The Wright Brothers

by Fred C. Kelly

Since Lilienthal had already aroused the brothers’ admiration, they were especially interested in what he had done. With hundreds of short flights, he had had more flying practice than anyone else, even though he had been in the air a total of only five hours in five years. Lilienthal became the Wrights’ hero. They decided that he, by his experiments, had made more advance in the flying art than had anyone else up to that time—an opinion, it may be added, that they never changed.

Their reading now gave the Wrights a good idea of how earlier experimenters had attempted to solve the problem of equilibrium. Some experimenters had placed the center of gravity far below the wings, on the theory that the weight would seek to remain at the lowest point. But it had been proved that the wings would then oscillate about the center of gravity in a manner destructive to stability. Others had arranged the wings in the shape of a broad V, to form a dihedral angle, with the center low and the wing tips elevated. This, too, tended to make the machine oscillate from side to side except in calm air. Pénaud, in his models propelled by rubber bands, had used wings that formed a dihedral angle, and a rear stabilizer set with its forward edge lower than the rear edge. This produced inherent stability in both lateral and longitudinal directions. Lilienthal, Chanute, and some of the others had used the Pénaud system in their gliders, but in addition to that system they counted on shifting the weight of their bodies to help maintain equilibrium.

All this reading, while adding to their store of knowledge, also gave the Wrights much misinformation. One wrong idea they got was that men already knew how to design wings and propellers of such efficiency that motors then available could easily sustain the machine in the air; another, that the greatest problem was to maintain equilibrium. They also were misled into thinking that fore and aft control of a flying machine would be much more difficult than lateral control.

That neither Lilienthal nor any other experimenter had ever tried any more adequate method to insure lateral balance struck Orville as surprising. Why, he asked himself, wouldn’t it be possible for the operator to vary the inclination of sections of the wings at the tips and thus obtain force for restoring balance from the difference in the lifts of the two opposite wing tips? That seems today an obvious enough idea, but no one had ever done anything about it before. Orville had hit on a fundamental principle. (Indeed, this principle later became the basic claim of the original Wright patent, and the claim was sustained, as covering the idea of the aileron control, in all countries where the Wright patents were adjudicated.)

Orville made a rough sketch of a wing, showing a stationary section at the center, consisting of approximately one-third of the wing, measured from tip to tip, with two adjustable sections, one at either side. These sections were carried on shafts interconnected by cogs mounted on the center section and extending toward the wing tips. The movement of a lever attached to one of the shafts would cause one wing section to rotate in one direction while the other wing would turn in the opposite direction. Thus a greater lift could be obtained on whichever side it was needed.

The Wrights soon saw, however, that for two reasons this particular design did not provide a good structure for a gliding machine. First, with two-thirds of the entire weight of the machine and operator carried by the two shafts, the structure would be weak; and, second, with the ends of the wings free to turn about the shafts, there would not be enough rigidity for a machine that would have to be toted about.

Then one night, some five or six weeks later, Wilbur came home from the bicycle shop, to tell Orville enthusiastically of an idea he had hit upon. A customer had dropped in to buy an inner tube for a tire. Wilbur had taken the tube from the pasteboard box it came in and was toying with the box while talking to the customer. As he twisted the box he observed that though the vertical sides were rigid endwise, the top and bottom sides could be twisted to have different angles at the opposite ends. Why, he thought, couldn’t the wings of a gliding machine be warped from one end to the other in this same way? Thus the wings could be put at a greater angle at one side than at the other, without structural weakness. That plan seemed so satisfactory that the Wrights did not look for or consider any other method.

A few weeks later, in August, 1899, the brothers built a biplane kite, and Wilbur, with a group of small boys as spectators, flew it on a common at the edge of town. This kite had wing surfaces five feet from tip to tip by thirteen inches wide. The warping of these surfaces could be accomplished by the use of four cords reaching from the kite to the ground. Two of the cords were attached to the forward corners of the right wing tips, one to the upper and one to the lower; the other ends of the cords, at the ground, were tied to opposite ends of a short stick to be held in the operator’s hand. The cords tied to the left wing were arranged in the same way. With a stick in each hand, the operator could move the wings as he desired. The upper wing could be moved farther forward or farther backward than the lower wing, according to the direction in which the two sticks were simultaneously inclined, by movement of the wrists. By inclining the two sticks in opposite directions it was possible to draw one upper wing tip farther forward than the lower at that end, while at the other end of the kite the lower wing tip would be the one farther forward. This moving of the wing tips in opposite directions caused a twisting or warping of the wings. Then the wing at one end would be presented to the wind at a different angle from that at the other end. If one end of the kite started to sink, sidewise balance could be restored by exposing the wing at that end at a greater angle, thus getting more lift.

Balance from front to rear was to be maintained by inclining the two sticks in the operator’s hands in the same direction—to move the upper wing either forward or backward over the lower wing, to change the center of lift.

But in addition to this moving of the wings forward and backward, the Wrights added an “elevator” at the rear. It was held by a pair of wooden rods attached at right angles to the uprights that connected the wings. When the upper wing was pulled forward, to turn the kite upward in front, the elevator met the air at its top side and was pressed downward, which helped to turn the wings upward—as the rear elevator does on planes today.