Kitty Hawk in a Box

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ack in Dayton, Wilbur received an invitation from Octave Chanute to address the Western Society of Engineers. This was a great honor and a tacit recognition of the value of the Wright brother’s experiments. Wilbur was inclined to politely refuse, but Katharine hounded him into accepting.

Chanute’s kindness and Katharine’s persistence put Wilbur and Orville back on track. To prepare his speech, Wilbur had to carefully think through the results of his and Orville’s 1900 and 1901 experiments. Because their machines did not produce the expected lift, the brothers had begun to suspect that the data produced by Otto Lilienthal -- which every other scientist in the field took for granted were incorrect. The more they discussed it, the more convinced they became. Wilbur decided to stick his neck out and say so in his speech.

To his relief, the speech which Wilbur simply called "Some Aeronautical Experiments" was well received and a copy was published in the prestigious Journal of the Western Society of Engineers. But now that the brothers had declared the late, great Lilienthal wrong, what data should be used to replace his tables of lift and drag? The brothers decided they would have to produce their own tables. While at Kitty Hawk, George Spratt had suggested an apparatus that balanced lift against drag to measure both these quantities more accurately, and now they set about designing it. First they built a balance from a bicycle wheel mounted so it revolved horizontally. To its rim, they attached a flat plate and a curved plate 90 degrees apart. In a steady wind, the curved plate – a miniature wing could be set at an angle to the air stream so that the lift generated by air rushing over its surface would be balanced again the drag on the flat plate set perpendicular to the wind. If the lift and the drag were equal, the wheel would not revolve. Wilbur and Orville set the curved plate at the angle predicted by the Lilienthal tables, mounted the wheel to one of their bicycles, and pedaled like mad. As the air rushed over the plates, the wheel turned. Something was indeed amiss with either the data or the method that Lilienthal used to predict lift and drag.

Although ingenious, the bicycle apparatus was too crude (and too exhausting) to make accurate measurements. So the brothers built a wind tunnel from an old grinder and scraps of wood, and made delicate balances from hacksaw blades and bits of wire. They tested a variety of wing shapes in the tunnel and by mid-December 1901, they had made a surprising discovery. Lilienthal’s tables were, by and large, correct! But another number in the equation he used to calculate lift, the coefficient of air pressure, was way off the mark. This number had been developed in the mid-eighteenth century by an English engineer, John Smeaton, to design more efficient windmills. It had been in general use for nearly a century and a half, long enough to be accepted as gospel.

Wilbur and Orville also found that the shape of Lilienthal’s wings the camber - was inefficient. The curves of the German’s wing were sections of a circle. The highest point was in the center of the chord, midway between the leading and trailing edges. Wilbur and Orville found that a wing produced much more lift if its curve followed the shape of a parabola, with the high point about one quarter of the chord behind the leading edge.

This was the turning point. The wind tunnel experiments were the brother’s first venture into pure aeronautical science. It was tedious and time-consuming work, testing one miniature wing shape after another at 45 different angles to the air stream in the tunnel. It disproved their original assumption that the Lilienthal’s data tables were wrong but it pointed the way to the real problem and produced the knowledge that enabled the Wright brothers to build an aircraft with enough lift to support their weight in the air. This freed them to concentrate on the original problem they had set out to solve control.


Will and Orv conducted their initial air foil tests with a strange apparatus mounted to the front of a bicycle.

To make more precise tests, they built a wind tunnel.

The tunnel had a scoop with two sets of "straighteners" to provide a smooth air flow.

They also devised a lift balance...

...and a drag balance to test the characteristics of over 200 miniature air foils.

They recorded the results of the wind tunnel tests on scraps of wall paper.

Then they painstakingly compiled them in notebooks so they could compare the air foils

In Their Own Words
  • "Some Aeronautical Experiments" -- Read the complete text of Wilbur's speech to the Western Society of Engineers as it was published in their journal in December 1901. Note that there were some changes that Wilbur made to the published version, so we don't know exactly what was said in September. It's thought that Wilbur was somewhat more critical of Lilienthal's lift data in the speech, but mollified this after he was well into his wind tunnel research and had found that Lilienthal's data was correct.

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"Aviation is proof that – given the will – we can do the impossible."
 Eddie Rickenbacker



The Wright Story/Inventing the Airplane/Wind Tunnel Experiments

Part of a biography of the Wright Brothers
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