page_title: Wright brothers
section_title: 1901
hierarchical_section_title: Wright brothers / Flights / Gliders / 1901
caption_attribution_description: English: Wilbur Wright in prone position on glider just after landing, its skid marks visible behind it and, in the foreground, skid marks from a previous landing; Kitty Hawk, North Carolina.
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: Hoping to improve lift, they built the 1901 glider with a much larger wing area and made dozens of flights in July and August for distances of 50 to 400 ft (15 to 122 m). The glider stalled a few times, but the parachute effect of the forward elevator allowed Wilbur to make a safe flat landing, instead of a nose-dive. These incidents wedded the Wrights even more strongly to the canard design, which they did not give up until 1910. The glider, however, delivered two major disappointments. It produced only about one-third the lift calculated and sometimes pointed opposite the intended direction of a turn—a problem later known as adverse yaw—when Wilbur used the wing-warping control. On the trip home a deeply dejected Wilbur remarked to Orville that man would not fly in a thousand years.
  The poor lift of the gliders led the Wrights to question the accuracy of Lilienthal's data, as well as the "Smeaton coefficient" of air pressure, a value which had been in use for over 100 years and was part of the accepted equation for lift.
  The Wrights used this equation to calculate the amount of lift that a wing would produce. Over the years a wide variety of values had been measured for the Smeaton coefficient; Chanute identified up to 50 of them. Wilbur knew that Langley, for example, had used a lower number than the traditional one. Intent on confirming the correct Smeaton value, Wilbur performed his own calculations using measurements collected during kite and free flights of the 1901 glider. His results correctly showed that the coefficient was very close to 0.0033 (similar to the number Langley used), not the traditional 0.0054, which would significantly exaggerate predicted lift.
  To learn whether errors actually existed in Lilienthal's data tables, the brothers used a bicycle for a new type of experiment. They made a model-size airfoil and a counter-acting flat plate, both according to dimensions Lilienthal had specified, and attached them to an extra bicycle wheel, which they mounted horizontally in front of the handlebars. Pedaling strenuously on a local street to create airflow over the apparatus, they observed that the third wheel rotated against the airfoil instead of remaining motionless as Lilienthal's formula predicted. The experiment confirmed their suspicion that either the standard Smeaton coefficient or Lilienthal's coefficients of lift and drag—or all of them—were in error.
  They then built a six-foot (1.8m) wind tunnel in their shop and between October and December 1901 conducted systematic tests on dozens of miniature wings. The "balances" they devised and mounted inside the tunnel to hold the wings looked crude, made of bicycle spokes and scrap metal, but were "as critical to the ultimate success of the Wright brothers as were the gliders." The devices allowed the brothers to balance lift against drag and accurately calculate the performance of each wing. They could also see which wings worked well as they looked through the viewing window in the top of the tunnel. The tests yielded a trove of valuable data never before known and showed that the poor lift of the 1900 and 1901 gliders was entirely due to an incorrect Smeaton value, and that Lilienthal's published data were fairly accurate for the tests he had done.
  Before the detailed wind tunnel tests, Wilbur traveled to Chicago at Chanute's invitation to give a lecture to the Western Society of Engineers on September 18, 1901. He presented a thorough report about the 1900–01 glider experiments and complemented his talk with a lantern slide show of photographs. Wilbur's speech was the first public account of the brothers' experiments. A report was published in the Journal of the society, which was then separately published as an offprint titled Some Aeronautical Experiments in a 300 copy edition.
caption: Wilbur just after landing the 1901 glider. Glider skid marks are visible behind it, and marks from a previous landing are seen in front; Kill Devil Hills, North Carolina.
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