History of aicraft piston engines

T he most successful diesel airplane engine was the

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Unformatted text preview: 510 lb. Although diesel engines had been used earlier in lighter-than-air craft, t his was t he f irst t o power an a irplane. (Photo A-2388) e ngine and its designer and manufacturer were the recipient of the Robert J . Collier trophy for 1 931; h owever, it never became an important airplane p owerplant. The Guiberson air-cooled radial diesel engine appeared about t hree years after the Packard, receiving a CAB Approved-Type Certificate 79, b ut was never widely used. T he most successful diesel airplane engine was the Junkers Jumo a 6-cylinder, opposed-piston, water-cooled engine (fig. 60), the development of which was started about 1920. This engine was used to a limited extent in German military airplanes and in German air transport, in the late 1930s. A model fitted with a turbo supercharger powered a high-altitude p hotographic reconnaissance airplane of World War II, the Junkers J u 86P, b ut by that time the engine was obsolescent. N ACA ( National Advisory Committee for A eronautics, later the N ational Aeronautics and Space Agency, NASA, Washington, D .C.) conducted exhaustive research directed toward the development of aircraft Diesel engines during the decade 1930-1940. This work was centered on injection-system development and combustion-chamber design. No multicylinder engines were built. For reference to this research see Index of NACA Technical Publications listed in the first section of the bibliography ( p. 9 6), and also that on diesel engines (p. 112). T he Napier Nomad engine, a 2-cycle diesel compound powerplant was designed after World War II for exceptionally high specific output, but it was made obsolete by the gas turbines before full development. N umerous other aircraft diesels were built and test flown, mostly in E urope, but by the beginning of World War II, and with the general use of high octane fuels, it became evident that the diesel engine could not c ompete with the conventional spark-ignition type, and its development t erminated. The research work of the NACA on diesel engines for aircraft d uring the late 1920s and early 1930s was extensive and outstanding, but it found no practical application. GASOLINE ENGINES. T he earliest 2-cycle aircraft engine flown successfully was built in England by the New Engine Company, Ltd. ( NEC), in 1909. I t was used in a B ritish-Wright a irplane of that period. T he cylinders were cross-scavenged with a R oots-type s cavenging pump. F rom 1909 to 1912 both air-cooled and water-cooled NEC engines were b uilt having 2 to 6 cylinders and 20 to 90 horsepower. A g reat many 2-cycle gasoline aircraft engines have been proposed, a nd many were built experimentally. Most of these were of the crankcasecompressor type, now common in outboard marine engines. The attraction of this type of engine lies in its mechanical simplicity and low cost, but it T WO-CYCLE 60 h as serious drawbacks for aircraft use, principal among which are its high fuel consumption when used with a carburetor, and its tendency toward misfiring and stalling at light loads. Most of the proposals have been for small, low-cost engines, but so far none has been de...
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