Authors: Tom D. Crouch
Wilbur was thirty-two years old in the spring of 1899. He realized that now was the time. He needed a challenge, a measure of himself—a problem that matched his skills and abilities.
The recognition that flight was such a problem did not come in a blinding flash of insight, but grew slowly during the years 1896–99. By the time he wrote to the Smithsonian, however, he had already made his decision. He would conduct a series of aeronautical experiments, picking up where Lilienthal, Chanute, and Pilcher had left off, and adding his own “mite” to the accumulation of engineering knowledge on which the final solution would be based. Wilbur had absolutely no idea how close that final solution was, but he assumed it was so distant he would not be involved in attaining it.
He began with a thorough course of readings based on the Smithsonian materials and Rathbun’s suggestions. He obtained a copy of Chanute’s
Progress in Flying Machines
, located copies of the
Aeronautical Annual
for 1895, 1896, and 1897, and read through back issues of popular magazines in search of flying-machine articles.
His initial foray into the morass of conflicting opinion, speculation, and guesswork that passed for the literature of aeronautics was an education. “Contrary to our previous impression,” Wilbur observed,
we found that men of the very highest standing in the profession of science and invention had attempted to solve the problem…. But one by one, they had been compelled to confess themselves beaten, and had discontinued their efforts. In studying their failures we found many points of interest to us.
At that time there was no flying art in the proper sense of the word, but only a flying problem. Thousands of men had thought about flying machines and a few had even built machines which they called flying machines, but these were guilty of almost everything except flying. Thousands of pages had been written on the so-called science of flying, but for the most part the ideas set forth, like the designs for machines, were mere speculations and probably ninety per cent was false. Consequently those who tried to study the science of aerodynamics knew not what to believe and what not to believe. Things which seemed reasonable were often found to be untrue, and things which seemed unreasonable were sometimes true. Under this condition of affairs students were accustomed to pay little attention to things that they had not personally tested.
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Wilbur spent three months, from June to August 1899, sifting through the chaff of aeronautical history and theory to arrive at a far more accurate understanding of the state of the art than men like Langley and Chanute who had spent decades in the field and written books on the subject. How did he do it?
Wilbur was a man who established a goal with care, then never lost sight of it. He was the perfect engineer—isolating a basic problem, defining it in the most precise terms, and identifying the missing bits of information that would enable him to solve it. Other students of the subject lost themselves in a welter of confusing detail; they were lured into extraneous, if fascinating, blind alleys that led away from the basic problem. Not Wilbur. He had the capacity to recognize and the dogged determination required to cut straight to the heart of any matter.
Some experimenters—Langley, for example—had come to the field
with their own preconceptions and cared little for the lessons to be learned from previous theorists. Chanute, on the other hand, had attempted to gather all the available information on the subject as an end in itself.
Instead, Wilbur went to the books in search of answers to the most fundamental issues. What did one
have
to know to fly? What portions of the flying-machine problem were well in hand? What problems remained to be solved? He emerged from his reading with the answers to those questions. Incredible as it may seem, no other major experimenter had taken such a reasonable approach to the work of his predecessors.
Wilbur summarized his conclusions in a lecture to a group of Chicago engineers in the fall of 1901. “The difficulties which obstruct the pathway to success in flying machine construction are of three general classes,” he noted. Such a machine would require wings that would lift it into the air; a power plant to move it forward with sufficient speed so that the air flowing over the wings would generate that lift; and a means of controlling the machine in the air.
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It seemed obvious that the basic solutions to the first two problems had already been achieved. Lilienthal, Langley, Chanute, and others had actually constructed wings that would lift them into the air. More important, Wilbur knew how they had done it. During the course of his reading, he had found the simple equations and the precise engineering data that would enable him to design his own wings when the time came. As his work progressed, he would undoubtedly encounter unknown aerodynamic problems, but he was confident that the groundwork was in place.
The same was true of power plant research. Langley’s steam-powered Aerodromes of 1896 had made unquestioned free flights of impressive length powered by onboard engines. Obviously the little Langley steam engines could not be used to power a full-scale machine, but the success of 1896 had demonstrated that it was possible to build an engine and propeller combination that would propel a set of wings into the air.
Over the next few years automobile experimenters would be concentrating all their energies to develop lighter and more powerful internal combustion engines. When Wilbur needed a power plant, the technology would be there for the taking.
Not all his contemporaries agreed with that. Samuel Pierpont Langley would spend the greater part of his time and resources between
1898 and 1903 developing the perfect aeronautical engine. He believed that surplus power would be required to overcome unforeseen aerodynamic inefficiencies.
Wilbur would have none of that. Long before he built a powered machine, he would have calculated precisely how much horsepower would be required to fly it. He would provide just that much, plus a bit of a margin, and trust to his calculations. The key difference between the attitude of these two men can be seen in their approach to the power plant question. Time would prove Wilbur Wright correct, and Langley disastrously wrong.
Wilbur’s brilliant analysis of the flying-machine problem had led him to the area of balance and control. So far as he was concerned, in the summer of 1899 “the problem of equilibrium constituted the problem of flight itself.” This area he would make his own.
There were good reasons why the fundamentals of aerodynamic control remained a mystery. To conduct research on active control systems, one had first to be able to fly. Model wings could be tested in flight, or in the safety of the laboratory; the power of an engine and the thrust of a propeller could be measured on the ground. But to test a control system one needed a flying machine large enough to carry a human being who could operate those controls.
The complexity of the joint issues of aircraft stability and control, and the inability to break out traditional modes of thinking, also worked to retard serious advances. The airplane was the first vehicle that would require control in three axes of motion. These axes can best be understood as three imaginary lines around which a machine in the air is free to rotate: Pitch (a horizontal line running from wingtip to wingtip); roll (a horizontal line running through the center of the craft from nose to tail); and yaw (a vertical line running directly through the center of the craft).
