power, and Braly thought that .44 was a plausible number. But in the course of the discussion he mentioned that the EGT at which best sfc is achieved gets closer to peak as power diminishes. In other words, one should run 75 degrees Fahrenheit LOP (that is, on the lean side of peak EGT) at 70 or 75% of power, but only 25 LOP at 55%. This was interesting to learn, though the actual impact of the information on fuel consumption is probably very slight. Braly also alluded to the well-known general principle that best efficiency is achieved at the lowest rpm and highest manifold pressure consistent with engine limitations; but the applicability of that rule is influenced by the propeller, which may become less efficient, not more, at a given true airspeed, as rpm drops. The loss of prop efficiency with diminishing rpm is very gradual, however, and so it may not really be a significant factor at all.

Unfortunately, the more optimistic view of the efficiency of the propeller, while in no way affecting the performance of the airplane, has obliged me to revise my estimate of its CDo from 0.0214 to 0.0222. How humiliating!

[March 11, 2008]

I finished riveting the flap synchronizer frames today -- my rivet gun couldn't manage the 3/16-inch AD rivets, but my 12-ton hydraulic press upset them nicely -- and was able to mock the thing up to better visualize the plumbing. It looks kind of cool, if you don't realize how stupid it is.

[March 9, 2008]

Although I can't operate my flaps yet, I can analyze them with CFD. Here are a couple of images of streamlines that I found very interesting. The first view, from above, shows the large amount of spanwise flow associated with the deflected flap, and particularly the vorticity generated at the flap root. The second view -- same streamlines -- is just to clarify the relationships in the first. Streamline colors correspond to pressure, and therefore inversely to velocity, with the red end of the spectrum being low pressure/high velocity, green neutral, and blue high pressure/low velocity. The green color of the model is arbitrary.

[March 7, 2008]

In the last three days I've flown twice to Mojave to look in on Ray Henning and his T-18, and once to Apple Valley to touch bases with John Roncz. Roncz had unexpectedly gone to Tehachapi, so I missed him, but the air was very smooth and so I was able to perform the test of cooling drag described on February 16. At 8,500 feet and my customary cruising fuel flow of 8 gph, which is about 55% power, opening the cowl flaps seemed to reduce indicated airspeed from 139 knots to 137. The two-knot difference corresponds to 0.1 sq. ft. of equivalent flat plate area, or about 5% of the total parasite drag.

I chased the T-18 for a while yesterday while Mike Melvill and Ray flew in the T-18. It climbs very well -- 1,500 fpm up to 8,000 feet at Mojave (field elevation 2,538) -- and the airspeed indicator matched mine, which is accurate, perfectly. Ray had earlier mentioned a high cruise of 168 mph indicated at 10,000 feet, which works out to over 200 mph. And he has not yet put the wheel pants on. He has the odd-looking Thorp pants, which cover only the inner half of the wheel; the stock joke about them is that they only slow the airplane down a little. Here's how it looked through my optically imperfect rear window; the dry lake is on Edwards AFB, and the snow-covered peak is 10,000-foot Mt. Baldy in the San Gabriels:

I'm getting close to assembling the flap synchronizer frames. They involve a great many parts that took forever to fit and drill, but I hope to rivet them Monday if I manage to alodine them over the weekend.

[February 24, 2008]

While I grimly revisit the Gestalt of metal airplane construction by drilling holes in what will be the frame supporting the flap synchronizer, others are more interestingly occupied. Last Tuesday Ray Henning trailered his blinding T-18 to Mojave, where Mike Melvill, never one to waste any time, helped put it together and then took it out for a test. The wind was gusting to 29 knots by the time he was on the runway, and besides the tailwheel steering was unacceptably sensitive, so he confined himself to a short lift-off. Yesterday, after replacing the tailwheel springs, Mike made a flight that was cut short after 15 minutes by the non-operation of the alternator and consequent loss of radio communication. Apart from the electrical problem, everything was good, including -- always importantly -- the stall.

I feel a bit envious, like someone who has college-age kids and whose friend has a new baby. Ray, I suspect, must be greatly relieved and impatient to fly the plane himself. He will have to be careful to avoid any heading that places the sun in a position in which it reflects into the cockpit from a wing. The joke going around Mojave is that the airplane took four years to build and 12 to polish.

[February 16, 2008]

Back home, and flew for a little while. I was looking for smooth air in which to perform a simple test. I was curious whether opening and closing the cowl flaps affects overall drag enough to have a noticeable effect on speed. I've never detected any, but I thought that perhaps a more sensitive test than indicated airspeed would be vertical speed. If I trimmed for level flight with the cowl flaps closed and then opened them, the plane would begin to descend if the drag increased. After repeating this test a few times, I ought to begin to get a consistent impression. Unfortunately, today was not the day. It was bumpy at all altitudes.

Costa Rica hands with birdwatching proclivities will marvel to learn that I took this picture within 12 hours of arriving in the country:

[February 6, 2008]

I'm going to Costa Rica fora weeka. M2 is staying here. No exciting updates til I return.

[January 29, 2008]

During a break in the rain late last week I flew seven touch-and-gos. I've never flown touch-and-gos in Melmoth 2 before, and they turned out to be instructive. I realized that because I usually approach the airport on a long straight-in from the northwest, I had grown accustomed to flying the VASI glide path from a couple of miles out. That was a mistake; it's way too shallow for my airplane or, I suspect, any light airplane. Besides, Whiteman has a telephone pole sticking up right at the end of runway 12, and even though I probably clear it by 30 feet I always feel as though it's about to gouge a hole in the underside of my wing. If you're on the VASI glideslope and miss the pole by a good margin, you have to drop down rapidly to land on the numbers and make the midfield turnoff -- which I seldom managed to do. Flying a series of circuits I realized that a steeper approach felt more comfortable, made for a more natural flare, and allowed me to touch down on the numbers.

For about a week I've been working up the courage to ask one of the local shops if I could use their shear and brake to make the channel elements for the flap synchronizer. A lot of shops, and individuals, don't like to let visitors use their equipment. Today I finally got up the courage to ask. I hadn't even finished the sentence when the mechanic said, "Sure, come on over, they're right there." I had all the parts made inside of an hour.

[January 22, 2008]

Today I found, in a nondescript metal building on San Fernando Road, just east of the old home of Industrial Metal Supply (where, between 1968 and 1973, I bought most of the metal for Melmoth 1), a sheet of .050 2024-T3, which I need for the synchronizer frame. It's become quite difficult to find aircraft alloys in small quanities -- "remnants", as they're called. Industrial, in a new and grander location a mile away, now carries only 6061-T6 and 5052. 5052 is too weak and soft to be of much use, but 6061-T6 is suitable for some applications and is weldable, unlike the stronger aircraft alloys 2024 and 7075. Burbank Metal Supply resembles the old Industrial in miniature, with stacks of miscellaneous materials, aluminum and stainless steel, some pristine, some scuffed and scratched, leaning against walls and stacked in racks. Irv Kaye, who walks very fast and has a somewhat scholarly air, was friendly and helpful, digging through piles of sheet until he found the one, two by three feet, that I needed. It cost $25 -- about eight times what it would have cost when I was building the first Melmoth.

Now I must find someone equally cooperative who will let me use a shear and brake to cut and bend the parts.

I should explain again what this synchronizer does. The flaps are hydraulically operated and are tapered, so the outboard actuators travel a shorter distance than the inboard ones. The job of the synchronizer is to apportion the flow of hydraulic fluid to the actuating cylinders in such a way as to keep the tips and roots in the proper relation to one another and to make sure the flaps move simultaneously. The four cylinders in the synchronizer do this by moving different amounts, kept in step with one another by the single bellcrank to which they are all attached.

Burt Rutan has repeatedly said that I don't need flaps -- his Catbird, an airplane similar to mine, doesn't have them -- and it's true that I have been flying for five years now without them and without missing them. But when I said a few days ago that this was a case of art for art's sake, I could have been speaking of any number of aspects of my airplane that are not really necessary -- or for that matter of the airplane itself.

