According to Lilienthal's tables, the pressure from the wind on the flat plate should equal the pressure-or lift-on the airfoil set at a 5-degree angle to the wind. Thus the wheel should remain stationary. But when the Wrights carried out their experiment, pedaling through the streets of Dayton, the pressure on the plate was higher than the lift on the airfoil, and the wheel turned toward the plate. Lilienthal was wrong.
To find the most efficient shape for the wings of their plane, the brothers next needed to perform more systematic tests. Their modified bicycle couldn't provide the precision they wanted-after all, they would be staking their lives on the accuracy of their data. So they built a wind tunnel, the first from which anyone obtained any useful data.
And so, of course, has Hyde. His wind tunnel, a rectangular wooden box, is identical to the Wrights' original: 6 feet long, 16 inches high. An electric fan at one end of the box pushes a steady stream of air at 27 miles per hour toward a delicate balance, made from hacksaw blades and bicycle spokes, positioned at the opposite end of the tunnel.
The Wrights suspended various airfoils on one side of the balance, and a standard flat plate on the other. The flat plate served as a reference, much as it had on their bicycle experiment, enabling the Wrights to calibrate a simple gauge that they attached to the balance. With this arrangement they methodically tested more than 200 airfoils, producing remarkably accurate data on lift and determining the ideal wing shape for their plane. In the attic of their Dayton workshop, they were laying the experimental groundwork for the science of aeronautics.
"We're discovering just how brilliant these two people were in solving complex problems," says Kevin Kochersberger, a mechanical engineer from the Rochester Institute of Technology. "It was their redesign and retesting year after year that allowed them to get to the level where they could solve the most complex problem-powered flight."
With the data from their wind tunnel tests the Wrights proceeded to build what is probably the second most important plane in the world, their 1902 glider. They had honed all the control mechanisms. A moveable rudder on the tail directed the plane's horizontal motion, or yaw. An elevator in front-essentially a small wing-could be angled up or down to change altitude. By shifting his hips left or right in a cradle attached to the lower wing, the pilot pulled cables that twisted one wing up and the other down, sending the plane into a turn. That summer, the new glider's performance at Kitty Hawk surpassed the brothers' expectations. Wilbur's best flight covered just over 622 feet and lasted for 26 seconds.