Swing-Wing Falco
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Swing-Wing Falco |
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by Jonas Dovydenas This article appeared in the September 1993 Falco Builders Letter. The weather was so bad this past winter, I rarely flew the Falco. The one time I went out in January, I had to taxi between fifteen-foot-high piles of airport snow to get to a heavily sanded, icy runway. Before the winter was over, we were to get 130 inches of snowfall. The problem became what to do with myself and the Falco. One day, I came across a promotional package from the Cirrus people and was tempted to begin building again, but a simple calculation showed that the time required to complete would use up 39.5% of my remaining lifespan, assuming I lived that long. So, instead, I chased the racoons out of my attic, repainted the hangar floor for the third time, and put a couple more stick-on bullet holes on the Falco. This got me through a week of February. Then my friend Gandanauskas called from Kalushubov, in the Trans-Caucasus, to tell me his whole department was out of work. The Computing & Research section where Gando worked was downsizing because of the demise of communism. "It's all Reagan's fault," he said. "We were in the middle of some interesting work with plasma flow in an environment of a hundred million degrees and ten million bars pressure when the Party went belly up, just like that. Now I can't even pretend to work for my pretend pay. Can you get me a green card?" I told him green cards take forever to get, but an idea occured to me. Back when I first told him I was thinking of building a Falco, his only words were "I know all about your project. Do it, you won't be sorry." A year later I ran into him in Moscow and asked him during a walk. "So explain how you knew about the Falco." "Well, aerodynamics is a hobby of mine. I helped a glider shop with some airfoil designs. I never told you before, but once, in a vault in Cheliyabinsk I came across a set of Falco plans and a technical analysis. Don't ask how we got them, we had everything. There was a stack of books in the same vault all written by this guy Bingelis. Sounds vaguely Lithuanian. Do you know him? Anyway, every time someone would send one of these books, the KGB would steal from the post office and lock it up. But getting back to my story, I read all the reports on all the homebuilts, and the Falco is in a class by itself." All I could say was, "That's what I'm hearing from everybody I talk to." That was six years ago, now I was asking him, "Could the Falco be improved?" There was a long pause on the line. "Ah, that's a really interesting questions. I can look into it. Give me a week." As it happened, he called back in three days. This is how the swing-wing Falco modification was born. "Look," he said, "my friends and I ran the numbers in our heads over four bottles of Polish vodka. Just for fun, we started with the SGDE [single governing differential equation]. I remembered the main design points and dimensions, and each of us made three or four totally wild, even improbable assumptions for modification. Then all of us ran through three or four iterations. That alone took care of two bottles. We couldn't believe it. That Frati's some genius. Just under his design lurks a real monster. We looked at more than ten parameters, but in the end all we did was change four coefficients, normalized the Pandtl equation for non-elliptical distribution, threw out some third derivatives and made sure the resulting solutions weren't somehow squirrelly. To our surprise, most of the problem factors and numerical clutter dropped out, and 20.6 degrees of wing angle popped out." "Oh, that's good," I said. "If you want to go all the way, swing the wings and swap your prop set-up for an 800-lb-thrust APO unit. You will go supersonic without even feeling anything in the stick, that's how well designed the Falco is. Of course, you'd have to re-balance the control surfaces, beef up the flap actuator brackets and a few other things, but those are just shop problems. If you keep the prop, you will see a 65% increase in speed in cruise." Good ol' Gando, I'm thinking, he's still drunk. "Look, it boils down to this: I need 565,000 rubles so I can pay off the machine shop guys. The only way the numbers work is if the hardware is made out of titanium. Anything else adds too much weight." I asked him how much that was in dollars. "Uh, let me think, that's about $127." I told him the high cost was not going to deter me from going ahead. "Okay, give me a couple of days." I waited two days to call Gando. "It was a piece of cake!" he said (actually in Lithuanian he said a "slurp of sour cream" but the idea's the same). "I told the guys in the machine shop I'd give them two extra bottles and a smoked ham from my parents's farm. They did it overnight! I'm giving the package to a driver today. We're sending er, ah, some interesting metals to North Korea by boat from Klaipeda. The driver's my buddy, he'll give it to UPS, two-day air delivery, COD, okay? By the way, send me some BIC throwaway razors. I can get 5000 rubles apiece for them here, and you know, there's still no toilet paper here, so I'm losing a lot of blood shaving with our so-called safety razors." The package came, and I have to tell you, it was impressive. A set of five virgin mylars, and copies on good paper. A hundred some pages of instructions and data, albeit in Lithuanian. Every part vacuum-packed, dated and bagged in heavy Russian plastic, with little bags of desiccant. Builder's heaven. I will give you a full report of the shop work in a separate article, if you think anyone's interested. But it was a snap, really. Gando had figured 46 hours. I did it in 152. Not bad, huh? The hardest part was putting the Sawzall to the spar, but there was a jig included in the kit. Gando knew my hands would be shaking. After cutting the wing and replacing the existing gearbox with Gando's titanium box and wing-pin, I was ready for flight tests. I wanted to use Al Aitken again, but he was on a trip for the airlines, and I couldn't wait. In wings-forward mode, the roll response is spectacular, even a little touchy. After a standard climb-out to 7,000 feet, I leveled out at 100 knots and pulled up the wing-pin lever. This engaged gears and activated a microswitch. Slowly backing off the throttle, I saw the airspeed go up as the wings went back. When the gears clunked into automatic lock, I was 8 knots shy of Vne with 19 inches of manifold pressure and 2300 rpm. Gando's numbers were very close. I said to myself, that's good enough for me. Fuel burn was 8.1 gallons. Roll response was spectacular, even a little touchy. There seemed to be a good deal of noise in the cockpit from the high speed. Otherwise it was the same familiar Falco. I was elated but needed to change my shirt and other clothing. Turning back to the airport, the swing-wing Falco just would not slow down to pattern speed. Keeping my eyes on the CHT numbers, I made three turns around Pittsfield to enter the pattern. Cycling the gearbox in the wing-pin mode got the wings straight again, re-cycling in the landing mode got the gear down. I was limp with the thrill of it as I drove home from the airport. If there's any interest out there for this modification, I'd like to hear about it. Gando's still out of work, and Polish vodka has not yet been replaced by a gold-backed ruble. And if any of you out there have a BIC distributorship, you're in luck-Gando's ready to deal. Jonas Dovydenas (shown here on the top of a loop at 15,000') lives in
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