Melmoth 2: A Personal Airplane

Blustery winds blew through Mojave for three days after the FAA signed off my certificate of airworthiness, but it was quiet on Halloween morning. I taxied out to Runway 30, where I had done many fast taxi runs before.

"Two Mike Uniform's ready. It'll just be a runway hop."

There are two schools of thought about runway hops. One holds that any unexpected flying quality, for instance a tendency to porpoise, is more safely dealt with away from the ground, and also that the first landing should be preceded by some approaches to stalls at altitude; therefore a first flight should be an up-and-away one. The other holds that it's better to fall four feet than 4,000. After mulling over these propositions for some time, I decided that I found the briefer one the more persuasive.

I made three short hops that day. I suppose I was airborne for about 10 or 15 seconds on each. Subjectively, it was impossible to tell. There were no surprises; except that I was moving a little faster, it was no different from flying a Cherokee. Still, there's a curious emotional transition as the wheels leave the ground on a first flight. I'm looking for the combination of speed and deck angle at which lift equals weight. Suddenly it's there, the texture of the runway surface under the wheels vanishes, the airplane gives a little sashay and then settles down perfectly steady and solid. Throttle back to hold altitude, and the crisis-which is entirely mental in any case-is past. I'm flying this airplane as if it were any other.

Later that day, I picked up my repairman's license at the local FAA office. "Now," the FAA guy said, "you can work on it." The point of his joke, of course, was that he knew I had been working on it for the past 21 years.

When I built the first Melmoth in 1968-1973, it was unusual in being larger and more complex than most other homebuilts. Jane's All the World's Aircraft generously called it a "lightplane research prototype." With its 210-hp Continental IO-360-A engine and constant-speed prop it was quite powerful for the time, and it had hydraulically retractable landing gear, double-slotted Fowler flaps, cockpit-adjustable aileron incidence and a cruising range of more than 3,000 miles. It had a 48-inch wide cabin and a windowed baggage area so large that a third passenger could ride in it. It eventually acquired IFR avionics, automatic fuel-tank cycling, airbrakes, an all-flying T-tail, an autopilot, a turbocharged engine (of slightly lower rated power), and a built-in oxygen system. It could cruise at 200 knots at 17,000 feet. This was at a time when the typical homebuilt was something more like a Wittman Tailwind, Midget Mustang or a sport biplane. Today many homebuilts far surpass it in performance, but I think that if it had not been demolished in a 1982 runway accident, the original Melmoth would still lead the pack in sheer gratuitous complexity.

In the late '70s, entranced by my friend Burt Rutan's seemingly effortless and rapid creation of novel prototypes, I yearned to build something with composites. I imagined it would be quicker and easier than the metal Melmoth had been. I toyed for a while with a push-pull canard twin I called Garuda. Rutan informed me that its high-wing-low-canard configuration was ill-advised-it puts the wing in the canard's wake at high angle of attack, risking a deep stall-and I eventually realized that I couldn't afford the purchase and upkeep of an additional engine anyway; so I set that design aside.

Then, with a baby in the offing, I decided to build a new, stretched fuselage for Melmoth so that the little tyke would have a nicer place to sit. At first I naturally thought of just adding a plug to the existing fuselage. That would have made a lot of sense, but it would have meant grounding the airplane for quite a while, and besides, I still wanted to try a composite project; and so in August, 1981, to show me how it's done, Rutan and Mike Melvill came down to my hangar and laid up the inner skins of the top and bottom shells of the aft end of a new fuselage.

Melmoth was wrecked about a year later. Accordingly, I designed a new wing and recontoured the bottom of the still-incomplete fuselage to accommodate it, sincerely believing that by working hard I could get the new airplane built in a year and a half. What an idiot! Ten years later I was still working in my home garage, which by this time had so much junk packed around the fuselage and wing centersection that I had to crawl on my hands and knees to get from one place to another. Progress had almost ceased. In 1992, I finally moved into a hangar. The vast space made a difference; suddenly reinvigorated, I moved ahead rapidly. Nevertheless, another 10 years passed before I finally flew the quick, easy-to-build, all-composite Melmoth 2-still not entirely finished.

I did try to think of a new name, but I couldn't come up with anything incomprehensible enough.

The required 25 hours of "Phase One" flight testing at Mojave were over just before Christmas, and I brought the airplane back to Whiteman Airport in Los Angeles. Almost half of the hours, and all of the really useful ones, had been flown by Mike Melvill. A professional test pilot, Melvill, who, unlike me, is not given to dithering and hesitation, did all the scary stuff: the first stalls (which turned out to be unremarkable, although without warning) and the flight envelope expansion to demonstrate freedom from flutter at high speed. He also spontaneously fixed things that broke, made improvements and provided hangarage, tools, help, advice and encouragement. I can't say enough about Mike, and so I won't try-but this world needs more people like him, and fewer of a lot of other sorts.