[January 17, 2008]

Having assembled the cylinders and begun to mock up the flap synchronizer on a piece of tooling plate, I am beginning to feel that this is a case of art for art's sake, unjustifiable by any rational calculus balancing effort and reward. To say nothing of weight. But now that I am this far down the road, I may as well continue.

[January 5, 2008]

Yesterday I spent a couple of hours machining a few final pieces for the flap synchronizing system. One of the things I did was take a little material off each of four end caps for the cylinders. These are 3 inches in diameter, and I took away material to a depth of .140 in. over a width of about .6 in. It disappeared into a mess of chips and didn't look like much, but if you calculate the volume removed it turns out to be about a quarter-pound of aluminum. I guess that was worth 20 minutes. As someone in rehab from Christmas, I can testify that machining is faster than dieting. So those parts are at last done, and this afternoon I degreased, acid-etched, and alodined them in the kitchen sink.

[January 1, 2008]

Well, that's over.

Yesterday was the first time in a week that I've gotten out to the airport and either flown or worked on the plane. I did a little of each.

Nobody has ever asked what the Latin quotations on the home page and on the "Cooling" essay mean. But I'll explain anyway. The one on the home page, "album mutor in alitem..." is from an ode of Horace (Quintus Horatius Flaccus, 65 BC - 8 BC), in which he somewhat grotesquely imagines himself transformed by the fame of his poems into a far-flying bird; literally, it means "I am miraculously changed into a white bird, and light feathers sprout from my fingers and shoulders..." It gets weirder when his legs develop crusty chicken skin; but enough. On the "Cooling" page, the phrase is from the Transformations (usually called "Metamorphoses") of Ovid (Publius Ovidius Naso, 45 BC - 17 AD, a sexy old goat). Telling of the schemes of Dedalus for escaping from imprisonment on Crete, he wrote that the mythical tinkerer "sent out his mind into unknown arts," namely, flight -- sort of like me fumbling around with engine cooling, an art not called "baffling" for nothing.

It never ceases to amaze me that these 2,000-year-old texts come down to us intact.

[December 20, 2007]

Having leaned toward using composites for the supporting framework for the flap master cylinders, I leaned back toward aluminum after reflecting about just how, in detail, I would achieve the desired bearing strength at the cylinder pivots and compressive strength between them. It seemed as though it would be a comparatively complicated layup (two of them, in fact, since the apparatus is sandwiched between two frames, mirror images of one another), with very little weight saving, if any, over an aluminum trusswork of simple bent-up channels riveted to corner gussets of 1/8-inch plate. The corner gussets will be the bearers for the cylinder pivots and the central bellcrank (the "starwheel") to which they are all connected.

It was not until this afternoon, actually, that I ran through all the numbers to ascertain exactly what the stresses are. I am apparently of the "Build first, analyze later" school of design, like the people who did that bridge in Minneapolis. Actually, there were no surprises, since I had a good approximate idea of the forces involved just from mental calculations which I perform, in a fanciful effort to stave off Alzheimers, while falling asleep at night. The main piece of enlightenment that came out of today's more formal calculation was that it is not necessary to regulate the hydraulic pressure in the master cylinders to a lower level than that in the bleeder cylinder; all can run at 500 psi without inflicting excessive loads on the structure. I still need to machine five clevis fittings to join the the hydraulic cylinders to the starwheel, and then I believe it'll be O-ring and hydraulic fluid time.

My hangar neighbor Ray Henning, who has finally finished his T-18 (I think it's been about 30 years in the making), gave me some nylon tubing which will be an excellent, and economical, alternative to the many Aeroquip hoses I had stupidly intended to use.

It will be truly disheartening if this elaborate apparatus does not work as planned.

[December 9, 2007]

Yesterday Captain Tom Huff, the CO of the Naval Test Pilot School at Patuxent River, Maryland, stopped by on his way to the Air Force Test Pilot School graduation at Edwards, and we flew to Camarillo for lunch. I had him fly the plane on the way there, hoping for his assessment of it. Of course if he had thought it stank he probably would have been too polite to say so, but I got the impression that he liked it pretty well. For me, it was a pleasure to watch a skillful and precise professional pilot -- Huff is an F-18 guy, mainly, but he also flies a 210 -- fly my plane, after watching myself fly it for so long. I imagine that playwrights and composers seeing their work performed get a similar pleasure; another person brings something fresh to your perception of the familiar thing. Huff made a nice landing at Camarillo, and I made a rotten one at Whiteman, just to round out the experience.

I've been working steadily on the flap retraction system; the main thing that remains to be made, apart from the center tracks, is the frame that holds the four synchronising cylinders in the proper relation to one another. Originally I was planning to make it of .080 aluminum plate, but at some point it dawned on me that the loads between mounting pivots of the cylinders and that of the starwheel that keeps them in step with one another are compressive, and therefore need something with better column properties than thin plate to keep them in place. I kicked around various options and am currently planning on composite; it seems like the least expensive option, and the simplest to tool.

[November 28, 2007]

On September 17 I wrote about removing the fuel filter and finding in it a great deal of debris consisting, mostly, of bits of carbon fiber and light-colored grit that I think must be epoxy particles released by sanding. I discovered today, to my very great surprise, that by simply holding my Canon PowerShot A80 against the eyepiece of my microscope I can take a pretty good photomicrograph. Here are three shots, the first of the (almost) clean side of the filter, the second of the dirty side, and the third of some of the powder that I scraped off the filter surface. The carbon fragments are on average a couple of thousandths of an inch long.

[November 13, 2007]

I flew up to Paso Robles again, this time to talk with a machinist, Richard Galli, who is creating 10 reproduction LeRhone rotaries for Javier Arango. Everything on these engines is machined from huge hunks of solid steel billet -- no castings -- and Galli seems to me a genius with a mill and a lathe. I have no idea how he manages to make some of these parts -- which were originally made, however, in 1915, with machines much inferior to his but, he says, with no less precision in the final results.

The flights up and back -- about an hour each way -- were very smooth, with visibility unlimited and cloudless skies and an OAT of 9 degrees C at 12,000 feet. The autopilot and GPS tracker are working again; now I need to learn the millions of features of my old but highly serviceable Lowrance. So far, like, I suspect, many pilots, I have pretty much confined myself to the "GOTO" command. The other day I could have used the "runway extension" feature, which draws a line several miles out from the runway centerline. It was so murky in Los Angeles that I couldn't see Whiteman's VASI lights until I was inside two miles.

The plane seems to me to have slowed down a bit; I need to put it up on jacks and see whether the landing gear doors have gone out of adjustment. Then again, maybe the overall coating of dust and ash is disturbing the laminar flow.

[November 6, 2007]

I changed my oil today. It took three hours. Every time I do it I promise myself that I will come up with some kind of quick-drain to replace the stock drain plug; but I never get around to it. The problem is that there is very little room between the drain plug and the nose strut in its extended, and even less in its retracted, position. Getting at the plug to remove it is difficult, and made more so by the fact that the engine and the oil are hot. There are various kinds of quick-drains on the market, but even the "low profile" one in the Spruce catalog looks to me as if it takes up too much space. I need a drain that protrudes no more than 1/4 inch below the boss on the sump. I have an idea of how to make one, but as the misery of the oil change recedes in memory I will probably lose the impulse to do it, just as I have on every previous occasion.

[October 31, 2007]

Just got back from almost three weeks on the east coast, where, among more ordinary activities, I logged .7 in a Black Hawk at Pax River. Having been relieved of most of its military equipment, it climbed 3,000 fpm straight up.

By the way, the Peter Garrison who flew a Seneca into a building in Vancouver on October 19 was not I. I am not sure which of us was the real Peter Garrison, but in any case I am now the remaining Peter Garrison.

[October 5, 2007]

On Tuesday Russ Hardwick and I flew up to Paso Robles for lunch at Michael's, an airport restaurant of the better sort or, better, a restaurant of the better sort that happens to be located at an airport. We parked in front of the restaurant, alongside a handsome Lancair 360. After lunch we got into a conversation with the owner of the Lancair, who had bought it from someone who had had it built by a professional builder. "There are the people who like to build," the pilot declared, "and then there are the people who like to fly." Obviously, he preferred to fly and assumed that I preferred to build.

