AIRCRAFT PROPULSION — TAYLOR 289 



"H" type engine used in British fighters toward the end of World 

 War II. The Eolls-Royce "Eagle" (not to be confused with the 12- 

 cylinder Eagle of World War I) was a 24-cylinder "H" type engine 

 with sleeve valves, very similar to the Napier "Sabre." It was de- 

 veloped after the war, too late to compete with the rapidly developing 

 jet and turbine engines. 



4. Diesel aircraft engines. Diesel engines built by Maybach were 

 used in Zeppelin and other rigid airships in the 1920's. The first 

 Diesel engine to power an airplane was a Packard air-cooled radial 

 (pi. 27, fig. 1) designed by L. M. Woolson, who was killed in a crash 

 (due entirely to bad weather) of an airplane powered with one of 

 these engines before the development was completed. The Packard 

 Diesel received CAA type certificate No. 43 on March 6, 1930. It set 

 the world's nonrefueling duration record for heavier-than-air craft on 

 May 25-28, 1931. This record still stands. This engine and its 

 designer and manufacturer were the recipient of the Robert J. Col- 

 lier trophy for 1931. However, it never became an important airplane 

 powerplant. The Guiberson air-cooled radial Diesel engine followed 

 the Packard and received C.A.A. type certificate No. 79, but was never 

 widely used. 



The most successful Diesel airplane engine was the Junkers " Jumo" 

 6-cylinder opposed-piston water-cooled engine (pi. 27, fig, 2), 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 1930's. This engine also powered a high-alti- 

 tude photographic reconnaissance airplane of World War II, but 

 was obsolescent by that time. 



The Napier "Nomad" engine, a two-cycle Diesel compound power- 

 plant was designed after World War II for exceptionally high 

 specific output. It was made obsolete by the gas turbines before full 

 development. 



Numerous other aircraft Diesels were built and test flown, mostly in 

 Europe, but by the beginning of World War II it was evident that 

 the Diesel engine could not compete with the conventional spark- 

 ignition type, and development was then terminated. The research 

 work of the N.A.C.A. on Diesel engines for aircraft during the late 

 1920's and early 1930's was outstanding. 



5. Two-cycle engines. The Junkers Diesel engine, previously 

 mentioned, has been the only two-cycle aircraft engine to get beyond 

 the experimental stage. A great many two-cycle gasoline aircraft 

 engines have been proposed, and many were built experimentally. 

 Most of these were of the crankcase-compressor type, now common 

 in outboard marine engines. The attraction of this type of engine 

 lies in its mechanical simplicity and low cost, but it has serious 