It was relatively easy to visualize the need to control an aircraft in yaw and pitch, and to imagine how that might be accomplished. The lessons of surface transportation could be applied directly: it seemed obvious, for example, that a rudder placed on the tail of a flying machine would function in the same way that it did on a ship. Going one step further, a horizontal rudder, or elevator, should enable an aviator to turn the nose of his craft up or down to climb or descend. Elevators already served precisely that function on primitive submarines.
In fact, the control of pitch and yaw would prove much more difficult
in actual practice. As the Wrights were to discover, an aircraft rudder and a ship’s rudder function in different ways. And while the elevator worked roughly as predicted, determining its optimum size and placement would prove the most difficult of the many control issues that the Wright brothers faced, and the last to be resolved.
Roll control was uniquely difficult—the fact that it might be necessary or desirable to control this axis did not even occur to many experimenters. Everyone realized there would have to be a means of balancing the wingtips, but men and women accustomed to the engineering of surface transportation rarely considered that a pilot might actually want to induce a roll.
The conceptual problems and the impossibility of testing any control system without first learning to fly were serious enough. But lurking behind them was the notion that it might not be wise to trust the operator with full control of his machine. Things would happen so quickly in the air. There would be no opportunity to pull over to the side of the road to think a while. Could a human being remain alert and capable of reacting instantly to sudden potentially catastrophic changes in the attitude of the craft? Would it not be better to design an inherently stable aircraft, one that would fly a straight and steady course, automatically maintaining equilibrium in all three axes? The pilot would intervene only when a change in direction or altitude was required.
Between 1875 and 1900, the search for stability dominated the development of active control systems. Octave Chanute, for example, had sought inherent stability in pitch and roll by means of the confusing array of multiplane wings rocking back and forth on the Katydid, and the spring-mounted cruciform tail of the 1896 two-surface machine.
Samuel Langley had actually achieved automatic stability in his 1896 Aerodromes. As an experimenter working with flying models, he had little choice but to do so; any model airplane flying free of control from the ground must be inherently stable. It must resist any force acting to move it from straight and level flight, and have some capacity to restore its balance if upset by wind gusts, for there is no pilot on board to operate controls.
Such inherent stability was not as difficult to achieve as one might suppose. Alphonse Pénaud had demonstrated automatic stability as early as 1871 with a series of small models powered by twisted skeins of rubber. A simple four-bladed tail was an essential element of the
design. The two vertical vanes on the top and bottom of the tail provided yaw stability, tending to keep the model pointed into the wind. Pitch stability was achieved by mounting the tail at a slight negative angle to the horizontal. This forced the nose up, which, Pénaud reasoned, was considerably better than having it pointed down.
But Pénaud’s most interesting contribution was his means of achieving roll stability. He gave the wings a slight dihedral, angling the tips up from the center of the machine. When the airplane was flying in balance, the airflow over the right and left wings was equal. If the craft tipped to one side, however, the low wing would move into a position parallel to the airstream, thus increasing the lift on that side and raising the wing back into equilibrium.
Langley incorporated all of the Pénaud features into his steam-powered Aerodromes of 1896, and planned to follow the same pattern in the large manned machine he was constructing for the Army. The Great Aerodrome, as it was already known, would have no provision for roll control. The pilot would be able to move the tail up and down for takeoff and landing; he would also have some control over a large rudder centered beneath the craft. Under normal circumstances, however, he would keep his hands completely away from the controls. In point of fact, Langley was building the world’s largest model airplane.
Wilbur’s philosophy of control was diametrically opposed to Langley’s. He believed that the operator of any vehicle ought to have a means of controlling the motion of his craft in every available axis—an idea firmly rooted in his experience as a cyclist.
The bicycle differs from all other surface vehicles in that it is inherently unstable in both yaw and roll. The cyclist must steer with the handlebars while at the same time maintaining lateral balance through subtle shifts in body position that will keep the machine upright. It was just as James Means had suggested: “To learn to wheel one must learn to balance. To learn to fly one must learn to balance.”
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Wilbur’s intuitive grasp enabled him to move beyond Means’s simple notion of balance to a recognition of the positive virtue of absolute control. He realized that one could take advantage of the subtle links between control in roll and yaw to produce a more maneuverable, and therefore safer, aircraft. The operator of the Langley Aerodrome would have to negotiate wide flat turns with the rudder alone; the wingtips might dip slightly into the turn, but would automatically
balance themselves once again as a result of dihedral. How much better and safer, Wilbur thought, to have the ability to intentionally lean, or roll, into a much tighter and fully controlled turn—as with a bicycle.
This essential truth had escaped Wilbur’s predecessors in the field. His grasp of the control issue is a perfect illustration of his approach to technical problem solving. He had an extraordinary ability—perhaps genius is the word—to mix essential principles involved in a given mechanical situation, and to apply that understanding to the solution of problems which, on the surface, seemed quite unrelated.
It was an intuitive process, based on visual and tactile perceptions. What Wilbur could see and feel, he could understand. Consider, for example, the way he reduced the complex business of turning a bicycle to the left into a series of concrete, graphic images:
I have asked dozens of bicycle riders how they turn to the left. I have never found a single person who stated all the facts correctly when first asked. They almost invariably said that to turn to the left, they turned the handlebar to the left and as a result made a turn to the left. But on further questioning them, some would agree that they first turned the handlebar a little to the right, and then as the machine inclined to the left, they turned the handlebar to the left and as a result made the circle, inclining inwardly.
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