On the return, while descending into Whiteman, I throttled the engine back to idle and compared rates of descent with fine and coarse pitch. (The subject was on my mind because I had written in a couple of recent Aftermath columns that glide can be extended by putting the prop in coarse pitch.) Fine pitch, which causes the engine to turn at higher rpm and therefore absorbs more energy, yielded 1,200 fpm, against 1,000 fpm for coarse pitch. Now I am curious to know the zero-thrust sink rate; theoretically, it should be around 750 fpm under the same conditions. This figure, which emerges from my computer simulation, implies that the engine is absorbing about 15 horsepower when the propeller is in coarse pitch. I have a 1972 Lycoming report, Peformance Characteristics of the Continental IO-360-D Model Engine, which includes a plot of friction horsepower against rpm; it shows a nearly straight-line variation between 12 hp at 2,000 rpm and 28 hp at 2,800 rpm. (A close fit, if anyone cares, is 5.16x^2 - 4.27x.) I'm not sure whether this includes pumping losses, which could be at least partly eliminated on the test stand by plugging up the intakes and exhausts. I'm also not sure whether it's better to have the throttle open or closed in a power-off glide, or whether it even makes an appreciable difference. A vacuum cleaner runs faster with its intake plugged, but it's not a positive-displacement pump and so the analogy may not be a useful one.

To measure zero-thrust sink rates, I would have to put a microswitch on the engine block behind the propeller flange and detect the point at which the crankshaft, which has measurable end play, shifts from thrust to drag. Knowing the zero-thrust sink rate is one way to measure drag; the rate of sink represents the release of potential energy at a known rate, and can be translated into horsepower at least as reliably as fuel flow can.

Speaking of sink, I tried a lean climb on the trip to Paso. Rather than climb at 1,000 fpm at 28/2500 and 12 gph with a rich mixture, I set up 27/2400 and 8.4 gph at about 50 deg. F lean of peak, which gave 500 fpm. I later ran the math and found that the lean climb saves 0.2 gallons or, at current prices, about 90 cents; on the other hand, it takes about three minutes longer to cover the first 40 miles of the trip. Is my time worth 30 cents a minute? Depends whom you ask.

On Wednesday and Friday I worked at Homer Knapp's machine shop -- he is a motorcycle machinist and pilot whom I first met in the early 1970s in John Thorp's circle -- on the flap synchronization cylinders. They are now honed and the barrels and caps are threaded. There is still some machine work to do on the caps, but the honing and threading operations have loomed before me for years now and I'm glad to have them finally taken care of. Homer did the first three barrels and had me do the fourth, which I only slightly messed up. I did the inside threads on all four caps without ruining any of them -- a minor miracle.

On Thursday I bit the bullet and took my autopilot over to Mid-Continent Instrument at Van Nuys airport for repair; I also removed my quaint eight-day wind-up clock, which would run for barely eight minutes on a full winding. I thought it needed cleaning, and took it to the local watch repair place in Echo Park only to learn that the elderly horlogier had "passed." For the past two days, however, the clock has been ticking away merrily on my drafting table, evidently more at home there than in the airplane. Perhaps, like many people, it prefers lying on its back.

I got a message this afternoon that the autopilot is fixed and the bill is $185. Not bad for an airplane part. I can amortize it with 200 lean climbs.

[September 20, 2007]

I flew around for half an hour just to remind myself of where the buttons and knobs were. I was somewhere north of the San Fernando Valley, climbing through 6,000, scanning the sky like mad because this is the area through which flights inbound to Van Nuys and Burbank pass, when I briefly looked at the instruments and then looked out again to see a King Air passing in front of me a few hundred feet away. It was incredible that I could have failed to notice it moments earlier, since I was being quite conscientious about looking for traffic. It's difficult, after an experience like this, to have a lot of faith in "see and avoid." It also makes it seem particularly strange that Cessna's new light sport airplane, the 162, which is featured on the cover of Flying this month in a picture so murky that the airplane can barely be distinguished from the background, is a perfect clone of the 150, an airplane so notoriously difficult to see out of that its mere existence demonstrated the value of pure chance in avoiding midair collisions. Evidently the designers at Cessna, who should know, feel that visibility plays a relatively minor role in air safety.

[September 18, 2007]

I found the filter element at Kal Nelson's, or rather at K&P International, which has replaced Nelson's, the disappearance of latter enterprise being, as an employee of the new one said to me with a mysterious smirk, "a long story." After installing the new filter element, I cut the old one apart. It consists of 27 square inches of resin-coated paper. Under the microscope it is revealed to be a dense tangle of glossy orange fibers whose diameters are on the order of a few ten-thousandths of an inch. I found that the dirty side was loaded with a lot of debris but far from clogged. None of the long glass or carbon fibers had found their way to the clean side, but a few particles of amorphous whitish stuff resembling salt had, together with some very small fragments of carbon. Some of these, however, may have been transferred to the clean side by my less than professional handling of the sample. The filter seems on the whole to have been very effective. Possibly, however, it would be a hazard in freezing conditions if there were any water in the fuel. If the filter, which has no bypass, managed to become clogged with frost, it could shut down the engine. It would perhaps have been better to put it in the engine compartment, where it could have been kept warmer and would, besides, have been easier to get at.

The pictures below show the compartment that is below the pilot's thighs. The airbrake has been propped open to allow access to the compartment. The black object with the groove down the middle that runs across the top of both picures is the main spar. The filter housing is the bright aluminum thing on the left. Immediately to its right is the fuel shutoff, whose handle is on the other side of the bulkhead; to the right of that is the gascolator -- a genuine antique. Then comes a shaft that is part of the backup manual gear-lowering mechanism, and then, vanishing from the edge of the picture, is the electric boost pump. The next picture takes up where the first leaves off, with the electric boost pump (the red and maroon thing with the yellow label on the bottom); the two aluminum valves are fuel tank selectors, one controlling feed and the other return. They may be operated manually or electrically; the motor is the tan cylinder above the valves. The two springs are return springs for the airbrake, which is the black surface at the bottom of the picture; the cylinder that operates the airbrake is just above the springs. The back end of the hydraulic pump is at the extreme right.

There are some photographs of the other end of this action-packed compartment at January 31, 2007.

[September 17, 2007]

I have been making the fairings for the middle flap tracks at a relaxed pace, one a day. Today, having finished the fourth of six pieces, I thought I would go flying, but then decided first to drain the sumps and gascolator and check the fuel filter. The fuel tank sump drains disgorged, as usual, a few largeish grains of this or that -- you can never tell what the stuff is -- and no water whatever. They have never shown any water, although the tanks are never close to full; I suppose this is my reward for living in a dry climate. Often one or the other of them begins a slow drip after being drained, and it becomes a big production to get rid of whatever bit of smut is sticking to the tiny O-ring. This time that didn't happen, and I proceeded to the gascolator, which is located above the airbrake in the wing centersection. It always drains very slowly, yielding a deep blue liquid -- the dye in the avgas seems to collect here -- and a small amount of finely divided black grit that almost looks like some sort of melanoprotozoa when random turbulence -- or Brownian motion -- stirs it up. The gascolator, too, was kind enough to re-seal without starting to drip.

I then opened up the fuel filter, which, just between us, I have not looked into since 2002. The filter uses a pleated paper element, and there was quite a lot of scum in it; in fact, when I had mined most of the stuff out of the pleats it amounted to perhaps half a cubic centimeter of what appeared, once dry, to be a fine gray powder. Under a microscope, however, it revealed its true identity: a pick-up-sticks-like maze of black and transparent shafts of graphite and glass, mixed with clumps of shapeless light-tan debris which I take to be epoxy dust. Using as a gauge one of Nancy's hairs, which, by the way, was astonishingly clean and regular in shape, resembling an acrylic extrusion, and which I mic'd at .0017 inch, I estimate that the fibers are about two or three ten-thousandths of an inch in diameter. Most are three or four thousandths long, but a few are as long as .010 inch. I'm awfully glad I put in the filter; most airplanes don't have extremely fine fuel filters like this, but the debris the filter caught could have caused no end of trouble in the injectors.

