The Navy and Liquid-Cooled Engines

Based on reading most accounts of the Naval aviation history, one would think that the U.S. Navy had no interest in liquid-cooled reciprocating engines for carrier-based airplanes after 1929. Certainly it only deployed ones powered by air-cooled engines thereafter. In fact, the Navy maintained an active role in liquid-cooled engine development into the early 1940s. One example was their selection for evaluation of a derivative of the Bell P-39 Airacobra, the XFL-1, in 1938. The Wright H-2120 was another such effort. It was a very unusual configuration - a twin-row radial engine, but with the six cylinders in the aft row lined up with those in the front row and each such pairing liquid-cooled. The objective was to minimize the frontal area of a radial engine and avoid potential problems with air cooling the aft row of cylinders. The Navy funded development of the H-2120 from about 1933 to 1936, when a 100-hour development test was run at 1,000 shp. At that point, both Wright and the Navy lost interest in pursuing this particular configuration, with the feasibility of air-cooling the second row of cylinders having been demonstrated.