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Aviation History
1928
1928 - 0491.PDF
JUNE 14, 1928 THE CURTISS "CHIEFTAIN" ENGINE A 600-H.P. Air-Cooled Radial of Novel Design By ERIK HILDESHEIM IN the American National Advisory Committee for Aero-nautics Annual report for 1927 the first reference was made to a new " Hex " engine of the Curtiss Aeroplane and MotorCo., Inc. The name stood as an abbrevia- tion for " hexagonal," to indicate the newcylinder arrangement of this latest radial aero engine, which has now been finallynamed " Chieftain." The Curtiss company has, in thus enteringthe field of air-cooled engines, had the co-operation of the United States Army AirCorps during the two years of development. Flight tests were begun immediately afterthe Detroit Aero Show, at Mitchel Field, the Army aerodrome on Long Island adjoin-ing the Curtiss establishment at Garden City. The successful preliminary trials areto be continued by the Air Corps on Wright Field, Dayton, Ohio. The first " Chieftain "has been installed in a standard two-seater Curtiss " Falcon " observation and attackbiplane. The test flights were carried out by Lieut. H. P. Gaines, the Army pilotstationed at the Curtiss factory, and by the company's veteran test pilot " Casey " Jones. It is emphasised that for the first timehas the substitution of a radial air-cooled aero engine for a water-cooled edition notonly resulted in improved performance with regard to increased climb and ceiling, butthe usual simultaneous sacrifice of several miles per hour in top speed has at thesame time been overcome. The " Falcon " maintained the same speed as attainedpreviously with the Curtiss D.12 water- cooled V type engine, viz., 158 m.p.h. TheD.12 is, it will be remembered, of specially narrow construction. A comparison of thetwo power plant installations brings out the fact that the water-cooled engine type scoresin permitting a narrower fuselage beam, but has head resistance added by the radiatorunderneath. Developing 600 h.p., the Curtiss " Chieftain " is not onlythe highest-powered radial aero engine that has so far been produced in America, but the design differs from all previous THE NEW CURTISS " CHIEFTAIN " ENGINE :' Three-quarter front view. The unusual cylinder arrangement should be noted. THE NEW CURTISS "CHIEFTAIN" ENGINE: Three-quarter rear view. The engine is fitted with a supercharger. 447 practice in cylinder arrangement. Insteadof having one row of cylinders arranged radially, as in the Bristol, Wright and Pratt& Whitney types, or the offset two-row arrangement of the Armstrong-Siddeley" Jaguar " and adopted by Lorraine-Dietrich the " Chieftain " has two rows of cylinders,one behind the other with six cylinders arranged hexagonal! y in each row. Thisarrangement permits a common overhead camshaft drive for each two cylinders as inthe water-cooled in-line type of engine, and reduces the overall diameter of the engine,which means again less head resistance and increased high speed. The frontal area perhorse-power of the " Chieftain " is claimed to be about half that of the conventional9-cyhnder air-cooled radial. In fact, the overall dimensions of the 600-h.p. " Chief-tain " is, with 45 ins., the same as for the 220-h.p. Wright " Whirlwind." FLIGHT has been privileged by the makersto inspect, through a correspondent, the engine at Mitchel Field, K.Y., and to be firstin Europe to publish details about this interesting engine development.* It isstated that no difficulties have been ex- perienced so far in keeping the rear cylinderscooled. The confirmation of this in further extensive tests is of no little importance, asthere should then be no objection to increas- ing the number of cylinders in line to four. * Unfortunately pressure on our space has prevented publication until now, although the article has been ill hand for several weeks.—ED.
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