Learning to fly in the U.S. Army

by E. N. Fales

Lillienthal was the first man to accomplish successful flights through the air by the use of artificial wing surfaces. After many years of experiment and study of soaring birds he constructed rigid wings which he held to his shoulders and which, after he had gained considerable velocity by running forward downhill, would catch the air and lift his weight completely off the ground. The wings were arched, for he observed this was the case in all birds; flat wings proved useless in flight, and suggested a reason for the failure of previous experimenters. To these rigid wings Lillienthal fastened a rigid tail; the wings and the tail comprised his “glider.” There were no control levers and the only way the operator could steer was to shift the balance by swinging his legs one way or the other. Lillienthal constructed an artificial hill for his gliding so that he could coast downward for some distance without striking the ground and he was able to accomplish many glides of a couple of hundred yards in length.

Chanute (Chicago, 1896).—Chanute’s experiments in gliding were quite similar to Lillienthal’s and were made on the sand dunes along Lake Michigan outside of Chicago. His apparatus was more strongly constructed, being of trussed biplane type, a construction suggested to him by his experience in bridge building, and one which persists today as the basis of strength in our present military biplanes.

The Wright Brothers, 1901.—Lillienthal was killed in a glide, having lost control of his apparatus while some distance above the ground. The Wright brothers read of his death and commenced thinking over the whole problem. Lillienthal’s method of balancing his large apparatus by the mere effect of swinging his legs appeared to them as a very inadequate means of control. They came to the conclusion that the immediate problem in artificial flight was the problem of stability, which they felt should be solved by an entirely different means than that employed by Lillienthal and Chanute. The work already done had demonstrated without question that support in the air had been established; with the addition of controllability the Wrights looked forward to doing something worth while in the way of artificial flight.

To improve Lillienthal’s method of shifting the weight, they conceived the idea of leaving the pilot in an immovable position in the glider, and instead of obliging him to shift his weight this way and that, they proposed to manipulate the surfaces of the wings themselves by means of levers under the pilot’s control, so that the same result of balancing could be obtained by quite a different and superior method.

They set out, therefore, deliberately to solve the whole question of airplane stability. There was the fore and aft or horizontal stability, for which Lillienthal had swung his legs forward and backward; there was in addition the sidewise or lateral stability for which Lillienthal had swung his legs to left and right. The fundamental requirements to be met were that during flight the glider should be kept in its proper attitude without diving or rearing up, and without rolling into an attitude where one wing tip was higher than the other, i.e., the machine was to be kept level in both directions.

First Wright glider.	Final Wright glider.
With front elevator, shown flying empty as a kite.	With rudder and elevator. Note right wing warped downward to raise right wing tip.	A successful downhill glide. Pilot lies prone on bottom wing.

Fig. 4.

Fore and Aft Control.—After some preliminary trials the Wrights found that the fore and aft balance could be controlled by an elevator or horizontal rudder, supported on outriggers on the front of the airplane, and operated by a lever. If the pilot found the glider pitching too much downward, and tending toward a dive, he would tilt the elevator upward by moving the lever, thus turning the glider back into its proper attitude. This elevator in modern machines is back of the airplane, a better place for it than was chosen by the Wrights. It may be said that their chief reason for first putting it in front was that they could see it there and observe its effect. They soon realized that the rear location gave easier control, and they acted accordingly.

Lateral Control.—After satisfying themselves regarding fore and aft control, the Wrights took up lateral control. Their problem was to devise a means for keeping the span of the wings level so that when for any reason one wing tip should sink lower than the other, it could be at once raised back to its proper position. Lillienthal had tried to do this by swinging his legs toward the high side; the shifted weight restoring the position. The Wrights, to obviate this inadequate method, bethought themselves to restore equilibrium by means of the wind itself rather than by gravity. They observed an interesting maneuver employed by a pigeon which seemed to secure its lateral balance in exactly the way they wanted; this bird was seen to give its two wings each a different angle of attack, whereat one wing would lift more forcibly than the other, thereby rotating the bird bodily in any desired amount or direction about the line of flight as an axis. To copy this bird apparatus in a Wright glider, it was found sufficient to alter the angle of the wing tips only, leaving the chief part of the supporting surface in its original rigid position. In other words, the wing tips were to be warped; the one to present greater angle of attack, the other less angle, exactly as in the case of the pigeon. Suppose the airplane to develop a list to the left, the wing on that side sinking, the pilot was to increase the angle at the tip of this left-hand wing by moving the warping lever, and at the same time decrease the angle of the right-hand wing by the same lever. He was to hold this position until the airplane was righted and brought back to level position.