I imagine that the filter element must be pretty well riddled with this gunk, and that I need to replace it rather than attempt to clean it. (It is customary, in any case, to replace paper filters and not to re-use them.) The element is a Purolator part, AN6237-1. I thought I had a couple of spares, but I could not locate them in the hangar. (Actually, it would have been miraculous if I had.) The local parts shop, Vista, didn't have one, but said they could get one by tomorrow. I decided instead to try my luck at Norton Sales, which has incredible amounts of incredible stuff, but, incredibly, didn't have this. I then thought I might find it online; all of the places offering it for sale, however, are electronics parts suppliers, so I'm afraid that if I order one I'll end up with a capacitor or something instead. Nothing at Aircraft Spruce. I'll try Luky's tomorrow -- the somewhat diminished avatar of the once magnificent Joe Factor Sales -- and then Kal Nelson; if those fail I'll be back at Vista, where I hope it doesn't turn out that they can't get them after all.

[September 8, 2007]

I revisited the stress analysis of my flaps more than three years ago (see March 11, 2004), and found that the loads that I assumed when I built them in the first place, some time well back in the twentieth century (why didn't I make my programs print the date on everything?), coincided closely with the new calculations -- showing, for one thing, that the old methods worked as well as the new ones, at least for this sort of rough analysis. But I have no records of what calculations I used to size the attachment points for the middle flap track. There are receptacles in the rear spar for four 1/4-inch bolts, two top and two bottom. The bolts are certainly adequate; but what provisions I made in the surrounding structure to spread the tensile and compressive loads, equal to the weight of a small car, into the skins and ribs, I don't know. I must have assumed, since I was completely absorbed in the design at the time, that I would never forget its details. Now, 15 years later, I have. I have lots of photographs of the wings under construction, but none of them shows how the lower attachment, the one in tension and the more critical of the two, connects to the ribs and skin, or what local reinforcements I may have added to the sandwich core, or whether I locally doubled or tripled the skins (as I should have). There are a few shots of the upper attachment, and I assume the lower ones were similar. In any case, they no longer seem to me adequate. This is a critical area, because a failure here would threaten the integrity of the aileron pushrods, and so I am having to redesign the attachments from scratch, more or less as though the original hard points did not exist. This should never have been necessary; one should document everything, either with drawings or photographs, no matter how unforgettable it seems.

My ancillary interest in Latin has drifted away from Vergil and, because my daughter will be reading Ulysses later this year and I am revisiting it after an absence of 45 years, alit upon a bit of ecclesiastical hocus-pocus to be intoned over the dying: liliata rutilantium te confessorum turma circumdet. This seems to me to mean "May a lily-bearing throng of blushing spirit-guides surround you." Perhaps some pilot-priest, if such there be, could set me straight about these inexplicably rosy-cheeked confessors. It is interesting to note, by the way, that the wish that follows this one is "iubilantium te virginum chorus excipiat" which means "May a chorus of rejoicing virgins receive you." Evidently, Muslims are not the only ones who expect to be greeted by virgins at the pearly gates. Seriously, however, it's quite obvious that the virgins here are symbols of angelic purity, and we may as well assume that their Islamic counterparts are as well, and not the frolicking lapdancers that many people seem to suppose.

[September 6, 2007]

Through good luck, it turns out that the fairings for the outboard flap tracks (see October 26 or December 4, 2006) will also work for the middle ones, and so I can re-use the original molds. This is the opposite of what usually happens, which is that I plan a part to serve several purposes and then find that it really won't serve any. Each fairing consists of three parts. It always feels as if it should be possible to make several at once, but today I managed just one. No hurry.

I have been thinking a lot lately about how to translate the famous line of Vergil, sunt lacrimae rerum et mentem mortalia tangunt. Taken in isolation it seems very beautiful and poignant and has a Japanese pity-of-things flavor, hardly the sort of thing you expect from pius Aeneas. In context I think the effect is much more mudane. But this matter is probably more suitable for some other website.

[August 29, 2007]

On the 22nd I had lunch with Mike and Sally Melvill at Mojave. In an effort to prevent the inside of the cockpit reaching the boiling point of plastic while the airplane was parked -- 20-knot winds made it impossible simply to leave the windows open -- I spread a white sheet over the seats and most of the floor. This seemed to help, although the Safe Flight angle of attack meter was still frozen when I took off -- heat has that effect on it -- and didn't begin indicating until ten minutes into the flight. It seems as though the cover ought to be on the outside, although it is awfully inconvenient to have to stretch a big canopy cover over the airplane in a stiff wind. I wonder how I dealt with this problem in the first Melmoth; I don't remember it being a big concern, other than the one time I burned my hands on the seatbelt buckle after parking in 114-degree temperatures at Palm Springs.

In the week since then I have not flown; I have been making a few final additions to the left flap, and next week will do the same to the right.

[August 16, 2007]

On the 14th I flew up to Oakland for lunch and returned in the afternoon. Southbound a little north of Gorman I had to get an IFR clearance to penetrate the smoke from a fire -- it is called the Zaca fire, I have since learned -- that I had somehow remained unaware of until that day, but that has been burning for a month in the mountains north of Santa Barbara and has consumed 84,000 acres. Just before I entered the opaque smoke, there was an extraordinary view to the west of a wedge of turquoise sky between layers of russet; unfortunately, I didn't have a camera with me to capture it.

During the flight I observed the continuous slight -- two or three amp -- charging of the battery that I have come to recognize as the sign of low battery water; I checked it yesterday and it was indeed low. This unexpected charging was a great and seemingly alarming puzzle a couple of years ago; now it's just a piece of routine service.

My progressive shaping of the seat back cushion is paying off; it seemed quite comfortable (but the flight, admittedly, was short -- less than two hours). Now I feel as if the seat bottom needs a deeper hollow for the buttocks, which will result in more thigh support. I'm taking off just a little at a time; I don't want to go too far.

[August 14, 2007]

Yesterday I had an opportunity to re-weigh the airplane. It has gained 180 pounds since its first flight, lord knows where, and now weighs about 1,575 empty. I have to say "about" because there was around 53 gallons of fuel aboard, and I have to say "around." The empty CG has also moved aft by more than an inch. The news from scales is seldom good. I was trying to comfort myself when I happened upon the specifications of a Cozy Mk IV, which supposedly weighs 1,000 pounds empty and cruises at 220 mph on a 180 hp Lycoming. That made me feel even worse.

[July 24, 2007]

While preflighting the plane on Friday I noticed what appeared to be a nut lying in one of the small drain holes that are supposed to let rainwater out of the cowling. Opening the side of the cowl, I discovered that the object was actually the head of a bolt. The nut was lying nearby. They had previously secured the turbocharger to a brace that is intended to keep it from vibrating fore and aft. I had just read a few days earlier that one should not use self-locking nuts in the engine compartment, and this seemed to bear out that rule. I replaced the bolt, whose threads were peened flat, with a new one of the drilled variety, and I replaced the self-locking nut with a castle nut and cotter pin.

I learned yesterday that Hans Georg Schmid had died in the crash of the Express 2000 in which he had intended to make two circumnavigations of the globe via meridians. He had just taken off from the airport at Basel, Switzerland, bound for Oshkosh, a 5,000-mile nonstop -- he loved long flights, and had circumnavigated the Earth before in a VariEze (or Long-EZ, I'm not sure which) -- when he either encountered downdrafts or could not develop full power, and struck the roof of a building a couple of miles from the runway.

