The following article, Wrightophilia, is from the December 2003 print issue.
The story of the achievement of powered flight by the Wright brothers, which in its bare outline is familiar to everyone, grows more interesting to me as I delve more deeply into it. Orville and Wilbur Wright, as indistinguishable at first glance as Tweedledum and Tweedledee, become distinct. The stages in the development of their design thinking and their airplane come into focus. Most curiously, however, I become aware of the paradoxical way in which a flawed design — an aeronautical Ugly Duckling — succeeded in spite of itself.
An odd thing about the Wright Flyer is how few other airplanes have ever resembled it. Within a few years its principal defining characteristics — canard configuration and wing warping — would be discarded in favor of the arrangement now termed "conventional." Moreover, what we now consider the conventional configuration did not evolve subsequent to the Wright brothers; it actually antedated them by more than 100 years.
A prescient English experimenter, Thomas Cayley, had amply documented the characteristics of an airplane with monoplane wings, dihedral, and an empennage consisting of vertical and horizontal surfaces at some distance behind the wing. Cayley's insights, formed around 1800, were monumental; it's odd that his name is not better known. He discovered the stabilizing effect of dihedral and recognized the desirability of separating the function of propulsion from that of lifting. This subtle but fundamental idea had not even occurred to Mother Nature. It came at a time when no engine existed that approached the power-to-weight ratio needed for flight, but Cayley suggested that a suitable engine might be made by harnessing the combustion of "spirit of tar" (i.e. petroleum) with a cylinder and piston. A Cayley glider looks very much like a toy that a child of today might build with balsa wood and rice paper (or styrofoam and mylar, or whatever modem youth imagines to be suitable construction materials).
Around 1870, a Frenchman named Pénaud took Cayley's glider one step further. He provided it with a propeller, which he mounted on the tail and drove with a twisted rubber band. Pénaud also gave the first rational explanation of the stabilizing effect of an empennage. Except for the use of a pusher propeller-a comparatively minor deviation, and one that incidentally increases stability with Pénaud the definition of the standard configuration of a "normal" propeller-powered aircraft was complete. A picture of his remarkably modern-looking model can be seen here.
The Wright brothers were aware of Cayley and Pénaud, and also (very much so) of Otto Lilienthal, the German experimenter whose hang gliders used the "correct" tail-in-back configuration and whose book, Bird Flight as the Basis of Aeronautics, they studied obsessively. But they resisted the influence of their precursors, preferring to start with a clean slate.
The Wright Flyer descended from a series of gliders designed, built and tested by the brothers over a period of three years. I should emphasize at this point that the phrase "by the brothers" is one of a number of locutions (including constant references to the brothers in thought and action as "they," as though they were some sort of synchronized swimming team) that tend to obscure the fact that we are talking about two men, not one.
In fact, Wilbur, the elder by four years (he's the bald-headed one with the cap), was the brains and the driving ambition of the team, and the papers that document every stage of the evolution of the Flyer and its antecedents are largely from his hand. Orville (moustache, bowler) was not merely a superfluous appendage, however; the two worked symbiotically, with an almost telepathic coordination. Perhaps unjustly, Orville happened to be the one who made the first recorded powered flight.
The first Wright glider, flown initially as an unmanned kite in 1900, consisted of nothing more than an unadorned biplane "cell." It acquired a foreplane for pitch control in 1901 and an aft-mounted vertical stabilizer in 1902, at which point its configuration, but for engine and propellers, was that of the powered Flyer of 1903.
The point has often been made that whereas European experimenters were fixated upon the idea of stability, the Wright brothers, supposedly because of their familiarity with bicycles, attached less importance to stability and more to control. Now, from a modern perspective neither excludes the other; we expect airplanes to be both stable and controllable. But if they are to be one thing only, they must be controllable; the human pilot can go a long way to replace some missing stability. It was because of the importance they placed on control that the Wrights managed to outstrip their European competitors.