In 1903 Orville and Wilbur Wright built the powered Wright Flyer I, using their preferred material for construction, spruce, a strong and lightweight wood, and Pride of the West muslin for surface coverings. They also designed and carved their own wooden propellers, and had a purpose-built gasoline engine fabricated in their bicycle shop. They thought propeller design would be a simple matter and intended to adapt data from shipbuilding. However, their library research disclosed no established formulas for either marine or air propellers, and they found themselves with no sure starting point. They discussed and argued the question, sometimes heatedly, until they concluded that an aeronautical propeller is essentially a wing rotating in the vertical plane. On that basis, they used data from more wind tunnel tests to design their propellers. The finished blades were just over eight feet long, made of three laminations of glued spruce. The Wrights decided on twin pusher propellers (counter-rotating to cancel torque), which would act on a greater quantity of air than a single relatively slow propeller and not disturb airflow over the leading edge of the wings.
Wilbur made a March 1903 entry in his notebook indicating the prototype propeller was 66% efficient. Modern wind tunnel tests on reproduction 1903 propellers show they were more than 75% efficient under the conditions of the first flights, and actually had a peak efficiency of 82%. This is a remarkable achievement, considering that modern wooden propellers have a maximum efficiency of 85%.
The Wrights wrote to several engine manufacturers, but none met their need for a sufficiently lightweight powerplant. They turned to their shop mechanic, Charlie Taylor, who built an engine in just six weeks in close consultation with the brothers. To keep the weight low enough, the engine block was cast from aluminum, a rare practice for the time. The Wright/Taylor engine was a primitive version of modern fuel-injection systems, having no carburetor or fuel pump. Gasoline was gravity-fed into the crankcase through a rubber tube from the fuel tank mounted on a wing strut.
The propeller drive chains, resembling those of bicycles, were actually supplied by a manufacturer of heavy-duty automobile chain-drives. The Flyer cost less than a thousand dollars, in contrast to more than $50,000 in government funds given to Samuel Langley for his man-carrying Great Aerodrome. The Flyer had a wingspan of 40.3 ft, weighed 605 lb and sported a 12 horsepower 180 lb engine.
In camp at Kill Devil Hills, they suffered weeks of delays caused by broken propeller shafts during engine tests. After the shafts were replaced (requiring two trips back to Dayton), Wilbur won a coin toss and made a three-second flight attempt on December 14, 1903, stalling after takeoff and causing minor damage to the Flyer. (Because December 13, 1903, was a Sunday, the brothers did not make any attempts that day, even though the weather was good.) In a message to their family, Wilbur referred to the trial as having "only partial success", stating "the power is ample, and but for a trifling error due to lack of experience with this machine and this method of starting, the machine would undoubtedly have flown beautifully." Following repairs, the Wrights finally took to the air on December 17, 1903, making two flights each from level ground into a freezing headwind gusting to 27 miles per hour (43 km/h). The first flight, by Orville, of 120 feet (37 m) in 12 seconds, at a speed of only 6.8 miles per hour (10.9 km/h) over the ground, was recorded in a famous photograph. The next two flights covered approximately 175 feet (53 m) and 200 feet (61 m), by Wilbur and Orville respectively. Their altitude was about 10 feet (3.0 m) above the ground. Here is Orville Wright's account of the final flight of the day:
Wilbur started the fourth and last flight at just about 12 o'clock. The first few hundred feet were up and down, as before, but by the time three hundred feet had been covered, the machine was under much better control. The course for the next four or five hundred feet had but little undulation. However, when out about eight hundred feet the machine began pitching again, and, in one of its darts downward, struck the ground. The distance over the ground was measured to be 852 feet; the time of the flight was 59 seconds. The frame supporting the front rudder was badly broken, but the main part of the machine remained undamaged. They estimated that the machine could be put in condition for flight again in about a day or two.
