The Airplane - Jay Spenser [70]
The lack of lateral and longitudinal stability meant that Wright pilots would have to be on their toes, actively controlling their mounts every instant while aloft. But this did not bother them for an instant. After all, bicycles had to be controlled all the time or their riders were in for a spill, yet nobody had trouble riding them. And with flights generally so brief (in those early days, at least), there was no time for pilots to become fatigued, so what did it matter?
Octave Chanute never understood or trusted the Wrights’ approach. He felt airplanes should be inherently stable for overall safety. So did the Europeans, who from the outset sought to build intrinsically stable flying machines. But stability fights against controllability, and for the Wrights controllability was the secret to flying.
Wing warping now worked and all seemed well. Gliding into the wind, Wilbur even demonstrated an S-turn, bringing the 1902 Glider broadside to the wind first one way and then the other, an unheard-of feat for a glider. But as testing continued, control instability again cropped up, and this time it was worse. In fact, in Orville’s own words, it was “absolutely dangerous.”9
As before, the positively warped wings would suddenly drop with no warning, and the glider, slewing violently, would fall sideways “as a sledge slides downhill or a ball rolls down an inclined plane, the speed increasing in an accelerated ratio,” as Wilbur described it.10
They had figured out what was going on with wing warping the previous year. Now they saw that the vertical stabilizer was aggravating the issue rather than helping. In Orville’s words, the tail “caused one wing to be checked and the other to be speeded up.”11
By resisting sideways motion, this fixed tail was aerodynamically preventing the glider from yawing and instead whipped it into a violent sideslip. Out of control, the glider would spin down around its low wing, invariably gouging a circular trough with its wingtip.
This signature in the sand led the Wrights—who just weeks before had dug a well for their camp—to name this sobering phenomenon well digging. There were no injuries from these crashes, but they kept the brothers busy with repairs.
On the evening of October 2, Wilbur went to bed early, as was his habit. Orville typically puttered around and read before finally turning out the lantern. This night he lay on his cot, listening to the mingled melody of crickets and surf. Sleep defeated him because he had drunk too much coffee.
As he lay awake, the younger Wright kept replaying in his mind their glider’s odd behavior. He traced mentally the different forces coming into play. Suddenly the solution came in an intuitive flash: replace the fixed vertical stabilizer with a movable rudder. During a turn, this rudder would deflect to the side of the low wing, pivoting the glider so that it tracked properly through the turn. This control input from the rear would also push the high wings around, overcoming the higher drag on that side of the glider.
The brothers made this change, wiring the rudder into the warping mechanism so that it too was actuated by the hip cradle. From now on, the rudder would automatically deflect when wing warping was commanded.
The Wright 1902 Glider made between seven hundred and eight hundred glides following modification with a movable rudder. Not once did Wilbur or Orville encounter further difficulties in control. In all, they would log nearly a thousand flights at Kill Devil Hill during September and October, making it by far the most productive of their three stays to date in North Carolina.
Here was history’s first fully controllable aircraft (lacking power, it was not an airplane). Never before had any man-made device flown with control around all three axes.
Flights of 500 feet (150 meters) were common, and some exceeded 600 feet (180