The Origins of the First Powered, Man-carrying Airplane The Wright brothers' "Flyer" of 1903 was not just a lucky effort by two bicycle mechanics from Dayton but the outcome of an intensive program of research, engineering and testing by F. E. C. Culick n a series of flights on December 17, they would have to follow a systematic vated the efforts, and so it was natural 1903, Wilbur and Orville Wright program of research and engineering. that the earliest ideas always entailed I became the first to pilot a powered He summarized his view in a lecture he the use of flapping wings. Sir George airplane. As is well known, they had de­ gave in September, 1901, at a meeting of Cayley (in 1799) was the first to under­ signed and built the craft themselves. To the Western Society of Engineers: "The stand that manned flight would be more this day, however, the notion persists problems of land and water travel were easily achieved if the means of generat­ that the Wright brothers were essen­ solved in the 19th century because it was ing lift were separated from the means tially bicycle mechanics who more or possible to begin with small achieve­ of propulsion. less stumbled on their successful design. ments and gradually work up to our Cayley is recognized as the originator Even among aeronautical engineers ig­ present success. The flying problem was of the airplane. His designs and conclu­ norance of what the Wrights accom­ left over to the 20th century, because in sions were based on careful observa­ plished is widespread. In tracing the this case the art must be highly devel­ tions and experiments. He conceived the steps by which the brothers arrived at oped before any flight of any consider­ configuration now viewed as being con­ their success, and in building a model of able duration at all can be obtained." ventional: a body or fuselage supporting their 1903 "Flyer" for tests in a wind Four years later the Wrights would have one main wing, with horizontal and ver­ tunnel, I have come to recognize how a practical airplane. tical tails positioned aft. He sucessfully remarkable their achievements in re­ Their invention of the powered, man­ flew gliders, one of them large enough to search, engineering and testing were. carrying airplane happened partly as carry a boy on at least one occasion. Their work deserves to be set in a richer a natural development from the work Cayley himself never flew. Among his historical context. of others. To an extraordinary de­ many other notable contributions were On the day of the first flights the gree, however, the Wrights' own contri­ demonstrations that curved surfaces are brothers took turns as pilot. Wilbur was butions were crucial. Their technical better than flat ones for providing lift; the pilot on the fourth, last and longest achievements were stunning, particular­ the idea that lateral balance or stability flight of the day, staying aloft for 59 ly when one considers where the effort can be gained by giving the wing a dihe­ seconds. Nearly four years passed be­ to achieve human flight stood in 1899. dral angle, that is, making it with raised fore anyone else was able to fly for as tips, and the concept of employing a long as a minute, and even then the ma­ Four Pioneers horizontal tail to achieve longitudinal chine was not fully controllable. By that stability. time the Wrights had developed a ma­ The people trying to build flying ma­ What Cayley began to comprehend neuverable airplane capable of flying chines had followed several strategies. were the intimate connections between for more than an hour. Observations of the flight of birds moti- the geometry of an aircraft, the forces As late as 1908, when the Wrights first flew publicly, no one else yet understood the need for lateral control, much less the function of the vertical tail. There­ fore no one else could execute proper turns. No one else knew how to make propellers correctly. Above all, no one else had pursued a comparable pro­ gram: doing the necessary research, con­ structing his own aircraft and doing his own flying, so that he understood the entire problem. The Wrights were able to outstrip all the other people who were trying to fly because they recognized the problems that had to be faced and solved. The brothers began their work in 1899, when Wilbur was 32 and Orville WRIGHTS' FLYER OF 1903, portrayed at the left in a view from the left side and at the right was 28. Wilbur, who was the informal in views from above and in front, was the first powered, man-carrying airplane to fly success­ leader in much of the work, realized fully. Its most distinctive feature was the forward horizontal control surface. The twin