AIR-COOLED ENGINES.

New Zealand Herald, Volume LXVII, Issue 20722, 15 November 1930, Page 8 (Supplement)

AIR-COOLED ENGINES.

development in ten years. Ten years ago the water-cooled aeroengine was supreme in all fields; there was no airworthy air-cooled engine of moderate or high power in existence throughout the world, the original type, the rotary, having failed, through inherent limitations, to keep pace with the developments in power output, economy, and reliability brought about under the stimulus of the war.

Although at this time air cooling for aero-engines appeared obsolete, a great deal of research work upon the subject was progressing among those who felt that direct cooling was the logical method for use on an aero engine, and that it opened up possibilities for tho radial typo of engine, which appeared exceptionally attractive from the points of view of design and manufacture. The outcome was the appearance of a British nine-cylinder air-cooled, radial engine, developing 380 brake horse-power for a complete weight of 7501b. This engine in 1921 successfully completed the Air Ministry's type test, being the first air-cooled aero-engine of this type in tho world to pass an official test of this nature.

The completion of this official test was undoubtedly a landmark in the history of air-cooling, and a turning point in the fortune of the air-cooled aero-engine. It attracted the attention and stimulated the interest of those aircraft designers who realised the possibilities opened up. Since that date much progress has been made; at first slowly, then, as old prejudices were overcome and actual performance began to speak, the circle of users widened, until now the air-cooled engine is almost universally employed for private and commercial machines and for a big proportion of military machines also. To summarise the progress made in ten years, it may be pointed out that the weight per horse-power has been reducd by 25 per cent., the power output increased by 50 per cent., and the period between overhauls increased by 700 per cent., with a corresponding increase in the reliability of the engine and the life of the main components. We have now engines of 500 h.p. weighing 7501b., with fuel consumption of 0.51 b. per horse-power-hour, covering approximately 50,000 miles between overhauls, and costing approximately £3 per horse-power, which compares favourably with other sources of motive power.