I felt some connection to this project because my friend Hans Kandlbauer had been its chief engineer and aerodynamicist; I had also helped design the tip tanks. Although the airplane was very fully equipped (glass cockpit, etc) and loaded with 450 gallons of fuel, it had a 315-hp Lycoming and should have had a pretty reasonable rate of climb. For reasons that are not yet clear, Schmid, a retired Swiss Air Lines pilot with 16,000 hours, had elected to take off southward, with a light wind behind him and rising terrain and buildings ahead, whereas if he had taken off northward he would have been flying over flat and unpopulated terrain. The airplane was relatively unproven; it had just emerged from its 25-hour initial flight restriction, and this was, I believe, the first time it had flown with a full fuel load. Below, the airplane on its first flight, June 13, and Hans Georg in the shop in December, 2005.

[July 12, 2007]

It is often the case that, once the answer to a question is known, one is tempted to see whether one could have arrived at it analytically.

Theory of Wing Sections (p. 195) gives a CL increment of 0.6 for a 20-degree-deflected plain flap. Assuming that because of the dropoff in the spanwise lift distribution near the tip the effective CL is only a third of the theoretical value, that gives 0.2 * 1.2 * 205 * .87 * q for the maximum rolling moment, where 0.2 is the CL increment, 1.2 is the area of the flapped portion of the tip, 205 is the distance in inches from the centroid of lift of the tip to the CG, .87 is the cosine of the dihedral angle, and q is the dynamic pressure, which is roughly 16 lb/sq ft at 70 kias (rotation speed) and 64 lb/sq ft at 140 kias (typical cruising speed). The rolling moments from a fully-deflected trimmer run roughly from 700 lb-in at the lower speed to 2700 lb-in at the higher.

The next question is: How do those values compare in magnitude with possible fuel imbalances? Using Loftsman's tank analyzing routine, I obtained the weights and spanwise centroids of fuel loads from empty to full and made the following graph, which shows the incremental effect of each unbalanced gallon of fuel:

Each wing can hold about 70 gallons of fuel. As fuel is added the CG of the fuel moves outward, and the space occupied by added fuel moves outward as well. Consequently, the moment contributed by each additional gallon increases much more rapidly when the tanks are nearly full. At cruising speed and full tanks, the trimmer can neutralize an imbalance of 2700/1200 or around 2.3 gallons; with a more typical fuel load of 40 gallons, however, the figure is nearly 7 gallons.

Analysis by Cmarc, using the inviscid option (which is somewhat unconservative, that is, optimistic) and fully-deflected ailerons, gives a rolling moment at 70 kias (close to the flaps-up stalling speed) of about 45,000 lb-in -- obviously sufficient to counteract any probable fuel imbalance. But it is also obvious that the effect of the roll trimmer is very small compared with that of the ailerons, and that an aileron trim tab would have been a more powerful roll trimming device. Duh.

[July 11, 2007]

I finally test flew the roll trim flap. The good news is that there is no noticeable adverse yaw or side force from full deflection; the bad news is that there is not much rolling moment either. At approach speed you can barely tell whether the flap is deflected or not. At 140 kias the effect is much more marked, but by the time you've reached altitude and accelerated to cruising speed the fuel imbalance that the trim is supposed to compensate for will probably have burned off anyway.

The flap travel is about +-20 degrees. I was interested to see that with the flap going downward, separation occurs at or slightly before half travel. The rolling moment continues to increase, but probably at a lower rate that it would if the flow remained attached. The hinge is in the upper surface; the lower surface has a well-faired radius at the joint, and it is possible that the flow over it remains attached up to a larger deflection; but I can't see that side from the cockpit.

It remains only to paint the flap and forget about it.

[June 29, 2007]

A correspondent (Frank Shoemaker) inquired about the kind of analysis needed for a modification like the addition of the trim flap. Another (Paul Lipps) wrote to point out that a spring trim on the stick works just as well, and is simpler than an electrically operated flap. I concede Lipps' point without debate.

How much analysis I would do would depend on the type of movable surface I was adding. In this case, it is a trailing-edge flap attached to a MAC servo. The servo is a linear jackscrew, and so the flap is locked in position at all times and is not susceptible to flutter. (Even if it came loose from the servo, I think that it is too small and light, and the wing is too massive and stiff, for mutual excitation to occur. That is just an intuitive judgment, however. The flap might buzz, or even tear itself off the wing.)

As far as stress analysis is concerned, I never did any stress analysis of the upturned tips in the first place. I considered it self-evident, based on experience with foam-cored structures, that they would be strong enough. They have a spanwise ply of unidirectional carbon in both upper and lower surfaces as well as the two-ply 45-degree glass torsion box. I also figured that even if one failed it would not be a safety of flight issue. After building them I tried to bend one and found it to be sufficiently stiff that in my opinion air loads would not break it at up to 200 knots (Vne).

One can, however, do a back-of-an-envelope stress analysis. Dynamic pressure at 200 knots is 132 lb/sq ft. CFD analysis of the spanwise lift distribution suggests that the tips achieve only about 60% of the CLmax of the wing at their root (BL 200), tapering to zero at the tip. With the trim flap set 20 degrees down I would very conservatively assume an average CL of 1.0 for the tip, which has an area of 1.6 sq. ft. Because the tip tapers from a root chord of 21 inches to a tip chord of only six, I would put the spanwise centroid of pressure 5 inches from the inboard end of the tip. This works out to a compressive load in the skin at the root of 1.6 * 132 * 5 / 3 (3 is the section depth in inches), or around 330 pounds. This root moment can be simulated with a 20-pound force applied (by hand) to the tip of the structure. Of course the moment curve is different; a concentrated load at the tip puts an unrealistically large bending moment at mid-span. But in any case this is a limit-load test, not ultimate.

The flap itself, which is piano-hinged along its entire leading edge, undergoes only torsional loads, for which it is manifestly adequate. I added a strong rib to the inboard end, with a nutplate where the actuator attachment goes, and bagged a two-ply layup over it to ensure shear continuity between the end rib and the skin. There is no rib at the outboard end.

In the process of adding the trim mechanism, I hollowed out some of the foam core at the root of the left tip; also, making the trailing edge into a movable flap interrupted the torque box. To remedy these defects, I closed out the cove, added a glass shear web where the foam now ends, closed the nose of the flap, and placed a four-ply reinforcement in the unsupported portion of the upper skin, which, as a thin curved compression member, is the most critical element in bending. The reinforcement also serves as an anchoring surface for the servo motor. Most of these modifications are in the aft portion of the tip, however, whereas the principal load is carried by the fore portion, which remained unchanged.

When putting a flap on a swept panel, you always have to choose between aligning the end gaps with the airstream and making them more or less normal to the trailing edge. The latter option avoids interferences, but I find it aesthetically unacceptable, and so I opted for the former, with the result that the end gaps have to be larger than I would like.

[June 24, 2007]

Having hacked up the left winglet in pursuit of the nonexistent pitot leak, I decided that I may as well put in the roll trimmer. This involved cutting up the winglet even more, but by now I was hardened to it. I have a little trim motor that I bought in 1987, and have been storing since then in a cool dry place, for this very purpose. The trimming surface is a flap on the winglet. Because the winglet has a 30-degree dihedral angle, the trim surface will actually produce some lateral force that will have to be neutralized by the rudder. Probably it will be too small to notice, and in any case the point of the trimmer is just to reduce the stick force due to a temporary fuel imbalance at the beginning of a flight. Imbalances occur mainly when the plane has been parked for a long time on a slanted surface, or one main gear strut is less fully inflated than the other. It's just been a minor and occasional annoyance up to now, but I can imagine that with more fuel that I usually take on, and the center of gravity of the fuel consequently farther outboard, it could be quite a nuisance. On the other hand, when I get around to moving the aileron hinges aft in order to provide more aerodynamic balance and reduce their hinge moments, an asymmetrical fuel load may not be such a problem.

[June 14, 2007]

I finally got the pitot-static sign-off today. Adjusting the transponder was not excessively expensive. The funny thing was that when we repeated the pitot test the pressure still bled down. Then it finally occurred to me to ask the technician to remove his test attachment from my pitot tube and put his thumb over the end of it and repeat the test. It still bled down. So the leak was in their equipment, not in my system.