vertical 86 © 1979 SCIENTIFIC AMERICAN, INC acting on it and its stability in flight. An is provided mainly by the smaller hori­ longitudinal stability. Moreover, he un­ airplane has a vertical plane of symme­ zontal surface, which is usually placed derstood how the tail worked and gave try passing through its longitudinal axis. at the rear as Cayley advocated. Lateral the first explanation of its function in Motions that do not deflect the craft in stability is the effect of many causes, in­ prod ucing stable flight. directions out of that plane are called cluding the dihedral angle of the wings Otto Lilienthal, a mechanical engi­ longitudinal motions. The commonest and the vertical tail. The designs of early neer working in Germany, made major motion is pitching, in which the nose flying machines often included a verti­ contributions that directly influenced moves up or down. Sideslip, roll about cal tail for steering, by analogy with the the Wrights. In 1889 he published a the longitudinal axis and yaw about the rudder of a ship. The true function of book, The Flight of Birds as the Basis for vertical axis are collectively called later­ the vertical tail as a contribution to sta­ the Art of Aviation. that contained the al motions. bility was not apparent until the work of results of extensive experiments he had The tendency of any object in steady the Wrights. carried out with the help of his brother. motion to return to its initial state fol­ The giant of early French aeronautics That work provided the first useful data lowing a disturbance is called stability. was Alphonse penaud. He was the first on the lift and drag of curved airfoils. There are two kinds of stability, longitu­ to use wound strip rubber to power a Lilienthal also experimented in gliding, dinal and lateral, corresponding to the propeller-driven model airplane. Inde­ beginning in 1891, and became the first · two classes of motions of an airplane. In pendently of Cayley he conceived of the successful hang-glider pilot. He tried a modern aircraft longitudinal stability horizontal tail as a means of achieving both monoplane and multiplane gliders tail could not be moved except when the pilot warped the wings to the Wrights, fulfilled the function now uniformly done with ailerons. make a turn. Flying prone, he achieved warping by means of wires Wilbur and Orville Wright built the entire airplane, including the gas­ attached to a hip cradle. Wing warping, which was an invention of oline engine and propellers, which they had to design from scratch. 87 © 1979 SCIENTIFIC AMERICAN, INC and was killed while testing a mono­ ity. Although they were able to design enthal's death in 1896 aroused their in­ plane. their gliders to generate sufficient lift, terest in the problem of flying. In May, In the U.S. the most serious student of they had great difficulty maintaining 1899, Wilbur wrote to the secretary of aeronautics during this period was Oc­ balance in flight. They understood that the Smithsonian Institution asking for a tave Chanute, an eminent civil engineer. achieving balance meant making the list of the available literature on flight. With his writings and his own experi­ center of lift coincide with the center of Among the items he decided to buy was ments he brought Lilienthal's work to gravity. The difficulty arises because the Chanute's book Progress in Flying Ma­ the U.S. Because of his age (he was 68 in center of lift moves if the attitude of the chines, written in 1894. After stud ying 1900) he did no flying himself. He had aircraft is disturbed, as by a gust. In a the book Wilbur wrote to Chanute, initi­ several proteges who tested his gliders hang glider the pilot can restore balance ating an exchange of letters that contin­ and their own designs. by shifting his position in order to move ued for nearly 10 years. For most of that Chanute designed a biplane glider his center of gravity and change the atti­ period Chanute was a source of both that represents the beginnings of mod­ tude of the aircraft. If this maneuver is information and encouragement to the ern aircraft. (The design has served re­ accomplished correctly and consistent­ Wrights. The letters and the diaries of cently as the basis for several hang glid­ ly, the combination of the glider and the the Wrights constitute a detailed chroni­ ers.) Chanute adopted Penaud's aft tail pilot forms a stable system. cle from which one can reconstruct the for longitudinal stability, and for better When an aft horizontal tail is properly events leading to powered flight. lift he designed a cambered wing section installed, it will (as Penaud understood) similar to one tested by Lilienthal.