page_title: Wright brothers
section_title: 1902
hierarchical_section_title: Wright brothers / Flights / Gliders / 1902
caption_attribution_description: Wilbur Wright piloting 1902 glider near Kitty Hawk, N.C.
context_page_description: The Wright brothers—Orville and Wilbur —were two American aviation pioneers generally credited with inventing, building, and flying the world's first successful motor-operated airplane. They made the first controlled, sustained flight of a powered, heavier-than-air aircraft with the Wright Flyer on December 17, 1903, 4 mi south of Kitty Hawk, North Carolina. In 1904–05, the brothers developed their flying machine to make longer-running and more aerodynamic flights with the Wright Flyer II, followed by the first truly practical fixed-wing aircraft, the Wright Flyer III. The Wright brothers were also the first to invent aircraft controls that made fixed-wing powered flight possible.
  The brothers' breakthrough was their creation of a three-axis control system, which enabled the pilot to steer the aircraft effectively and to maintain its equilibrium. This method remains standard on fixed-wing aircraft of all kinds. From the beginning of their aeronautical work, the Wright brothers focused on developing a reliable method of pilot control as the key to solving "the flying problem".
context_section_description: Lilienthal had made "whirling arm" tests on only a few wing shapes, and the Wrights mistakenly assumed the data would apply to their wings, which had a different shape. The Wrights took a huge step forward and made basic wind tunnel tests on 200 wings of many shapes and airfoil curves, followed by detailed tests on 38 of them. The tests, according to biographer Fred Howard, "were the most crucial and fruitful aeronautical experiments ever conducted in so short a time with so few materials and at so little expense". An important discovery was the benefit of longer narrower wings: in aeronautical terms, wings with a larger aspect ratio (wingspan divided by chord—the wing's front-to-back dimension). Such shapes offered much better lift-to-drag ratio than the broader wings the brothers had tried so far.
  With this knowledge, and a more accurate Smeaton number, the Wrights designed their 1902 glider. Using another crucial discovery from the wind tunnel, they made the airfoil flatter, reducing the camber (the depth of the wing's curvature divided by its chord). The 1901 wings had significantly greater curvature, a highly inefficient feature the Wrights copied directly from Lilienthal. Fully confident in their new wind tunnel results, the Wrights discarded Lilienthal's data, now basing their designs on their own calculations.
  With characteristic caution, the brothers first flew the 1902 glider as an unmanned kite, as they had done with their two previous versions. Rewarding their wind tunnel work, the glider produced the expected lift. It also had a new structural feature: a fixed, rear vertical rudder, which the brothers hoped would eliminate turning problems.
  By 1902 they realized that wing-warping created "differential drag" at the wingtips. Greater lift at one end of the wing also increased drag, which slowed that end of the wing, making the glider swivel—or "yaw"—so the nose pointed away from the turn. That was how the tailless 1901 glider behaved.
  The improved wing design enabled consistently longer glides, and the rear rudder prevented adverse yaw—so effectively that it introduced a new problem. Sometimes when the pilot attempted to level off from a turn, the glider failed to respond to corrective wing-warping and persisted into a tighter turn. The glider would slide toward the lower wing, which hit the ground, spinning the aircraft around. The Wrights called this "well digging".
  Orville apparently visualized that the fixed rudder resisted the effect of corrective wing-warping when attempting to level off from a turn. He wrote in his diary that on the night of October 2, "I studied out a new vertical rudder". The brothers then decided to make the rear rudder movable to solve the problem. They hinged the rudder and connected it to the pilot's warping "cradle", so a single movement by the pilot simultaneously controlled wing-warping and rudder deflection. Tests while gliding proved that the trailing edge of the rudder should be turned away from whichever end of the wings had more drag (and lift) due to warping. The opposing pressure produced by turning the rudder enabled corrective wing-warping to reliably restore level flight after a turn or a wind disturbance. Furthermore, when the glider banked into a turn, rudder pressure overcame the effect of differential drag and pointed the nose of the aircraft in the direction of the turn, eliminating adverse yaw.
  In short, the Wrights discovered the true purpose of the movable vertical rudder. Its role was not to change the direction of flight (as a rudder does in sailing), but rather, to aim or align the aircraft correctly during banking turns and when leveling off from turns and wind disturbances. The actual turn—the change in direction—was done with roll control using wing-warping. The principles remained the same when ailerons superseded wing-warping.
  With their new method the Wrights achieved true control in turns for the first time on October 8, 1902, a major milestone. From September 19 to October 24 they made between 700 and 1,000 glides, the longest lasting 26 seconds and
caption: Wilbur Wright pilots the 1902 glider over the Kill Devil Hills, October 10, 1902. The single rear rudder is steerable; it replaced the original fixed double rudder.
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