[June 12, 2007]

Wrong. That was not the leak. Today, at first, I concluded that the leak must be in the pitot head itself. I extracted it from the wing with some difficulty and submerged it in water while pressurizing it with my dental gadget. A stream of bubbles rose from what turned out to be a drain hole that was clogged with something or other. I cleared the hole, and then when I covered it the pitot head held pressure. But it now seems as if the whole system is holding pressure, so something I did at some point in the last two days, I don't know what, must have sealed the mysterious tiny leak, wherever it was.

The radio shop, of course, has not yet even looked at my transponder.

[June 11, 2007]

It was surprisingly difficult to locate the leak. I tried pressurizing the system and painting all the joints with soapy water, to no avail. I broke the plumbing down into segments and tested them one by one, using a dental syringe (quite a handy thing, actually; you're supposed to squirt between your teeth with it, I suppose, but it just happens to generate 200 knots in the ASI when fully compressed) and an inches-of-water gauge that I had forgotten I had, but found in a cabinet while looking for a second ASI. I sawed out a chunk of the trailing edge of the left tip and dug out the blue foam stuffing to uncover the short length of vinyl hose that runs from the pitot tube to the 3/16-inch aluminum tube that connects the wingtip to the instrument panel. I finally concluded that the slow leak was where the vinyl tube slipped over the copper tube sticking out of the pitot, which is the standard heated type. I hope I'm right; if it's not there, I have no idea where else it could be.

[June 10, 2007]

I took the plane to the local radio shop for the biennial pitot/static certification, which is required even for VFR flying here because Whiteman is within 30 nm of LAX. The first problem that arose was a leak -- slow, but not slow enough -- in the pitot plumbing; the second was that the transponder's pulse timing had drifted off and was outside the tolerances for the test (the end result being that it transmitted inaccurate altitudes, even though the encoder was generating accurate ones). The radio guy who I hope will be able to fix the transponder was away for the week, and so we borrowed an AT50A from another airplane and completed the altimeter and encoder checks, which were fine. I'll find out Tuesday about the transponder -- I have a bad feeling the guy is going to say, "Can't fix it, you'll have to buy a new one, but here, we have a great deal for you." Meanwhile, I've been trying to track down the pitot leak. I have a feeling that it's where the tip extensions attach to the wing, which is bad, because I was uncharacteristically reckless there and made no provision for getting access to the pitot tube. Now I'm going to have to cut some holes in the tip to get at the thing, but I guess I can view this as a divine nudge toward installing roll trim, which an airplane with full-span fuel tanks needs.

[June 3, 2007]

I made round trips to Mendocino and to Paso Robles in the past week. Nancy was with me on the Mendocino trip, and she didn't find her seat, which used to be the pilot's seat, overly comfortable. I didn't love the new pilot's seat either. I decided that one problem was that the seat back was not sufficiently concave (about an axis parallel to my backbone), and so support was mainly being provided to the center of my back. I ground some more concavity into the seat back after that trip. It felt better on the hangar floor, but on the next trip, an hour-long flight to PRB, I felt that my back was getting sore again. By this time I was starting to wonder whether the whole business was not just my imagination, but I tried putting a lumbar support, which I unzipped from a little seat-cushion-plus-lumbar thingum that I had from Oregon Aero, behind me. That immediately felt a great deal better, and seemed pretty comfortable for the return trip -- or at least it allowed me to feel that the locus of dissatisfaction was now the seat bottom rather than the back.

I used to get a sore back (and shoulders) playing the piano. I wonder whether it's really that certain activities, among them flying and piano playing (for me, at least, and possibly for those who heard me play), produce muscle tension that is absent when, say, I am sitting in a movie theater or in an easy chair reading a book. Or, more likely, I am simply getting older, and more prone to aches and pains. I don't remember the seat being a major source of concern when Nancy and I flew for 15 hours from Alaska to Japan in 1976; and Melmoth 1's seats were much cruder than Melmoth 2's.

The trip to PRB was for Chuck Wentworth's annual barbecue at Antique Aero. A whole slew of interesting airplanes showed up, including, among the military types, a Zero, a couple of P-40s, a Sea Fury, and the expected herd of Mustangs. Most of these were extremely spiffily painted and polished, but the one I liked best looked somewhat war-weary, its aluminum dull and its paint chipped. It looked like the real thing.

[May 23, 2007]

Russ Hardwick and I flew to Page, AZ on the 21st to visit a couple of slot canyons. I had been working for the past week on the duct that leads air from the flush scoop on the right hand side to the controllable ventilator (from an '89 Camry) for the back seats. The duct is a fairly elaborate thing with a diffuser about a foot and a half long (a diffuser is a gradually expanding duct, intended to reduce the velocity of air flowing through it without allowing the flow to separate from the tunnel walls). At the end of the diffuser is a flow reverser that turns the air about 150 degrees and feeds it into the ventilator, which faces forward because the seats face aft. The reverser even has a turning vane in it; it's all very fancy.

When Russ and I left for Page, I hadn't yet tested the ventilator in flight and I didn't know how much air would come out of it. I did know that there was no way for people in the front seats to adjust the ventilator, but I figured that it was a warm day in LA and it was warm in Page, and so it wouldn't be a problem if it were open.

It was already apparent when we were taxiing that the ventilator was doing a pretty good job. It really went to town after we took off, discharging torrents of air into the cabin. This was not too objectionable at first, but then we climbed higher and higher to stay above the inversion and the turbulence, and the outside air got colder and colder. The ventilator happened to be aimed right between the two front seats. My right shoulder and Russ's left froze until we let down at Page. It's remarkable that a NACA scoop more than ten feet back from the nose of the airplane, where the boundary layer must be pretty thick, and behind the point of maximum fuselage width, can still pull in so much air.

[May 9, 2007]

I flew to Santa Ynez for lunch. The air was extremely calm -- groundspeed exactly matched true airspeed -- and I got a good speed point. Speed takes a very long time to settle down -- several minutes. As I have often mentioned before, I determine drag area (or drag coefficient -- they amount to the same thing) by comparing observed performance with computed performance, using the performance prediction routine in my lofting program, Loftsman. The computer output is one or two decimal points more precise than in-flight observation; for example, when my fuel flow indicator flickers back and forth between 6.9 and 7.0, I call it 6.95, but it could be any number within two or three hundredths of that. Airspeed can be measured within maybe half a knot, assuming zero calibration error. Here is the Loftsman output for a weight of 1,900 pounds, a density altitude of 10,400 feet, and a power setting of 26 in Hg and 2,000 rpm. The collective EGT was about 60 degrees lean of peak. Indicated airspeed was 133 knots.

The items, from left to right, are true and indicated airspeed in knots, drag in pounds, thrust horsepower required (a function of speed and drag), estimated propeller efficiency (based on a highly generalized curve), brake horsepower required (which is thrust horsepower required divided by propeller efficiency), percent of rated power, ratio of parasite to induced drag, engine specific fuel consumption (again based on a generalized curve), fuel flow in gallons per hour, specific range (that is, nautical miles per gallon), and, finally, the "CAFE" product of true airspeed and miles per gallon. The highlighted line corresponds to yesterday's measurement.

The last item, which I call the CAFE product because it was the crux of the scoring formula for the old CAFE efficiency races, is related to the "Carson speed", the speed at which you get the "best" combination of speed and efficiency (as distinct from the L/D or best range speed, at which you get the best efficiency, regardless of speed). The best speed to fly, on this basis, would have been closer to 140 kias.

Cylinder head temperatures, with the cowl flaps closed, were:

1. 175 C.
2. 170
3. 170
4. 170
5. 150
6. 180

On the return trip I used a slightly higher power setting (26.7/2,200, fuel flow 7.8 gph) and saw a somewhat different temperature distribution:

1. 185
2. 160
3. 180
4. 175
5. 150
6. 190

So the general pattern is: #1 and #6 are warmest, #5 (not #2, as I always thought) is coolest, and the others are somewhere in between. The previously observed coolestness of #2 correlated well with its being the first cylinder to reach peak EGT; it was therefore running leaner, and hence cooler, than the others. The present observation does not correlate with anything in particular, but suggests that the earlier pattern was just a coincidence. At this point the cooling is sufficiently well-behaved that I think I will just stop paying attention to it.

