Republic XP-47J (Superbolt) High-Performance Single-Seat Fighter Aircraft Prototype
Just one of the two contracted XP-47J high-speed fighter prototypes were realized before the project came to an end.
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The classic Republic P-47 "Thunderbolt" fighter of World War 2-fame went through many revisions during its time aloft. Born from the company's work on the P-43 "Lancer", the P-47 entered service with the same "razorback" dorsal spine and large nose-mounted air-cooled radial engine. In time, the "Jug" was advanced to include a bubble-style canopy and higher-performance. Some became true thoroughbreds and excelled at interception duties while others performed exceptionally in the ground-attack role. As either a fighter or fighter-bomber, there were few designs of the war that could match the return-of-investment seen in the American P-47, its design attributed to Alexander Kartveli.
During all this, the U.S. Army was always on the lookout for more of everything and, in November of 1942, contacted Republic to engineer a lighter-weight, higher-performing version of its P-47 (entering official service that same month). This new aircraft would fit an uprated engine in the nose that featured additional cooling and water injection for maximum power at altitude. Weight would be saved wherever possible including armament and fuel. An Army contract issued on June 18th, 1943 covered two XP-47J prototypes.
Engineers returned with a revised form of their P-47 which was designated "XP-47J". The design's engine cowling was refined with a smaller frontal area and this tight cover housed the Pratt & Whitney R-2800-57(C) engine within. The engine outputted at 2,800 horsepower and would drive a standard four-bladed propeller unit. Both the engine and propeller unit were off-the-shelf, in-service products which would aid in mass production of the aircraft. For weight savings, the wing mainplanes were revised to a lighter-constructed form and one of the four machine guns in each wing were deleted (as were some of the internal fuel stores which, in turn, reduced operational ranges). Additionally, some cockpit equipment was removed and the dorsal area aft of the cockpit was cut down. A true bubble-style canopy was not in play as of yet - instead a revised version of the basic P-47 framed canopy was added and this did help in improving vision out-of-the-cockpit for the pilot.