The next step was a six-foot (1.8m) wind tunnel built in their shop which they used to test 200 miniature wings of many shapes and airfoil section curves, followed by detailed tests on 38 of them. This crude but effective device allowed them study the relationship of lift and drag and accurately calculate the performance of each wing. The tests yielded previously unknown data and showed that the poor lift of the 1900 and 1901 gliders was entirely due to an incorrect value of the Smeaton coefficient. The curvature (camber) of the upper wing surface and the aspect ratio (wingspan divided by the width, or chord, of the wing) were both wrong.
The Wrights designed their third glider making the airfoil flatter by reducing the camber (the depth of the wing's curvature divided by its chord) and more than doubling the aspect ratio from 3 to 6.5. (The wingspan increased to 32 ft from 22 ft with only a small increase in wing area). They also 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 yaw (turn) in the opposite direction to turn. They added a tail with twin fixed vertical stabilizers and this was so effective that it introduced a new problem. When the pilot levelled off from a turn, the glider sometimes persisted into a tighter turn and would slide, sideways, toward the lower wing, into the ground.
The brothers then replaced the vertical stabilizers with a single hinged, steerable rear rudder connecting it to the pilot's warping "cradle", so the pilot could simultaneously control wing-warping and rudder deflection. They had discovered the true purpose of the rudder. It did not change the direction of flight (as a rudder does on a boat), but was used to aim the aircraft during banking turns and when levelling off from turns and wind disturbances. The change in direction was made by wing-warping (and later ailerons) to control the roll.
At the Kill Devil Hills, between September 19 and October 24, 1902, they made more than 700 glides, the longest lasting 26 seconds and covering 622.5 feet (189.7 m). They were ready to build a powered flying machine.
They finally had true control for each axis of motion:- roll (wing warping), pitch (dive or climb - forward elevators) and yaw (left or right - rear rudder). On March 23, 1903, the Wrights applied for a patent for three axis control of a "Flying Machine", based on their successful 1902 glider.
The Wrights could not find a sufficiently lightweight engine for their Wright Flyer so their shop mechanic, Charlie Taylor, built a four cylinder engine in just six weeks, making the engine block from cast aluminum, unusual at the time as the process for extracting the metal at a reasonable cost had only recently been invented. (In 1889, aluminum production from Hall's plant, coincidentally at Oberlin, Ohio, was 385 pounds (175 kilograms) the cost was $0.65 per pound).In 1903 the brothers used data from more wind tunnel tests to design their 8 ft long propellers and carved them from three laminations of glued spruce. Two propellers were mounted behind the wings to act as pushers. They were contra-rotating to cancel torque and connected to the engine by automobile chains.
Gliders Wingspan Wing area Length weight
1900 17 ft 6 in 165 sq ft 11 ft 6 in 52 lb
1901 22 ft 290 sq ft 14 ft 98 lb
1902 32 ft 1 in 305 sq ft 17 ft 112 lb
Flyer 40 ft 4 in 510 sq ft 21 ft 605 lb
Aspect ratio (Wing span divided by wing cord).
1900 = 3.5
1901 = 3.0
1902 = 6.5
Flyer = 6.1
Flyer engine;- 4-cylinder, 12 horsepower (8.9 kW), weight 152 lbs (69 kg).
In their camp at Kill Devil Hills, Orville and Wilbur were delayed for weeks by broken propeller shafts but finally flew under power on December 17, 1903. They each made two flights into a freezing headwind gusting to 27 miles per hour (43 km/h). The first flight, by Orville covered 120 feet in 12 seconds, at a speed of only 6.8 miles per hour over the ground (because of the headwind). The next two flights covered approximately 175 and 200 feet at an altitude of about 10 feet above the ground. Unfortunately, the Flyer was flipped over by wind gusts and destroyed.
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Flight
Non-FictionThe Orville and Wilbur Wright flew under power in 1903. The first flight travelled only 120 feet but Wilbur flew 24.5 miles in 38 minutes in August 1904. More powerful aircraft engines were developed during WW-1 but airframes were too fragile for...
