Returning to Dayton after their 1901 glider experiments at Kitty Hawk, Orville and particularly Wilbur were dejected. The glider did glide but the lift generated by their glider was much less than they had expected and they experienced control problems as well. Wilbur was so puzzled that he declared, “Not within a thousand years would man ever fly.”
Shortly after returning home, an unexpected event shook Wilbur out of his funk. He received a letter from his friend, Octave Chanute inviting him to be the featured speaker at the upcoming meeting of the Western Society of Engineers in Chicago.
His immediate reaction was to refuse the invitation. Katharine, however, thought it would be a wonderful occasion to introduce her brother to influential people. She prevailed upon him to accept.
In a letter to their father Milton, she admitted, “Will was about to refuse but I nagged him into going.”
There was one other problem. Wilbur didn’t have any suitable clothes to wear for such an occasion. Orville, who always dressed well, offered his.
“We had a picnic getting Will off to Chicago,” Katharine wrote to her father. “Orville offered all his clothes so off went Ullam (Wilbur), arrayed in Orv’s shirt, collars, cuffs, cuff-links and overcoat. We discovered that to some extent clothes do make the man for you never saw Will look so swell.”
“We asked him (Wilbur) whether it (the speech) was to be witty or scientific,” wrote Katharine, “and he said it would be pathetic before he got through with it.”
Wilbur titled his speech, “Late Gliding Experiments.” Thinking about what he was going to say forced him to think seriously about what caused the lift problem. He decided that the trouble was with the Lilienthal data for curved airfoils that they had used to calculate wing size and shape.
In his Chicago speech, Wilbur boldly declared that the data in the Lilienthal tables contained serious errors. “The lifting capacity seemed scarcely 1/3 of the calculated amount.”
The speech was printed in the December, 1901 issue of the Journal of the Western Society of Engineers. The written version, however, was toned down somewhat. At this point Wilbur had no proof of his claim.
Wilbur also told his audience that “… if you are looking for perfect safety, you will do well to sit on a fence and watch the birds; but if you really wish to learn you must mount a machine and become acquainted with its tricks by actual trial.”
The speech was important because it gave Wilbur a new boost in confidence. These were people of high position. Their acceptance of what he said was a big moment for him.
The Wind Tunnel Experiments
The Wrights decided they needed to generate their own data to support their assertion that there was something wrong with the historical data they were using in their calculations. These test reveal the true genius of the Wrights.
Orville designed and their employee Charlie Taylor built a wind tunnel.
It consisted of a wooden box, six feet long, sixteen inches on a side, with a window on top that allowed the interior to be viewed. A fan mounted at one end was capable of producing 25 to 35 mph winds. They also created the instrumentation necessary to measure lift and drag forces at various angles and the effect of lift on varying wing curvatures as well as leading and trailing edge thickness. This was the first use of a wind tunnel to conduct aeronautical research.
Initially, they had mounted a bicycle wheel rim free to spin horizontally on a bike to test the wing shapes. The results showed they were on the right track, but the apparatus didn’t work very well.
Orville followed that up by building a small wind tunnel out of a starch box while Wilbur was in Chicago.
Their final wind tunnel was one of just ten existing in the world and the third in the U.S. The other wind tunnels were in academic environments and were used for specific airflow studies. The Wrights were interested in designing a wing, not theoretical studies.
The one trouble they had with the wind tunnel was that it produced too much turbulence. To correct the problem, they built a baffle in front of the fan. Modern wind tunnels place the fan at the other end so as to pull the air through the tunnel.
They conducted parametric studies (e.g. compare long, narrow wings with short, narrow ones) with nearly 200 different miniature metal wing foils in their wind tunnel, including stacked wings. Based on this data they determined the most efficient shape or configuration to create the most lift with the least drag. In the course of their tests over a period of only two months they redefined aeronautics for the next century.
Among other things, they proved the fallacy of sharp edges at the front of wings, the inefficiency of deeply cambered wings and the inefficiency of wings with low aspect ratio (short length, narrow wings). These were design features thought important by others.