Once back at my hangar I woke up to the fact that, being within a 30-mile radius of a Class B airport, I couldn't continue to operate without first installing a transponder. There were many other things to do as well-minor repairs, and modifications of systems whose original design I'd thought better of-and Melmoth 2 ended up spending 10 weeks in the hangar before I got back to flying it.

One of the more time-consuming changes was to the landing gear retraction system. Recoiling from the snakes-nest of hydraulic piping under the seats of the first Melmoth, I had built this landing gear with all three struts mechanically connected and operated by a single hydraulic cylinder located six inches away from the hydraulic pump in the wing centersection. There are no up-locks; the retracting arms rotate to an overcenter position to hold the gears up. There are no sequencing valves; bellcranks and pushrods open and close the doors.

This arrangement works well in all respects but one: it has a poor mechanical advantage at the gear-down end of the cycle. This is not a problem for the mains, because they want to fall into place anyway. The nose strut, however, extends forward, against the wind. I knew well in advance that there would be a limit to the amount of aerodynamic resistance the system could overcome, but I satisfied myself, by calculation and by practical test (namely, placing a weighted cardboard box in front of the tire), that there was sufficient power to get the nosewheel down and locked.

As I described in February's Flying, the first time I retracted the gear in flight it would not lock back down. I tried again and again while Mike, flying chase in his Long-EZ, observed from below. After what seemed like an eternity of trying-it was probably less than five minutes-we hit upon the (in retrospect obvious) expedient of slowing to 80 knots and throttling back to idle, and the gear locked down.

Thereafter, this procedure became routine, but I never exactly enjoyed it. Once back at Whiteman, I installed both a gas spring and an additional hydraulic cylinder in the nosewheel well. The three struts are still mechanically linked to one another. I plumbed the new cylinder into the system by digging a trench in the foam-cored cabin floor and burying the lines in it-coincidentally at the same time as a new water main was being installed in a similar fashion under the street on which I live. The gear now operates normally, and even free-drops and locks at 100 kias, and the water pressure at home is better too.

Melmoth 2's many similarities to its precursor are partly due to their overlapping histories. But even if the second airplane hadn't begun life as a modification of the first, I would probably have designed it similarly. In most respects the first Melmoth had met my expectations, and there was little about it that I disliked. Besides, I don't have that much confidence in my abilities as a designer, and so I'm afraid to try anything too new.

The principal changes between Melmoths 1 and 2 are composite construction in place of aluminum; a tapered high-aspect-ratio (11.6) wing rather than a rectangular low-aspect-ratio (6) one; updraft cooling rather than downdraft; a fixed stabilizer rather than an all-flying stabilator; four seats rather than two; and a sidestick in place of a floor stick.

Less consequential changes include a belly- rather than wing-mounted speed brake, stouter main landing gear with 600 x 6 rather than 500 x 5 tires, and a single-slotted Fowler flap of larger area and smaller angular deflection (30 degrees versus 45) than the first airplane's double-slotted one.

Even though the differences between the two Melmoths are no more than evolutionary, Melmoth 2 is still a completely new design. The only components common to the two airplanes are the 200-hp turbocharged Continental TSIO-360-A engine, 76-inch Hartzell constant-speed propeller, hydraulic pump, instruments and avionics, and various bits of small hardware.

You would expect the new airplane, with half again the wingspan, to climb better, and it does; at 100 kias, with two people and 30 gallons of fuel aboard, it pegs the 2,000-fpm vertical speed indicator. It seems to be slightly faster than the first Melmoth in level flight, in spite of being larger; and I may still pick up one or two knots from nosewheel doors, flap track fairings, canopy seals and refinements to the engine cooling. My performance target was the same 200 knots or so at 17,000 feet, which means, most of the time, 175 ktas at 10,000, using around 10 gallons per hour. It does that now. It's less nimble than the first Melmoth, however, partly because the span is larger and the ailerons are relatively smaller, and partly because the stick forces in roll are higher than I would like.

Takeoff acceleration is very rapid. I rotate somewhere around 70-80 knots. Initial climb speed is around 100 knots, using 32 in. Hg and 2500 rpm. Approach speed is around 80-85 knots; I rely on a Safe Flight angle of attack indicator more than on the ASI to hold the approach attitude. The stall speed has not been measured since a properly calibrated static source was installed, but with the original static system it was 68 knots with power and 62 without.

People ask why I opted for the T-tail. The simplest answer, from among several equally plausible candidates, is that when I built the first Melmoth T-tails were in fashion and therefore, as fashionable things always do, they seemed a natural and superior choice. The sequence of events that led to Melmoth 1 having a T-tail was actually a bit more complicated than that-it started life with the stabilator on the fuselage-but once I had it I truly liked what it did for the airplane. In particular, it made for reliably smooth landings, which I attributed to the wing getting into ground effect before the stabilizer and producing a nice, effortless roundout. And so, if for no other reason than not to lose that quality, I stuck with the T-tail on the new design. It worked; Melmoth 2 lands in the same smooth and effortless way.

