Fig. 22.—Lilienthal Glider.
This, then, was Lilienthal’s plan; he would build a machine with wings and a tail, stand facing the wind as the storks had done, then seek to glide through the air in the manner of a soaring bird. The idea underlying his scheme was that he hoped, by a series of such gliding flights, to learn the adjusting movements he knew would be necessary to preserve his balance in the air. The gliding craft Lilienthal built, as illustrated in [Fig. 22], has become an historical machine. The framework of its wings and the supports of its tail were of willow, and the wings and tail, to give them their grip upon the air, were covered with a smoothly stretched fabric. Then the whole structure was braced and tightened; and though it weighed less than 50 lbs., it was strong enough to bear its operator though the air. Lilienthal could raise the apparatus upon his shoulders—passing his head through the aperture between the planes, which will be noted in the sketch—and walk or run forward; and to hold the machine, as he carried it thus, he gripped two wooden rods. The tail was flexible, being allowed an automatic movement, thus giving the craft a certain natural stability. The main wings had a span of 24 feet, and the machine measured 18 feet from front to tail. The wings were cambered, according to the curve Lilienthal had decided most efficient, and contained about 180 square feet of lifting surface. In giving them this area, Lilienthal was relying upon experiments he had made; these showed that, as his machine glided through the air, each square foot of its surface should bear a weight equal to about 1 lb.
Although enthusiastic, Lilienthal was not impatient: he had the priceless gift of judgment, allied to common-sense. So, when he had his glider built, he made no wild nor dangerous tests. He contented himself, in fact, with a leap from a springboard no more than 3 feet high; and this height he increased gradually to 8 feet. By such humble beginnings, and without risking his life, he proved that his glider would sustain his weight in the air; or, to be more precise, that its wings would exercise a lift sufficient to permit him to glide rather than fall to the ground. So now he began more elaborate tests, seeking hills which had gently-sloping sides, so that he might glide down them. But with many the difficulty was this: the winds near the surface, being broken and disturbed, blew fitfully and in gusts, while what Lilienthal needed was a steady, uniform wind. At length he found favourable conditions at some gravel-pits at Südende; and here, on the brink of a pit, he built a shed and housed his gliders.
PLATE II.—SANTOS-DUMONT’S FIRST FLIGHTS.
Here, actually in the air, and with its pilot clearly visible at the controls, is seen the craft in which—at Bagatelle in 1906—the airman flew a distance of 230 yards.
Now, patient and assiduous, he began to teach himself the art of aerial balance. Raising his wings to his shoulders he would face the wind—which in his first tests he did not care to be blowing at more than ten or fifteen miles an hour. Then, running against the wind to increase the pressure beneath his wings, he would raise his legs and begin to glide, moving forward and at the same time downward. How he appeared when in flight is indicated by Fig. 23.