[May 8, 2007]

I realized yesterday that for years I have been referring to the left front cylinder as #5. It is #6. I went back and corrected the error all through this narrative (I hope).

What else have I been doing wrong for years?

Cylinders on my engine are numbered from back to front, with odd numbers on the right because the cylinders are staggered with the right side farther aft. (Multiple engines, on the other hand, when they are on the wings, are numbered from left to right, like freeway lanes.) My engine's oil cooler is mounted on the crankcase directly behind the #2 (left rear) cylinder.

The reason the lack of finning on the exhaust port surface is not a problem with downdraft cooling, I think, is that air emerges from the baffle passages at high velocity, and so heated air is continually scavenged from the unfinned surface. When the flow is going in the other direction, however, air converges into the baffle passages from a wide range of angles, and does not pick up a lot of speed until it enters the baffles. The revised baffle provides a converging channel over the exhaust port, and also adds baffling that wraps around the undersides of the cylinder, increasing the velocity of airflow there.

[May 5, 2007]

Success again. I redid the baffles on the right rear cylinder (which modification took three days rather than the expected one) and pulled its temps down by 50 degrees F or so as well.

Yesterday was a peculiar-looking day, with a shelf of dense clouds over the San Fernando Valley but lots of clear areas to the west. I started a 1,000-fpm climb westward once I was out from under Burbank's Class C. The CHTs were running around 150 C with the cowl flaps fully open. I closed down the aft vents to half an inch or so and went up to 10,500 feet without the hottest cylinders getting above 200 C. The target (ie factory recommended) temperature is 370 F or about 185-190 C. Continuing westward, I set up 27/2300, or around 55% (8.2 gph). With the cowl flaps closed as far as they would go (1/4-inch gap at the aft ends) the temps settled at around 150-175 C. (Different cylinders are still at different temperatures.) The oil temperature is still a rather high 97 C.

Incidentally, the reason I keep bouncing back and forth between Celsius and Fahrenheit is that my CHT gauge is calibrated in Celsius, while Continental's documentation is in Fahrenheit.

The #2 cylinder, the one next to the oil cooler, is still the coldest, and #1 and #6 are still the hottest, , but the disparities are much reduced. I guess that further tinkering with the baffling could bring the CHTs still closer to one another, but I'm not sure it would matter.

After pointing westward for a while I checked the GPS groundspeed and found that I was doing 90 knots. So I turned around, and then I was doing 220. Too bad I wasn't going to Arizona.

[April 27, 2007]

Success. The revised baffling on left front cylinder brought the temperature down by about 50 deg. F; it is now in line, +-20 degrees, with all the other cylinders save one, the right rear, to which I should be able to apply the same treatment next week. The problem with the cylinder is that it has no finning to speak of in the vicinity of the exhaust port:

My baffles previously ended even with the centerline of the cylinder; the trouble with that arrangement, as I now see it, was that it did not provde enough air velocity, and therefore heat transport, on the lower half of the cylinder. I modified the baffles by extending them down around the bottom of the barrel and the inboard part of the head, and providing a barrier about 3/4 of an inch away from the finless portion of the casting around the exhaust port. The revised baffle looks like this:

The way in which the baffle, which is lying down on my junkheap of a work table with its lower edge to the right, matches the cylinder should be fairly clear. I'm sure that still more improvement is possible -- the barrier near the exhaust port is pretty crude -- but this went a long way. Here's the way it looks installed:

[April 24, 2007]

It finally occurred to me -- showing that if I think about something long enough, even the most obvious fact about it will eventually become apparent -- that what my two hottest cylinders, the left front and right rear, have in common with one another is that their exhaust ports are not next to another cylinder. The suggestion is that whatever flow guidance is provided by a neighboring cylinder for cooling air passing by the exposed side of the port, which has practically no finning, is not being provided by my baffles. This clue at least gives me something to work with.

I should have the flap actuator plumbing finished by the end of this week and be able to resume working on the synchronising cylinders. It's increasingly clear that I won't have the flaps working by Oshkosh -- my somewhat arbitrary target -- unless some phase of the project proves less, rather than more, time-consuming than expected. That would be unprecedented, however. Well, maybe they'll be working -- but only on the ground.

[April 17, 2007]

The NACA scoop for back seat ventilation works nicely. I tufted the inside of the fuselage behind it, and the tufts were straight and steady in flight, indicating a strong flow with little turbulence. What I want to do now is diffuse it over a distance of about two feet and turn it around 180 degrees toward the back seats (which face aft). I sat in the new pilot's seat for this flight; it's not right yet. More foam grinding ahead. Cruised around for half an hour making squiggles on the GPS map. 137 kias at 7,500 ft DA, 7.6 gph -- a bit below par. It's interesting to note that opening the cowl flaps about 1/2 inch pulls CHTs down by 40 deg F, but does not have a measurable effect on speed. Tomorrow I think I'll wash the plane -- it's embarrassingly dusty -- and then get back to the flap hydraulics.

[April 13, 2007]

Two weeks later and I'm still installing hydraulic lines. It's weirdly time-consuming, to say nothing of expensive (AN and Aeroquip fittings are not being given away these days, unfortunately), but I'm getting there. I took a short detour this past week to cut a Concorde-shaped hole in the right side of the fuselage for an air vent for the back seats. I haven't flown yet to see whether any air actually comes in through it. It's one of those flush NASA affairs, and it's hard to understand how it can work very well once the boundary layer has grown to a depth that's comparable to that of the inlet channel. I'll test it on Monday.

I've also been grinding away at the foam on the pilot's seat and then sitting on it for a minute or two to see how it feels. It's hard to judge; even park benches feel comfortable at first.

[March 31, 2007]

Something about me seems to be extremely irritating to upholsterers. On Friday I was shown the door by the second one. I was not heartbroken; he seemed to me to be even less conscientious and competent than the first, who was no great shakes. But at least I ended up with a bunch of foam, glued rather haphazardly to the seat frame, at no charge. It's just as well that he decided to kick me out before he covered the seats, because the way he had shaped the foam was not very comfortable anyway. I'm going to try my hand at it, imitating the seats in my Geo Prism, which seem fairly comfortable.

In the meanwhile I've been adding the plumbing to deliver hydraulic fluid to the outboard flap actuators, and thinking a lot about an alternative cooling air intake configuration that might make it easier to equalize temperature among the cylinders. Just thinking; there are plenty of other things to work on first. But it's something to do while going to sleep.

Here's the environment of the outboard actuator:

The flap has been lowered to reveal the cove just inboard of the aileron; the latter can be seen, deflected upward, in the lower right corner. The diagonal pushrod is the aileron actuator, supported, in the upper left corner, by one of several idlers. An inspection plate has been removed, revealing the outboard fuel quantity sender (partially in shadow) and an aluminum block (bottom center) with blue fittings protruding from its top and bottom. The purpose of the block is to provide an anchor for the ends of flexible hoses going to the actuator, which will be installed just outboard of the aluminum flap track, between it and the fuel quantity transmitter. The paired lines, which run about ten feet inboard to the fuselage, are what I've been installing; they are 3/16 inch in diameter, and are secured to the upper surface of the cover at 15-inch intervals by tiny phenolic pillow-blocks.

[March 14, 2007]

I flew for half an hour to test the effect of the exhaust pipe insulation on the temperature of the left front (#6) cylinder head. It went up. This was not entirely unexpected; the exhaust pipe is in intimate contact with the cylinder head, and if stays hotter because of the insulation, some of that heat would migrate into the head. It was a question of whether the benefit of not preheating the air approaching the cylinder baffles would outweigh the ill effect of keeping the pipe hotter. It didn't.

A speed point -- density altitude 10,000 ft., weight 1950 lbs, fuel flow 7.5 gph, IAS 138.5 kts -- confirms once again the value of 2.25 sq. ft. for F.

