Why did planes use different cooling systems in the ETO and PTO?

5/14/2013 • Ask Mr. History

Why were the majority of the planes used in the European Theater of Operations inline liquid cooled and the majority of planes used in the Pacific Theater air cooled radials? Was this done more out of designer’s preference, or was it more for necessity?



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Dear Jeremy,

I was not aware that there was so much of a difference in how many planes were liquid cooled and how many were air cooled in either theater. Certainly the U.S. Army Air Forces used its share of liquid cooled Curtiss P-40s, Lockheed P-38s and North American P-51 Mustangs throughout the Pacific and Asia, as did the British Commonwealth with its Hawker Hurricanes, Supermarine Spitfires, Bristol Beaufighters and deHavilland Mosquitoes. The two exceptions that may account for your impression are the U.S. Navy, which favored air-cooled radial engines in all its carrier planes, and the Japanese, who had trouble producing reliable liquid cooled engines—both of their best known liquid-cooled planes, the Kawasaki Ki.61 and Yokosuka D4Y, were later modified to use radial engines, and both performed better when they did.

If you extend the ETO into Africa and the Mediterranean, another factor was the sand and dust of the deserts, as well as Sicilian and Maltese airfields and in the Russian steppes in summer. For these environments, enclosed inline engines were easier to protect using tropical sand filters over the intakes, than were the more exposed radials.



Jon Guttman
Research Director
World History Group
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