The Wright Brothers

by Fred C. Kelly

Almost as soon as they began their trials of the glider, the brothers got another surprise. According to the Lilienthal tables of air pressures, their machine of 165 square feet needed a wind of only from seventeen to twenty-one miles an hour to support it as a kite with a pilot aboard. But they found that much stronger winds were needed to lift it. Since suitable winds would not be plentiful, their plan of practicing by the hour aboard the glider while flying it as a kite would have to be postponed. Instead, they flew it as a kite, loaded with about fifty pounds of chain, but with no man aboard. They held it with two ropes, and operated the balancing system by cords from the ground. Though the results were promising, inspiring confidence in the system of maintaining equilibrium, the brothers knew that only by actual gliding experience could they confirm what the kite experiments had indicated as being true.

One thing that puzzled them was that the machine appeared to be greatly deficient in lifting power as compared with calculated lift of curved surfaces of its size. In wondering what might be the cause of this wide discrepancy between expected and actual lifts, the Wrights considered the possibility that it might be because the curvature of the wings was less than that used by Lilienthal. Or could it be that the cloth covering was too porous and permitted some of the lifting power of the wind to be lost? They wondered, too, if the Lilienthal tables they had followed, relating to air pressure on wing surfaces, could be in error.

They next determined to try gliding on the side of a hill. That meant toting their machine four miles south of their camp to a great sand dune about one hundred feet high, called Kill Devil Hill. On their first day at the hill, the wind was about twenty-five miles an hour. As they lacked previous experience at gliding they decided to wait for less of a blow for their first attempt. The next day the wind had subsided to fourteen miles an hour, and they made about a dozen glides. “Bill” Tate was there and assisted them.

In making these glides, the machine was usually only two or three feet from the soft, sandy ground, and though the brothers repeatedly made landings while moving at a speed of twenty miles an hour, neither operator nor machine was harmed. The slope of the hill toward the northeast was about 9½ degrees, or a drop of approximately one foot in six. After moving at a rate of about twenty-five to thirty miles an hour with reference to the wind, or ten to fifteen miles over the ground, the machine, while keeping its course parallel to the slope, increased its speed, thus indicating that it could glide on a slope less steep.

Their control of the machine was even better than they had dared to expect. They got quick response to the slightest movement of the front elevator, which promised to be satisfactory in maintaining fore and aft balance. At first, they fastened the warping mechanism, to make it inoperable, and had only the elevator to manipulate, for they feared that, inexperienced as they were, if they tried to use both, then they might be unsuccessful with either. But even without the use of the warping mechanism it was possible to make glides of from five to ten seconds before the sidewise tilt of the machine forced a landing. Before making the last three or four flights the Wrights loosened the warping wires to permit the sidewise control to be used.

When these experiments of 1900 ended, instead of the hours of practice in the air the Wrights had hoped to have, they had flown the machine as a kite with a man aboard barely ten minutes, and had had only two minutes of actual gliding.

Now that the experiments for that year were ended and they had no further use for the glider, the brothers weighted the machine with sand and left it on the hill. When “Bill” Tate saw that they were through with the glider he asked if he might have it, and they gladly gave it to him. Mrs. Tate used the sateen that covered the wings to make dresses for her two small daughters. She noted that it appeared to be unusually good fabric, more closely woven and better than she had seen in the stores. Some of her neighbors, when they saw the dresses she made of it, remarked that it seemed too bad to use such excellent material on a kite.

Though the amount of practice was less than they had expected, all the Wrights had learned in that season of 1900 seemed to confirm the correctness of certain opinions held at the beginning. Their method of warping or twisting the wings to maintain lateral balance was better than dependence on either the dihedral angle or shifting the weight of the operator; better than any method yet tried. And their front elevator had been highly satisfactory as a means for directing the machine up and down. Before leaving Kitty Hawk they decided that their next experiments would be with a glider large enough to be flown as a kite, with an operator aboard, in winds ordinarily to be counted on.

When the brothers set to work on their glider for the experiments of 1901, they decided to make it of the same general design as the first one, and with the same system of control. But they carried out their plan to give it considerably more area, to provide greater lifting power. Another change they made was to increase the curvature of the wings to conform to the shape on which Lilienthal had based his tables of air pressures. It had wings of about seven-foot chord (the straight line distance between the front and rear edges) with a total span of twenty-two feet, and weighed ninety-eight pounds. After a section twenty inches wide had been removed from the middle of the lower wing, and the rear corners of the wings rounded off, the total lifting area was 290 square feet, as compared with 165 in the previous glider. The front elevator, with its rear edge about two and one half feet away from the front edge of the wings, had a four-and-one-half foot chord and an area of eighteen square feet.

This was a much larger machine than anyone had ever tried to fly. The Wrights knew it could not be controlled simply by shifting the pilot’s weight, as others had done, but they had faith in their own operable front elevator and believed they could manage it. If their calculations were correct, it would be supported in a wind of seventeen miles an hour, with the wing surfaces at an “angle of incidence” of only three degrees. (“Angle of incidence,” now more often called “angle of attack,” has been defined as the angle at which the plane presents itself to the air in advancing against it.)