Curtiss XP-37 (Allison Hawk) Fighter Prototype
The Curtiss XP-37 was an attempt by the USAAC to transform the radial-powered P-36 Hawk into an inline piston-engined fighter.
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The American Curtiss P-36 "Hawk" marked one of the earliest of the all-modern fighters to appear in the years leading up to World War 2 (1939-1945). It was joined by the likes of the British Hawker Hurricane and the German Messerschmitt Bf 109 but failed to find the same wartime success as its contemporaries. Completed with a Pratt & Whitney "Twin Wasp" air-cooled radial piston engine, 215 examples were built as the P.36 and a further 900 were exported under the "Hawk 75" designation. The design was eventually developed into the classic P-40 "Warhawk".
The United States Army Air Corps (USAAC) sought additional value in their P-36 to the point that they commissioned Curtiss in 1937 to develop the aircraft with the Allison V-1710 turbo-supercharged inline piston engine of 1,150 horsepower. This begat the prototype "XP-37" monoplane fighter which retained much of the original's components including its well-streamlined airframe. To compensate for the length and weight of the new engine installation at the nose (and to better balance the revised center-of-gravity), the cockpit was positioned further aft along the dorsal spine which immediately differentiated it from the earlier P-36.
In this configuration, the aircraft was flown for the first time during April 1937 and managed a maximum speed of 340 miles per hour against the P-36A's 313 mph top speed. However, the all-important turbo-supercharger proved troublesome during testing and there grew concern about the nose length and position of the wing mainplanes which considerably inhibited the pilot's forward vision. Views to the rear of the aircraft were no better as the raised fuselage spine and tail planes further masked any approaching danger from the rear.
Nevertheless, USAAC authorities were sold on the potential performance gains of this sleek entry and ordered the XP-37 in a service test form as the "YP-37" through a thirteen-strong batch order. Engineers continued to work on the turbo-supercharger but reliability remained an issue. A developmental-minded YP-37 managed a first flight during June of 1939 but the temperamental aircraft was soon passed over for a more promising - and conventional - venture, this to become the P-40 Warhawk which became an ultra-critical American fighter of the early-war years.