The Airplane - Jay Spenser [65]
Germany’s flying man had controlled his gliders by flailing his legs and upper body in the direction he wanted to go. The Wrights knew that in scientific terms what Lilienthal was doing was shifting the position of the glider’s center of gravity relative to its center of lift. These were the respective points where aggregate physical forces—gravity and aerodynamic lift—acted on his glider, the former as a lever and the latter as a fulcrum.
When the center of gravity overlapped with the center of lift, Lilienthal’s glider was in balance and flew straight. But when Germany’s airman threw his legs to the right, the center of gravity shifted in that direction and the wing dipped into a turn. With lift’s upward push now to the left of the center of mass, the vehicle naturally fell off to that side.
To arrest this turn, all Lilienthal had to do was shift his weight the other way. And to lower the nose, he had but to throw his body and legs forward, placing the center of gravity ahead of the center of lift. It was a simple means of control that anyone could intuitively understand.
The Wrights understood it, but they also saw the meaning of Lilienthal’s death. That tragedy’s stark lesson was that this system of control did not suffice even for a small single-person glider. If flight was ever to be practical, a better method was needed, one that could be scaled up along with the machine itself. As Wilbur wrote in the summer of 1899, the “problem of equilibrium constituted the problem of flight itself.”7
Otto Lilienthal controlled his gliders by shifting his weight to change the craft’s center of gravity.
National Air and Space Museum, Smithsonian Institution
But what should this alternative mechanism be? English engineer Francis Wenham, whose work the Wrights knew and admired, provided a clue. Where others looked to a ship-style rudder for control, Wenham had said in 1866 that turns in flight should be accomplished by generating more lift on one of an aircraft’s wings than on the other.
Wenham based this insight on his observation of birds. Although the exact mechanism was unclear, he saw that they controlled their direction of flight primarily with their wings. Rudders were fine for turning ships, he believed, but to turn an aircraft one should look to the wings. It was prescient advice. So closely would Wilbur and Orville follow it that their initial gliders had no tails at all.
Ironically, just as these Ohio brothers took up flight’s challenges in 1899, another dreamer died as a result of his gliding experiments. Working in Scotland, British pioneer Percy Pilcher had built several different designs and was on the verge of testing a powered hang glider when he succumbed to injuries sustained in a crash. He was thirty-three years old.
The world was awash with ideas about flight. These came from all quarters and struck harmonic chords on emotional as well as cerebral levels.
Take Louis Mouillard, a Frenchman living in Algeria who studied birds and made a few gliding experiments in the 1860s and 1870s. In his influential 1881 book L’Empire de l’Air, Mouillard advocated gliding as the path to learning. When Wilbur wrote to the Smithsonian Institution in May 1899 requesting information about flight, he received an English translation of this work that the Smithsonian had published in 1893.
Writing passionately and poetically, Mouillard—whose own gliding experiments were insignificant—spoke to the soul as much as the mind. His words fueled the Wrights’ growing desire to build and fly gliders even if all it amounted to was a bit of fun. But the Frenchman himself predicted it would be more than that.
“If there be a domineering, tyrant thought,” Mouillard wrote, “it is the conception that the problem of flight may be solved by man. When once this idea has invaded the brain, it possesses it exclusively. It is then a haunting thought, a waking nightmare, impossible