Don't Need No Stinkin' Wings

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A few months ago, the talk of the internet was a YouTube video of a stunt plane that lost a wing in flight and nevertheless managed to land safely. Many people in many countries sent me this video; the subject lines of the first few e-mails, which came from pilots, tended to marvel at the display of coolness and flying skill. The next wave, which came from nonpilot friends, displayed a more robust skepticism: Is this really possible?

My own first reaction on seeing the video was that it was a fake, not only because I strongly doubted that the maneuver was even possible, but also because of internal evidence. The wing broke at the wrong time, during a low-G maneuver. The exclamations of onlookers, heard in the background, don't have quite the tone of fascinated dismay that the spectacle of the imminent death of a human being usually evokes. The airplane lands right in front of the camera -- already a suspicious detail, since unexpected and freakish occurrences seldom allow for ideal camera placement -- and the dynamics of its landing are unrealistic. The airplane seems to have almost no momentum, but just bounces sharply once and stops. It just looks like a model, the way ships being tossed by storms at sea in old movies look like toy ships.

The tape was evidently a composite of footage of a real airplane and footage of a radio-controlled model rigged to jettison a wing. The more I viewed it, pausing here and there, the more discrepancies became visible. The shapes of the two airplanes were not quite the same; in particular, the nose of the real airplane was longer than that of the model -- a detail that is, in a way, related to the fundamental implausibility of the event. The stump of the missing wing, clearly visible during the landing sequence, does not look quite ragged enough to be the scene of an actual wing failure.

It struck me that this was an awful lot of trouble to go through to create a YouTube video -- the very quintessence of trivial ephemera. But after a few days debunking documents began to appear on the web, and it transpired -- I had not followed the links to the interview with the heroic pilot -- that the whole thing was a promotion for a German clothing brand. It was a form of "viral advertising" -- the ingenious stratagem of attaching a promotional message to something that then spreads through the internet, at no charge to the creator, under the power of its intrinsic interest or shock value.

(While we're on the subject of YouTube, if you want to see some neat tricks by a real live guy who really enjoys his flying, take a look at "Highland dead stick landing" and "STOL Highlander hilltop landing.")

Further rambling through the farrago of jewels and junk that is YouTube led me to a couple of videos -- search for "Bill Hempel" and "R J Gritter" -- that made it plain that landing after deliberately losing a wing is a fillip that has lately been added to the repertory of jaded RC pilots. The envelope of RC acrobatics is larger than that of piloted acrobatics, although piloted exhibition airplanes are capable of tricks that would not have been considered possible a few years ago. And not actually being inside an airplane whose wing had come off is a great aid to retaining one's presence of mind.

It's all a matter of power or, more precisely, power-to-weight ratio. (I should say thrust-to-weight ratio, but "power" is colloquial shorthand for the ability of engine-propeller combinations to generate thrust.) RC airplanes can have thrust significantly greater than their weight. Full-scale airplanes can too, but only when they're standing still. In airshows one sees airplanes hang from their props, like helicopters. It's surprising, but not that implausible: Static thrust in pounds is four or five times rated horsepower, and so may be equal to the weight of a small airplane with a powerful engine. Full-span ailerons, which extend into the propeller slipstream, can cancel the torque reaction, just as the tail rotor of a helicopter does.

When you're missing a wing, any lift from the remaining one produces an uncontrollable rolling moment. Any lift you're going to get has to come from the fuselage in knife-edge flight -- that is, lying on its side. You see the model airplane do this in the fake video; it's quite nose-high -- maybe 30 degrees, where the lifting component of the thrust would be half the total thrust -- and although a narrow, streamlined object like a fuselage lifts very inefficiently -- that is, it produces a lot of drag for its lift -- it does lift enough that, in concert with the vertical component of the thrust, it allows the airplane to maintain altitude or even climb.

The model's advantage over the full-scale airplane is its huge excess thrust. The model can not only hang from its prop; it can climb vertically from a standstill or recover from a steep descent using only rudder, fuselage lift and engine thrust. The piloted airplane can hang from its prop only after using wing lift to get into the vertical attitude, and can maintain altitude in knife-edge flight only at a narrow range of speeds. The engine of the model is more dominant: The airplane goes wherever it's pointed.

Putting all this together, and apart from the telltale visual discrepancies, it was evident from first principles that no full-scale airplane could do what the model did -- that is, recover into controlled flight from a spin after the loss of a wing, climb vertically, fly an approach from downwind in knife-edge, roll level just in time to touch down, and stop in a few feet. (A pilot, on the other hand, might possess the required sangfroid. The late British acrobatic pilot Neil Williams experienced a partial spar failure in a Zlin in 1970. One wing began to fail upward, and Williams rolled inverted, flew an approach and rolled out in the correct direction to avoid overloading the failing wing.) On the other hand, the fact that it can be done by a model shows that it could be done by a piloted airplane with a similar thrust-to-weight ratio, regardless of the differences due to scale effects. Now that the trick's potential for worldwide celebrity has been demonstrated, I'm sure that it will only be a matter of time until we see an airplane with a turbine or rotary engine lose a wing in an airshow and land safely. Heck -- why lose just one? Why not both?