Historic Inventions

by Rupert Sargent Holland

These two brothers, scientifically minded, started a bicycle shop, and bade fair to become ordinarily prosperous citizens of Dayton, much like their neighbors. They were, however, deeply interested in news from the world of science and invention, and when they read in 1896 that Lilienthal had been killed by a fall from his glider they began to wonder what were the real difficulties that must be overcome in flying. Further reading awakened a deep interest in the problem of the airship, and they worked upon it, at first as a scientific pastime, but soon in all seriousness. They built models in their workshop, and experimented with them. Then, in 1900, Wilbur wrote to his father that he was going on a holiday to a place in North Carolina called Kitty Hawk, to try a glider.

The Wrights realized in 1900 that the only problem to be solved was that of equilibrium. Men had made aeroplanes that would support them in motion, and also engines that were light enough to drive the planes and carry their own weight and that of the aviator. But when the wind blew the aeroplane was as likely as not to capsize. Their study was how to keep the machine from turning over.

The air does not blow in regular currents. Instead, near the earth, it is continually tossing up and down, and often whirling about in rotary masses. There is constant atmospheric turmoil, and the question is how to maintain a balance in these currents that bear the machine. Put in technical form it is how to make the centre of gravity coincide with the centre of air-pressure.

The shifting of the air-currents means that the centre of air-pressure moves. The aeroplane is sailed at a slight angle to the direction in which it is heading, and the centre of air-pressure is on the forward surfaces of the machine. The wind strikes the front, but rarely touches the back of the plane, and so gains a great leverage that adds materially to its power to overturn the machine. As the wind veers continually it is easy to see the aviator’s difficulty in keeping track of this centre of pressure.

Both Lilienthal and Chanute had tried to balance by shifting their weight, but this was extremely exhausting, and often could not be done in time to meet the changing currents. The Wrights realized that a more automatic method of meeting these changes must be found, and they worked it out by shifting the rudder and the surfaces of the airship as it met the air-currents.

The earlier aviators had found that two planes, or “double-deckers,” gave the best results. The Wrights adopted this type, believing that it was the strongest form, and could be made more compact and be more easily managed than the single plane, or the many-winged type. They built their gliding-machine of cloth and spruce and steel wire. But instead of the aviator hanging below the wings, as in the other planes, he lay flat across the centre of the lower wing. A horizontal rudder extended in front of the plane instead of behind it. This not only guided the flight of the machine, but counterbalanced the changes of the centre of air-pressure. To steer, the wings were moved by cords controlled by the aviator’s body. They considered that the shiftings of the air were too rapid to be followed by conscious thought, and so their plan was to have a plane that would balance automatically, or by reflex action, as a bicycle is balanced.

Langley had adopted wings that slanted upward from the point at which they joined, copying the wings of a soaring buzzard. The Wrights doubted whether this was the best form for shifting weather, and built theirs more on the pattern of the gull’s wings, curving slightly at the tips. They were made of cloth, arched over ribs to imitate the curved surfaces of bird’s wings, and were fastened to two rectangular wooden frames, fixed one above the other by braces of wood and wire.

Their next step was to try to find some method by which they might keep their gliding-machine continuously in the air, so that they might gain an automatic balance. The old method of launching the plane from a hill gave little chance for a real test. Study taught them that birds are really aeroplanes, and that buzzards and hawks and gulls stay in the air by balancing on or sliding down rising currents of air. They looked for a place where there should be winds of proper strength to balance their machine for a considerable time as it slid downward, and decided to make their experiments at Kitty Hawk, North Carolina, on the stretch of sand-dunes that divided Albemarle Sound from the Atlantic Ocean. They calculated that their gliding-machine, with 165 square feet of surface, should be held up by a wind blowing twenty-one miles an hour. The machine was to be raised like a kite, with men holding ropes fastened to the end of each wing. When the ropes were freed the aviator would glide slowly to the ground, having time to test the principle of equilibrium. This plan would also do away with the former need of carrying the plane up to the top of a hill before each flight.

They found in practice that their plan of raising the plane like a kite was impracticable, and that the wind was not strong enough to support it at a proper angle. They had to glide from hills as others had done, but they discovered that their theory of steering and balancing by automatically shifting surfaces worked very much better than the old method of shifting the aviator’s weight.

In 1901 and 1902 the Wrights continued their gliding experiments at Kitty Hawk. Their new machines were much larger, and they added a vertical tail in order to secure better lateral balance. Sometimes the wind was strong enough to lift the aviator above the point from which he had started and hold him motionless in the air for half a minute. They made new tables of calculation for aerial flight, and found that a wind of eighteen miles an hour would keep their plane and its operator in the air.