They found that the Lilienthal data was valid only for the specific shape of the wing used by him. That and another factor they discovered was in error, known as the Smeaton coefficient, caused them to overestimate the lift of their gliders by 40%.
Wilbur wrote to Chanute: “I am absolutely certain that Lilienthal’s table is very seriously in error. But that the error is not so great as I had previously estimated.” (Wilbur found that the Lilienthal data wasn’t that much in error, the major error was in the value of the Smeaton coefficient.) Chanute, had trouble grasping their ideas.
Now, for the first time, wings could be designed efficient enough to support the flight of a machine. This was an important breakthrough because the Wrights established an important concept ignored by others. It is the wings, not the engine, which lifts an airplane into the air.
Their wind tunnel results permitted them to rapidly close in on being able to fly. Everybody else was designing “full scale.” Build a full-scale glider, see the results; then go back and build another one. This was a wasteful trial-and-error approach that cost money and time.
In contrast the Wrights completed all of their work in six weeks by working fourteen hours a day and finished in time to enjoy Christmas with their family.
The glider experiments at Kill Devil Hills in 1902 were to put to the test all the Wright Brothers research on flight. They knew they were closing in on the secret of flight.
Their data exceeded anything that was to be available for the next decade. They used their new data to build a larger glider that for the first time added a twin tail. Also, they changed the manipulation of the wing warping from foot control to the movement of the hips in a cradle on the lower wing.
Both the wing warping and the elevator controls were made more instinctive for the pilot. For example, the pilot would shift his weight to the high wing when the glider tipped.
Back in 1899 the brothers thought they might make some contribution to man’s effort to fly. Now they were confident that they could solve the problem of flight by themselves.
Orville later wrote, “When we were carrying on our wind-tunnel work we had no thought of ever trying to build a powered plane. We did the work just for the fun we got out of learning new truths.” After the plane’s performance affirmed the accuracy of their tables, Orville said, “we saw it would not be hard to design a man-carrying power aeroplane.”
The Third Trip to Kitty Hawk
The prior trips to Kitty Hawk were difficult and living was basic outdoor camping. This trip they were determined to camp in comfort.
The trip to Kitty Hawk, unlike the first two, was problem free. Upon arrival on August 28th they set about expanding and improving the crude building they had built the year before that was badly in need of repair. They now had a combination kitchen, dining room and bedroom. Their dining table consisted of oilcloth over two thicknesses of burlap. Their beds were reached by a ladder and consisted of two thicknesses of heavy burlap stretched between wooden frames up among the rafters. It was rustic, but a vast improvement from tent living.
“Will is thin and so is Orv,” Katharine wrote to their father. “They will be all right when they get down in the sand where salt breezes blow, etc. They think that life at Kitty Hawk cures all ills you know.”
Soon after arrival, they had an uninvited guest, a mouse, whose noises while searching for food kept them awake at night. Orville built a mousetrap to get the mouse. He confidently called it the death trap.
That night Orville was awakened with the mouse crawling over his face. Orville, with his dry humor, commented that the mouse was waking him up to put more corn bread in the trap.
He never did catch the smart little mouse. It was found dead ten days later under a trunk.
It took three weeks to assemble their glider.
During the day, the Wrights’ concentrated on flying. Wilbur in his Chicago speech said that the key to the secret of flying is practice. It was like learning to ride a horse.
One of their critical concerns was whether the wings they had designed using the data from their wind tunnel tests would generate sufficient lift. They based the design of the glider’s wings on airfoil number 12.
Their test data predicted a long, narrow wing is more efficient than a shorter one with the same area. The 1902 glider’s wing span was ten feet longer than the previous year’s glider and the cord was two feet shorter. As expected, they found the 32-foot wings with a 5-foot cord and chamber of close to 1:30 provided excellent lift.
Another feature of their new glider was that the wings were set in a negative dihedral. In other words they drooped. This feature provided greater stability and pilot control.