I abandoned the all-flying tail, however, for two reasons. First, I felt uneasy about the change in dynamic balance that occurred when ice collected on the leading edge. Second, I felt less confident about spreading its highly concentrated pivot loads into the composite structure than into the metal one.

I can't yet say whether all of the changes I made were for the better. The longer wing certainly was-but that's no surprise, since wingspan is almost always beneficial. The composite construction proved to be much more complicated and time-consuming than I anticipated. No doubt it's quicker for very simple airplanes and for prefabricated kits, but for a complex airplane like this one it's more difficult than metal. This airplane is, however, a little cleaner than the first, and it's likely that the credit belongs to the smooth, compound-curved surfaces and the lack of external antennas.

The fixed stabilizer seems fine; I won't know for certain until I've flown with a forward CG and full flaps. The sidestick, with its low mechanical advantage, is probably mainly to blame for the rather stiff-feeling ailerons. On the other hand, it leaves the floor completely clear, and with no console between the seats you can move your feet and legs about freely and stretch out on long flights. I expect that some day I might change the hinge points on the ailerons in order to provide them with some aerodynamic balance; but for the time being they're acceptable.

The updraft cooling is adequate, but it's not as good (at least not yet) as the downdraft was. I was surprised and disappointed that it wasn't immediately superior. I expected the placement of the cooling air exits near the front of the top cowl-a location that makes some people mistake them for inlets-to yield a powerful extraction effect, especially in climb. Maybe it does, but I still have work to do on the cooling; it's a complicated business.

The wing area, 106 square feet, which is the same as the old Melmoth's, is quite a bit less than the 170 or so typical of production four-seaters. John Roncz designed the low-drag laminar-flow airfoils, of which three are used, tapering from 18 percent thick at the root to 13 at the tip. They are similar to the ones on the Rutan Catbird, an airplane that mine in many ways resembles (by coincidence; neither of us was aware of the other's design). The tricky part of designing the airfoils was to avoid a premature tip stall on a strongly tapered wing with a very short tip chord (20 inches) and little twist or "washout." Roncz succeeded brilliantly; the stall begins at the root and progresses outward, as if the wing were rectangular.

The wing skins are principally of foam-cored sandwich, about three-tenths of an inch thick, with a load-bearing graphite inner skin and a just-along-for-the-ride outer skin of glass fiber. The spars are graphite. The entire wing, except for the flap cove and the extreme leading edge, is a fuel tank with a total capacity of 142 gallons. The outer panels bolt onto a central wing box that is integral with the cabin structure and protrudes two feet beyond the sides of the fuselage. The main landing gear is mounted in that box and the wheels retract under the seats-a feature that, combined with upright seating, obliges the cabin to be a couple of inches taller than it might otherwise be; but I could not get the 600 x 6 tires to disappear completely into the wing root.

I made the wing skins in four different female molds, and because of the lack of space in the garage I had to destroy each mold before making the next. Luckily, the parts fit together when I joined them. Other than the wings, cowling and canopy frames, however, I built the airframe without molds, by laying up glass- or graphite-epoxy over shaped plastic-foam cores. Two or three years into the project I discovered vacuum bagging-curing parts inside an evacuated plastic bag, so that excess epoxy is squeezed out by atmospheric pressure-and after that I vacuum bagged almost everything, whether it made sense to do so or not.

At Mojave, prior to first flight, the airplane weighed 1,397 pounds empty. By the time it's fully equipped, it will weigh about what the first Melmoth did-1,500 pounds. Proportionately, that's a reduction-remember, it's a bigger airplane, with heavier landing gear and canopy and a longer, more slender (and therefore theoretically heavier) wing. I hesitate to attribute the improvement to the composite structure-small composite airplanes usually turn out heavier, not lighter, than metal ones-but I don't know where else to put it.

People are often curious about the cost. I already had the engine, propeller, instruments and avionics from the previous Melmoth, and various friends were kind enough to donate materials, like graphite cloth, that would have been very expensive to buy. On average, I spent less than $1,000 a year on the project until it was close to flying and I started having to overhaul or repair long-stored items. I suppose I put about 500 hours a year of labor into it, some years more, some less.

It's still very much a work in progress, and will remain one for a couple of years to come. The flaps and speed brake, although built and installed, are not yet operable. The nosewheel doors are not installed, nor are the cowl flaps and wingtips. There are no nav lights or panel lights. Window seals, ventilation, heating, oxygen system, automatic fuel tank switching and intercom are among the functional amenities still missing.

As a project like this nears completion, the designer-builder finds less and less freedom of movement in it. A restless inner me, like some poor baffled mental patient who all day long repeats an abortive gesture, keeps wanting to return to the drafting table and the computer and to the thrilling, seductive first steps of design, when each line laid down is pregnant with new promise and beauty. But twice is enough; I don't think I'd better go around again.

Also read these related stories:

Melmoth Flies… Again!

Cleaning Up Melmoth

Five Years With Melmoth 2