The Wright Brothers

by Fred C. Kelly

Though their interest did not lag, the Wrights did nothing more for some time about kite experiments, except to seek information in regard to wind velocity in different parts of the country. They wrote to the Weather Bureau at Washington, in December, 1899, and Willis Moore, chief of that Bureau, sent them a number of government bulletins that included statistics on wind velocities at various places. They looked these over, but at that time made no further investigation of any of the places mentioned.

THE FIRST CAMP AT KITTY HAWK. Top: The 1900 camp. Bottom: Kitty Hawk Bay as seen from the 1900 camp.

In May, 1900, Wilbur Wright wrote a letter to Octave Chanute, living in Chicago, who had written Progress in Flying Machines. Though Chanute was better known in engineering circles by his work for certain western railroads, as well as for having built the Kansas City bridge and the Chicago stockyards, his book, a reprint of his articles published from 1891 to 1893, had made him probably the best authority on the history of aeronautics. Thinking Chanute would be interested, Wilbur told him in his letter of a plan he had for experimenting with a man-carrying kite by means of which, Wilbur thought, one would be able to get hours of practice in operating a machine in the air. He proposed the use of a high tower from the top of which a cable would lead to the man-carrying kite. He described to Chanute, in his letter, the system of control to be used in the kite—the warping of wings for lateral control, and the shifting of the upper surface backward and forward for longitudinal control—the same system used in the five-foot kite tested the previous August. Then he asked Chanute if he had any information as to locations where winds suitable for carrying on such experiments might be found. (This letter from Wilbur marked the beginning of an acquaintance and correspondence with Chanute that lasted for a number of years.) Chanute suggested San Diego, California, and St. James City (Pine Island), Florida, to be considered because of the steady sea breezes. But, on the other hand, he pointed out that, since those places were deficient in sand hills, perhaps even better locations could be found on the Atlantic coast of South Carolina or Georgia.

THE 1902 GLIDER. The Wrights are testing the efficiency of the 1902 glider by flying it as a kite—September 19, 1902.

When the rush of the spring trade in bicycles began to subside, giving them more time for other interests, the Wrights again took up with enthusiasm the study of equilibrium. Each day they proposed and discussed new devices. Orville thought the shifting of the upper surface backward and forward over the lower one, for longitudinal equilibrium, though successful in their kite, would not be practical for a man-carrying glider, which would start and land on the ground. He suggested that the wing surfaces be fixed one above the other, and that an elevator be placed some distance in front of the wings, instead of at the rear. In this position there would be less danger of the elevator touching the ground in starting; and if from any cause the elevator were disabled it would be discovered before the machine got into the air. Wilbur then proposed that, since curved surfaces were more efficient than flat planes, the front rudder, or elevator, should be made flexible. Then it could be bent to present a concave surface on whichever side a pressure was desired, but would be flat when moving edgewise through the air.

The Wrights did not at first think an elevator in front would provide inherent stability—that is, it would not give the machine the desired tendency to restore its own balance just from the arrangement of its fixed parts. But Wilbur shortly afterward developed a theory that led him to believe the machine would have that quality.

Having read that the center of pressure moves toward the front edge of the wings whenever the wings are turned more nearly horizontal in flight, he thought inherent longitudinal stability could be obtained if the front elevator were set at a negative angle—that is, with its front edge lower than its rear edge. With such an arrangement of wings and elevator, every time the wings became more nearly horizontal in flight and met the air at a smaller angle on their under sides, the elevator would meet the air at a greater angle on its upper side. So, he reasoned, whenever, by becoming more nearly horizontal, the wings caused the center of pressure to move forward, tending to turn the machine upward in front, the front elevator would receive a greater downward pressure on its upper side and so counteract the disturbing pressure on the wings.

Actual tests later proved that the negative angle of the front elevator did not provide the inherent stability expected. The explanation was that the center of pressure on cambered wings traveled in the opposite direction from that which Wilbur’s reading had led him to expect. The Wrights later were to discover that Wilbur’s reasoning was correct; but because the travel of the center of pressure was rearward instead of forward the elevator had to be set at a positive instead of at a negative angle.