I took my pilot's seat to the tapiceria -- upholstery shop -- across the street from Whiteman for an estimate. The amiable and copiously tatooed owner said it would be around $200 to do the second one -- $150 labor and $45 for the foam. I already have the covering material from my unhappy episode with the uphostery guy on the airport, who wanted half again as much money for the same job and then did it badly.

[March 12, 2007]

It was 90 degrees today, but there was a good breeze at the airport and for some reason the metal hangar does not become unbearable on hot days. Neddy, my large, long-haired and black dog, seemed pretty comfortable sprawled on the asphalt. I did some laminating in the back of the plane and noticed that for the first time this year I had to take care not to drip sweat on the epoxy-soaked glass cloth. The anchorages for the inboard flap actuators are now in place, and I have nearly finished making the hard points that will be secured near the outboard ends of the flaps to anchor the flexible hoses going to the actuators. Once those are in place, I will be able to plumb the hydraulic lines from the fuselage to the outboard actuators, and then get on with the synchronizer. On Friday, tired of fiddling with the flaps, I wrapped the exhaust pipe below the left front cylinder with insulating stuff, but I have not yet flown the plane to determine whether the proximity of the pipe is actually the reason for that cylinder running hotter than its neighbors.

[February 28, 2007]

I spent a jolly hour or two on my knees in the back of the plane, sanding out clearance for the flap actuator, which passes though a couple of bulkheads in a very confined space. At first I tried to do it with files, rasps and sandpaper, and I reminded myself of those patient prisoners who break out by filing their way though steel bars with dental floss dipped in floor dust. I then had the inspiration to saw a slot in a piece of 3/8" aluminum rod and slip the end of a 20-year-old, and hence tightly curled-up, piece of 40-grip Norton abrasive cloth in it. This, chucked in an electric drill, cut through fiberglass and plywood beautifully. At the end of an unusually long afternoon I had the left actuator working without interference though its entire travel. The right one will be easier because now I know what needs to be done, but harder because I'm right handed, and it's on the wrong side for holding a drill motor while hunched up on my knees.

[February 27, 2007]

I went to get some O-rings at A.C. DePuydt, Inc. I love that place. It's located in an LA suburb with the arresting name of Commerce. You go to the Will Call counter with your tiny order for a dozen rings. They always have what you want, even weird sizes without AN or MIL numbers, and after they're pulled it from inventory they send you around to the cashier, who is always charming, and in no time the invoice has been typed up and you're out the door with a little brown paper bag in your hand. This time the bill was $5.14. I think they have a $5 minimum; they give you extra O-rings to fill in the gap. I took them to the hangar, where a bunch of hydraulic cylinder parts that I'd made over the past couple of weeks were waiting for them.

I started to assemble the four hydraulic cylinders that will operate the flaps. I found that the silver-soldered joints between the shafts and the pistons for the outboard cylinders were leaky -- I submerged them in water and applied compressed air to the hollow shafts -- and I'll need to put some epoxy inside. On the inboard cylinders I had threaded the shafts and the pistons and used penetrating threadlocker, on the advice of my machinist friend Homer Knapp. They came out without any leaks. I then tried to assemble the cylinders and found that on one of them the hole in the end plug through which the shaft emerges was too small for the shaft. The shaft, which is a piece of surplus stainless tubing that I picked up at Industrial Metal Supply, mics at .378, and I've been reaming the bores with a .377 reamer. To enlarge the reamer I used another Homer trick, namely sliding a hard steel edge along the front of the flutes, which I suppose must raise a tiny burr. After I had done this several times the shaft finally passed and I was able to assemble the cylinders, one of which see below. The overall length of the cylinder in its retracted position is 20 inches. The next step is to fit them to the airplane, which I will do tomorrow -- or at least start doing tomorrow.

[February 21, 2007]

Machining, machining. The four actuating cylinders for the flaps are almost ready, and the synchronizing cylinders are about halfway there.

In the meantime, about three weeks ago I had delivered the structure for the fourth seat -- which was to be the pilot's seat -- to the upholstery shop on the airport. I took the guy the first seat he had done for me last fall and asked him to duplicate it, except that I wanted the seat cushion to be about an inch thicker and that there be more of a lumbar support at the bottom of the seat back. Several weeks passed, and then he presented me with a seat which was indeed one inch thicker, but only right under the buttocks, so that sitting on it was something like sitting on a watermelon: no thigh support, no lateral support. The lumbar bulge seemed to extend the whole height of the seat back, which was now flat rather than slightly concave as it should be. After one flight to see what it felt like, I took it back to him and pointed out that the first seat he had made was comfortable and well-formed -- so he obviously knew how to make a seat, which is, after all, what he does for a living -- but the new one wasn't. First he explained to me that this was my fault, because I hadn't had him make both seats at once -- although if I had, I would then have had two seats that were too low and lacked lumbar support, rather than just one. After some more discussion, he said, "All right, come back in an hour." I couldn't do that, but I came back the next day only to find that his knickers had evidently gotten into such a knot that he had stripped all the upholstery and padding from the seat frame, and refused to have anything more to do with it.

Well, I never liked the guy much anyway.

[February 10, 2007]

I spent the past week machining parts for hydraulic cylinders, averaging one mistake per three parts, and planning just how this flap system is going to fit in the airplane, how many of which kind of AN fittings it will require, and how the hydraulic connections will be bled. In Melmoth 1, which used two hydraulic flap actuators, one driven by the exhaust of the other, I used a kind of settling tower, consisting of a cylindrical fuel filter bereft of its innards and mounted upside-down, to capture air in the line connecting the two cylinders. I replenished the hydraulic fluid in the trap at fairly regular intervals, but never did know where all the air was coming from. The system for Melmoth 2 would require four such traps, one for each of the lines connecting the master cylinders to the flap actuators. I'll see how it works without them before installing them; the system, without air traps, works beautifully in my imagination.

Early in the week I also overhauled the left main gear strut for the second time. I had done so a few months ago, but it soon resumed leaking hydraulic fluid like mad. It turned out to have a rolled O-ring, due, I think, to an area of corrosion on the bottom of the groove which must have developed during the struts' many years of idleness. I bought the two Cherokee gear struts (whose outer shape was heavily modified for this airplane, but their inner workings are untouched) quite early in the project, back in the early 1980s, and they proceeded to sit around, along with the engine, for twenty years. I was able to clean up the rough area with fine sandpaper and the tip of my pinkie, but until I've made a few landings I won't be sure it's really fixed. The left strut also leaked air for the first year or so after the airplane flew, and then finally sealed itself up; that leak was up top -- as a general principle, air leaks out the top, fluid out the bottom -- and I have no idea what made it go away, other than the mysterious force that seals some leaks over time while it makes others worse. The right main, on the other hand, has been perfect, requiring neither fluid nor air in more than four years of operation.

[January 31, 2007]

The age of miracles is not over. I managed to connect the hydraulic flap control valve to the plumbing leading aft without taking the whole plane apart. I had to grind a 9/16" crow's-foot wrench down to a wisp, but it worked. One of the lines I installed was a remnant from Melmoth 1; I like incorporating little bits and pieces of the old plane in this one.

The two pictures below show the plumbing that is now complete. The upper one is particularly confusing. It is taken from beneath the airplane with the airbrake open and the cover that usually separates this area from the cockpit removed. The top of the picture is forward; the blue corrugated surface in the background is the hangar ceiling.

There are three physically identical valves in the picture (how many monkeys are hiding in the forest?). The one in the center, which controls the landing gears, is closest to the camera and looks larger than the others, but it is the same size and shape as the one in the upper left hand corner (airbrake) and the one at top center in the background (flap). My great accomplishment of the past two days has been to install the two vertical lines that run from the flap valve down to fittings below the main spar, which is the black object running across the bottom of the picture. For scale, the lines are 1/4-inch. Anyone who has done mechanical work will wince at the thought of tightening the nuts on the flap valve.

The valves are operated by cables running through Teflon-lined bicycle-brake-cable