Industrial Research 



139 



cent, but when applied to the tliree-engiiicd airplanes of 

 that day resulted in no increase in speed. This let! to a 

 fundamental investigation by the N. A. C. A. to de- 

 termine the cause and to find the remedy. By a 

 comprehensive survey of the net efficiencies of various 

 engine nacelle locations, the optimum position in the 

 wing was found. This N. A. C. A. (<ugine location 

 principle, together with other refinements, had a 

 revolutionary effect on military and commercial avi- 

 ation the world over. It changed military aviation 

 tactics, made long-range bombei-s possible, and forced 

 the development of higher speed pursuit planes. In 

 the commercial field it permitted the speeding up of 

 cruising schedules on tlie air lines from 120 miles per 

 hour of the Fords to the 180 miles per hour of the new 

 Douglas planes. The overnight transcontinental run 

 became possible and the air Hues vastly increased their 

 appeal to the public. Even in the midst of the depres- 

 sion, air line traffic boomed. 



The fourth great change in air-transport e<iuipment 

 came about without benefit of Government research. 

 It has its beginning during the First World War when 

 the General Motors Research Corporation and the 

 Cooperative Fuel Research Committee (Society of 

 Automotive Engineers and the American Petroleum 

 Institute) undertook research on the knocking of auto- 

 mobile engines. Tliis research evolved a method of 

 measuring knock qualities of a fuel by "octane num- 

 ber." Thomas Midgely found substances that would 

 raise the octane rating of gasoline and, in particular, 

 tetraethyl lead. The use of high octane fuel permitted 

 higher compression in engines, leading in turn to greater 

 power for the same cylinder volume and better fuel 

 economy. The air-transport industry did not benefit 

 from the results of this most important research until 

 1933 when leaded fuel was commercially available as 

 well as engines designed to use it. Since then the oil 

 industry has continued to raise the octane rating of 

 aviation gasoline and engine designers have correspond- 

 ingly increased the specific output of their engines. 



The technical improvement in both fuel and engines 

 has come from research by the industry, but high- 

 output engines and high-octane gasoline did not appear 

 on the airlines until the Army and Navy had established 

 the practicability of the combination and, by volume 

 orders, had made commercially available what was at 

 first only experimental. 



The fifth major improvement in the airplane also 

 came from the industry. The idea of a controllable 

 pitch propeller is to have a low pitch for take-off which 

 can be changed to a high pitch when high speed is 

 desired. The idea is not new, but the mechanical 

 difficulties are formidable. The desire for such a 

 solution did not become pressing imtil 1932 when it 

 was clear that pay loads could not be raised to an 



economical hn'cl without better take-off power. When 

 the controllable-pitch proi)eller was really needed, it 

 was found that a firm in tlu^ industry, which had been 

 conducting research lor many years, had a practical 

 type ready for ap[)lication. Since 1933 Hamilton- 

 Standard controllable-pitch propellers, following F. W. 

 Caldwell's designs, have been standard equipment on 

 all ITnited States airlines. The improved performance 

 due to landing flaps, N. A. C. A. cowls, high-octane 

 fuel, high-output engines, and controllable-pitch pro- 

 pellers all came at about the same time. Between 

 1935 and 1938, schedules were speeded up, frequency 

 was increased, and fares were lowered, and in 1939 

 airlines began to nuike money. 



Many other improvements beside these five major 

 ones have become possible, directly, as a result of 

 research, and indirectly, as a result of manufacturing 

 profits diverted to support research. A complete 

 survey and appraisal of research results and their 

 sources would be too long to record, but the nature 

 of a number of significant improvements is indicated 

 in the last part of this article. 



While improvement in the airplane itself is the funda- 

 mental cause of the growth of the manufacturing 

 business, air transport lines and the military and naval 

 air forces, it must not be forgotten that other factors 

 are essential. In air transport, for example, the 

 carriage last year of more than 2,000,000 passengers in 

 safety and comfort required careful planning and 

 sound policies Ity both the regulatory authority and 

 by management. Also, we have had new facilities 

 on airways and airports, with marked progress in 

 applied meteorology and in radio communications. 

 The radio equipment in one airliner today costs more 

 than did an entire airplane a few years ago. One 

 airline maintains a chain of radio stations of greater 

 number than any commercial broadcasting network. 

 Progress in aeronautics depends on progress in many 

 arts and sciences and on an alert management working 

 within a framework of wise regulation. 



Research Results Leading 

 to Improvements 



General Aerodynamics 



In 1901 the Wright Brothers budt a small wind 

 tunnel with which they determined, by systematic 

 experiment, the aerodynamic effects of wing curvature, 

 plan form, aspect ratio, and gap-chord ratio. These 

 studies are significant m view of later research which 

 has found only one other basic variable of wing design, 

 namely thickness. The Wrights also checked by means 

 of a glider the scale effect involved in converting model 

 data to apply to full-scale wings. From their research 

 data, the first successful airplane was designed and 

 built. During the next 10 years others took up wind- 