Perfecting the Turn
They had another concern. This one was with the wing warping mechanism that they used to control roll from side-to-side.
The design provided for the wings to be warped by the sideways movements of the pilot’s hips. The pilot was prone in a cradle (used for the first time) attached to warping wires that in turn were attached to the wings. In such a fashion the pilot could control the lateral direction of the glider.
They had added a fixed vertical double tail to their new glider to improve control while making a turn. They found that control was improved but not perfect.
Performance exceeded expectations except under some mystifying conditions, instead of the glider righting itself when the wing warping was applied, the craft would go into a tailspin. The Wrights called the phenomenon “well-digging,” because one wing tip would be forced into the ground with a screwing action.
This was a serious problem because most flying accidents are caused by a stall-spin sequence.
Orville solved the problem. One night he had trouble sleeping because he drank too much coffee. Not one to waste time, he thought about the problem. His solution was to change the double tail to a single tail and make the tail movable like a ship’s rudder.
As was typical, when one Wright brother had an idea, the other would improve on it. Part of their success in solving problems was derived from the fact that they were a great team.
Wilbur suggested that the wires used for wing warping should also be interconnected with the rudder control wires. In that way the two could be synchronized.
The glider could now be rolled left or right while still maintaining stability and control in flight. Also, the pilot could control two things at once, instead of three.
The wing warping cradle mechanism simultaneously controlled the wings and the tail, and a vertical lever operated by hand was used to control the elevator. In this way they could perform the basic aerial maneuvers necessary for controlled flight about three axes.
Some 1,000 glides, the longest being 622.5 feet in 26 seconds, demonstrated that they had solved most of the problems of stability and control and had the first workable airplane. They demonstrated that control and stability were related and that an airplane turned by rolling. The glider could hover like a bird, and turn and fly at right angles to the wind. Orville longest flight was 615.5 feet.
Their basic patent issued in 1906 was based on their concept of flight control used on this glider. The Wrights were forced to defend their patent many times, but never lost a court fight. It has withstood the test of time and still defines the basis for flight of all machines that fly, including the space shuttle.
Visitors in Camp
Octave Chanute asked the Wrights if he could bring two gliders of different designs to their camp for testing. Chanute wanted them to observe these designs with the hope that the gliders would attain automatic stability in flight. The Wrights humored Chanute, believing a better approach was to use human control as they were doing.
Chanute brought with him Augustus Herring to assemble and fly the gliders. One glider was a multi-wing machine that Chanute had designed, and the other was an oscillating-wing machine that a C. H. Lamson, of kite fame had designed. Neither flew successfully.
Herring turned out to be a scoundrel who would cause the Wrights trouble in the future. For example, after the Wrights filed for their patent in 1903, Herring wrote them and falsely claimed he held a prior patent on a machine similar to theirs and wanted a 1/3 interest in their machine.
Also in camp were George Spratt, a flying enthusiast and friend whom the Wrights invited, and a surprise visitor, their older brother Lorin.
Gliding with Ease
Orville and Wilbur made up for lost time after the “crowd” left.
“The past five days have been the most satisfactory for gliding that we have had,” Orville wrote Katharine. “In two days we made 250 glides, or more than we had made all together up to the time Lorin left. We have gained considerable proficiency in the handling of the machine now, so that we are able to take it out in any kind of weather. Day before yesterday we had a wind of 16 meters per second or about 30 mile per hour, and glided in it without any trouble. That was the highest wind a gliding machine was ever in, so that we now hold all the records! The largest machine we handled in any kind of weather, made the longest distance glide (American), the longest time in the air, the smallest angle of descent, and the highest wind!!! Well, I’ll leave the rest of the “blow” till we get home.”
Orville and Wilbur were having fun flying.
After five weeks of testing, they broke camp October 28th to return to Dayton.
They were ready to work on the design of a new machine that they proposed to propel through the air with propellers driven with a gas engine.
Note: A reproduction of the 1902 glider that was built under Orville Wright’s guidance is on display at the Wright Brothers National Memorial, Kitty Hawk, N.C.