Curtiss XP-42, 23 February 1942. Curtiss XP-42. Testbed for streamlining cowlings around air-cooled engines. The Curtiss XP-42 was an experimental fighter built by Curtiss Aircraft in the late 1930s to research engine cooling and improving the performance of the Curtiss P-36. The fourth production P-36A (serial 38-004) became a development platform for a direct successor, designated XP-42 by the USAAC. The most striking difference with the P-36 was a longer, streamlined nose cowling (concealing a longer propeller shaft). These features attempted to improve the aerodynamics of the air-cooled radial engine. Because of this feature, the XP-42 superficially resembled aircraft equipped with in-line liquid-cooled engines (such as the P-40, another development of the P-36). When the XP-42 first flew in March 1939, it proved to be faster than the P-36. However, the P-40 was faster and the new nose cowling caused engine cooling problems that proved to be unresolvable, despite at least 12 sets o...