Wright Brothers: Little Known Secrets to their Success
Not that they were strangers to stability. They did add a vertical stabilizer to their 1902 glider. A fixed surface, it provided the rectangular biplane with a preference - albeit a mild one - for flying forward rather than diagonally. It did little to counteract adverse yaw, however. The Wright brothers observed while gliding that when they warped their wings the airplane banked one way, but its "nose" — figuratively speaking, for it had none — swung the other. Wilbur had the insight that the additional lift of the upgoing wing entailed a resistance ("drift," he termed it). A good deal of sideslip was required to induce the short-coupled fin to do its job, however, and the brothers decided to connect the vertical rudder to the warping apparatus, thereby combating the adverse yaw from the moment it began. This arrangement was only partly successful; eventually they would disconnect the rudder from the warp on their later powered aircraft and allow the pilot to operate it as a third control.
The marked droop of the 1903 Flyer's wingtips is a puzzling feature, until you consider that they were in the habit of flying just a few feet above the ground.
Without the negative dihedral, a side-gust tended to lift the upwind wing, driving the other downward. They rigged "arch" into the wings of the Flyer to neutralize this effect. When they began to fly higher up and unintended ground contact was no longer a problem, however, negative dihedral ceased to serve any purpose and in fact made flying more difficult.
Bearing in mind that the natural stability of aircraft with aft-mounted stabilizing surfaces was weU known in 1900, one has to wonder why the Wright brothers chose a canard control surface instead. One had only to glance at a weathervane to suspect the canard of a natural tendency to swap ends. The only way to make it stable was to load it up by shifting the center of gravity forward. But the center of gravity of the Wright machine was quite far aft, perhaps because they found that by placing it there they could overcome the natural tendency of their cambered wings to pitch nose-down.
I've seen various explanations for the Wrights' preference for the unstable canard arrangement. One that I have not seen, but that strikes me as being at least as plausible as the others, is that the force vector on a canard surface points in the same direction as an intended maneuver. An aft tail, on the other hand, would push downward to increase the angle of attack of the wing, adding to the lift required of it to begin a climb.
Although the Wright brothers dazzled both America and Europe in 1908 with the superior maneuverability of their Flyers and with their own skills as pilots, their designs quickly became obsolete. Within less than 10 years the configuration that would remain standard until the Thirties, the strut-braced biplane with ailerons and an empennage, providing both stability and control, mounted at the tail end of a long fuselage, supplanted the short-coupled Wright canards. It in turn would be supplanted by the art-tailed monoplane — the very configuration originally proposed by Cayley and Pénaud.
The comparative ease with which a tractor monoplane, provided that its center of gravity be at or ahead of the quarter-chord point of the wing, can be made to fly regardless of poor rigging or unsuitable proportions of surface areas, suggests that it is a naturally advantageous configuration and that experimenters using it might have flown around 1900, even though they may have been inferior to the Wright brothers in genius and application.
There is some evidence that a tractor monoplane built by an engineer named Clément Ader may have made a brief flight in France in 1897. It was not, however, genuinely controllable. It appears also that a German-born American, Gustave Whitehead, may have gotten aloft in a tractor monoplane in Connecticut in 1901. Many witnesses testified to his flights, and a replica of his airplane has recently proved not only airworthy and controllable but also quite stable. There are various others for whom some sort of claim could be made.
The fact that modern re-creations of old designs can be made to fly does not prove by any means, however, that the originals did so. Their powerplants are usually different. In weighing claims of pre-Wright flight, it's well to remember that while the Wright airplane had miraculously efficient propellers and was quite light and aerodynamically fairly sophisticated, especially in having wings of high aspect ratio, it had a wretched engine. A less aerodynamically efficient airplane having a more powerful engine might also have flown. The Ader and Whitehead craft had primitive propellers and inferior wing designs; but their engines were more powerful.
Much rhetorical blood has been spilled over the question of who flew first, but it is really an inconsequential one. We ask not which horse's nose is first out of the gate, but which is ahead at the end of the race. Besides, it's not possible to define precisely the threshold of "powered flight." Whether a hop by Ader's uncontrollable Avion, or by Whitehead's Model 21 (which reportedly ended up colliding with the side of a building), actually took place and, if it did, whether it was truly a "flight," no one can say today.
Pre-Wright activities have been so distorted by the lenses of chauvinism, of litigiousness (brought about, misguidedly, by the Wrights themselves), and by a certain mania for heaping glory upon the Wright brothers (our boys!) to the exclusion of all others, that no conclusive historical record any more exists. It is even a matter of debate whether Orville's first flight of December 17th, the one in the famous photograph, really ought to be called a flight, or whether the true first flight was the last one of that day, when the Flyer traveled 850 feet through the air, with Wilbur at the controls, remaining aloft and under control for a full minute. It doesn't matter. The Wright brothers — and Ader and Lilienthal and Whitehead and Maxim and Langley and the rest — were great pioneers. We owe gratitude and admiration to them all.