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The Heritage of Kitty Hawk [[line]] Part VIII - By Walter T. Bonney Copyright, 1956, by Fairchild Engine and Airplane Corporation The 14th annual report of the Aeronautical Society of Great Britain for the year 1879, contained the harsh, though true, judgment that: "Mathematics up to the present day have been quite useless to us in regard to flying." How different the situation has been in the past 50 years, when the science of fluid mechanics has been employed so fruitfully by mathematicians and physicists to unlock secrets of nature that could be used in explaining not only why it was possible for man to fly, but also how he could fly more successfully. To be sure, for centuries prior to the first flights by Wilbur and Orville Wright in 1903, men of mathematics had built, piece by patient piece, a body of knowledge that one day wold be of great value in the establishment of a new science - aerodynamics. There was Leonardo da Vinci, who in the 15th Century wrote that "the movement of the air against a fixed thing is as great as the movement of the movable thing against the air which is at rest." There was Sir Isaac newton, who, two hundred years later, published the monumental "Philosophia Naturalis Principia Mathematica" in which he stated the first theory of air resistance as deduced from the principles of mechanics and, perhaps equally important, pointed out that the same law applied equally to water and air. There were many others ... d'Alembert, Helmholtz, Bernouilli, Euler, Kirchhoff, Rayleigh ... Not all of the early statements of the principles of fluid mechanics were correct. In fact, the falseness of Newton's statement of proportionality between the force acting on a surface element and the square of the sine of its angle of inclination has been blamed by some critics for having been a delaying influence on the development of mechanical flight. More likely, the influence of Newton and other mathematicians on the efforts of the early aeronautical pioneers was negligible; they seldom had faith in theories. Beginning in the 18th century, the principles of fluid mechanics were rigorously appraised by engineers and physicists. Bodies in motion were studied, both in the air and in water, by use of a "whirling-arm" device (in the United States, for example, by Langley in 1886). A little later, the resistance of bodies moving through water was determined in towing tanks. The findings from such research tools were of interest to shipbuilders and munitions makers who had pressing need for means to improve the products of their yards and ordnance works. Newton in the 17th century had studied spheres which he dropped from the dome of St. Paul's Cathedral in London. Two hundred years later, Gustave Eiffel made similar experiments in Paris, from a platform high up on the tower which bore his name. In England, beginning in the 1870's, Herbert Wenham and Horatio Phillips devised successful wind tunnels, the most useful of the tools employed in aerodynamic research. As early as 1891, Nikolai E. Joukowski built a wind tunnel with a 2-foot-diameter test section at the University of Moscow. By the beginning of the 20th century, wind tunnels were being used also in the United States by the Wright brothers and Albert F. Zahm, and in France and in Germany. Such as the state of affairs in 1903 when the Wright brothers took to the air. Disillusioned by the inaccuracies they found in data such as Lilienthal had compiled from his glider experiments in Germany (Prelude to Kitty Hawk, Part III), they relied almost entirely upon the results of their own wind tunnel investigations. These they verified as best they could by measurement during flights of their gliders. Wilbur and Orville Wright continued, after 1903, to be self-sufficient. They had been the first to attain sustained flight in a machine heavier than air, and now, they concentrated upon two tasks: (1) The merchandising of their invention, and (2) the defense of what they believed to have been a development solely theirs. The latter effort, intensified by Orville after Wilbur died in 1912, may well have slowed the progress of aeronautics in the United States. Especially with respect to alleged infringement by Glenn Curtiss against the Wright patents, the litigation was long and often acrimonious. Elsewhere, the Wright patents had little retarding effect upon the vigorous forward push of aeronautics which began about 1906. Meanwhile, in Europe, the mathematicians were making real progress in developing theories that would explain, for example, the lift obtained by means of a curved wing at zero angle of attack. Frederick W. Lanchester, British engineer and automobile manufacturer, began his experiments and studies in 1894. In 1897, he read a paper to the London Physical Society which disclosed a remarkably sophisticated understanding of the physical concepts of modern wing theory. In 1907 and 1908, he published two volumes of his well-developed ideas. The importance of Lanchester's work was first recognized by the Germans, not the English. A logical explanation was given, in 1927, by Ludwig Prandtl: "...As a matter of fact we in Germany were better able to understand Lanchester's book when it appeared than you in England. English scientific men, indeed, have been reproached for the fact they paid no attention to the Page 11
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