AIRCRAFT PROPULSION — TAYLOR 249 



of efflux cannot be exceeded without putting the flame out." The 

 early jet engines encountered this same problem. 



Of course, steam ceased to be of importance for aircraft after flights 

 by the Wright brothers and others had demonstrated the superior 

 qualities of the internal-combustion engine. Steam was given the 

 final coup-de-grace by a United States officer, brought up on steam 

 power, who reported in 1926, "On the basis of these three considera- 

 tions (weight, economy, air resistance) they (steam powerplants) are 

 absolutely impossible." My own opinion is not so extreme. If steam 

 power was without competitors, we would have successful steam air- 

 craft today, but at a considerable sacrifice in performance and per- 

 haps also in safety. 



Steam power continues to have an emotional appeal to many people, 

 and interest in steam power on the part of such enthusiasts continued 

 into the 1930's. A Travelair biplane powered with a steam engine 

 by Besler was actually flown in California in 1932. 



INTERNAL-COMBUSTION ENGINES 



The earliest successful aeronautical application of this type of 

 power appears to be in a dirigible balloon flight by Paul Haenlein in 

 Germany in 1872. A 4-cylinder 5 hp. (40 r.p.m.) Lenoir engine using 

 coal-gas fuel was used. The Lenoir engine was the first commercial 

 type of internal-combustion engine. The cylinders drew in air for 

 half the stroke and fired at atmospheric pressure at midstroke. Effi- 

 ciency was low — about 5 percent. 



The relatively light-weight and relatively efficient "Otto-cycle" 

 gasoline engine began with developments in England and Germany 

 in the 1880's, stimulated by automobile development. Its application 

 to aircraft came soon after. The first flight with this type engine 

 was apparently that of David Schwartz in Germany in a dirigible bal- 

 loon in 1897. 



Santos Dumont flew a dirigible in Paris in 1898, equipped with 

 a pair of "tricycle" engines in tandem, rated together at 3i/^ hp. and 

 weighing, it is said, 66 pounds, or 19 pounds per hp. These engines 

 were probably forerunners of the 3 hp. Clement engine used by Du- 

 mont for his one-man dirigible airship flown during the summer of 

 1903. This engine was a two-cylinder Vee type, air cooled, and 

 weighed 8.8 pounds per hp. 



The first successful heavier-than-air flight powered by a gasoline 

 engine was that of Langley's y^^-size model, which flew 350 feet on 

 June 18, 1901, and 1,000 feet on August 8, 1903. The engine (pi. 3, 

 fig. 2) was a 5-cylinder air-cooled radial, designed and built by 

 Stephen M. Balzer and redesigned and rebuilt by Charles M. Manly. 

 It gave 3.2 hp. at 3,000 r.p.m. with a weight of 7 pounds (see table 



