AIRCRAFT PROPULSION — TAYLOR 287 



Meanwhile, float-type carburetors were being developed for auto- 

 mobile use, and these were used by most aircraft engines after the 

 Gnome and Antoinette. The Wright brothers used float carburetors 

 on their later engines. 



Float-type carburetors were generally used for aircraft engines up 

 to about 1935. A floatless carburetor was introduced by Chandler- 

 Groves in 1935, and the Stromberg floatless injection-type carburetor 

 became operational about 1938. Since that time most military and 

 transport engines have used floatless-type carburetors, many of the in- 

 jection type. Light-plane engines have, generally, continued to use 

 float-type carburetors, although injection systems are available for this 



type. 



Direct fuel injection. — Injection into the individual cylinders was 

 used in gasoline engines for a short time on some Pratt and Whitney 

 Wasps in 1931-32. This method was developed to service use in 

 World War II in German military engmes. It was adopted by 

 Wright Aero Corporation for their R-3350 engine in 1944. 



Inlet-port injection. — Injection through nozzles located at each inlet 

 port has been used to a limited extent in light-aircraft engines since 

 about 1946. 



Stress 77ieasurement. — A very important contribution to improve- 

 ment in the structural design of aircraft engines was made possible by 

 the development of experimental stress analysis, which has been used 

 by the major aircraft-engine manufacturers since about 1940. An im- 

 portant contribution to this art was the development of "Stresscoat" 

 by E. S. Taylor and Greer Ellis in 1938. This method of showing 

 stress patterns by means of a brittle lacquer coating had been used by 

 the Germans earlier but was not known in this country until the work 

 of the above-mentioned persons. 



Miscellaneous. — Interesting historical developments have occurred 

 in bearing materials, fuel systems, exhaust systems, control systems, 

 fire extinguisher systems, and other elements, but space limitations 

 prevent their consideration here. 



UNCONVENTIONAL ENGINES 



Hundreds of unconventional types of aircraft engine have been 

 proposed, built, and tested. Among these may be mentioned: 



1. Numerous "barrel" or "revolver" type engines. In this type the 

 cylinders are positioned around the crankshaft with their axes par- 

 allel to it. Perhaps the best-known attempt was the "Almen" engine 

 of 1921. None ever flew, as far as I know. 



2. The Fairchild "Caminez" engine (fig. 19) was a4-cylinder radial 

 with rollers in the pistons operating on a two-lobe cam. This engine 

 received U.S. Department of Commerce No. 1 type certificate (June 



