Like many of the American war-winning fighter aircraft of World War 2 (1939-1945), the Republic P-47 "Thunderbolt" was the subject of many experiments, modifications, and offshoots to help extract additional power and performance from the excellent airframe. The P-47D model became the definitive wartime production model and the promising, yet-developmentally troubled, P-47M was limited to just 130 examples before the company moved on the follow-up P-47N - which was given extended fuel stores to better cope with long ranges of the Pacific Theater. More radical conversions were still had between these more notable forms and the XP-47H was a late-war attempt to turn the "Jug" into an inline-engined fast fighter.
The XP-47H was born from two P-47D-15-RA production airframes ("Razorback" models) set aside specifically to test the new Chrysler XI-2220-11 16-cylinder inverted-Vee liquid-cooled inline engine promising up to 2,500 horsepower. These aircraft were pulled from Republic's production line in Evansville, Indiana, a facility set up to help offset the heavy industrial need for Thunderbolts in the American war effort. The H-model more or less retained the form and function of the P-47D but the new, and utterly complex, Chrysler engine installation meant that the rather basic fuselage of the P-47D would need to undergo considerable modification to accept the powerplant.
As a test bed, the fighter was stripped of all of its armament and "military" equipment. Unlike the "open-nosed" air-cooled radial piston engine fitted to the original D-models, the XP-47H was given an all-new forward section shaped around the liquid-cooled inline engine. The nose was very pointed thanks to the spinner which was streamlined with the general shape of the aircraft. The engine drove a four-bladed propeller unit and also caused the nose section to extend noticeably forward of the cockpit - limiting the pilot's forward vision. Under the nose was seated a cooling radiator air scoop designed to draw air as the aircraft reached speed and this gave the revised Thunderbolt a deeper side profile than normal and made a large aircraft appear even larger.
All other physical qualities of the D-model were retained including the elliptical wing mainplanes, single-finned tail unit, and tail-dragger undercarriage (retractable). The pilot sat at midships underneath a heavily-framed canopy which slid back on side rails. The raised fuselage spine of the Razorback Thunderbolts limited views to the critical rear of the aircraft - later remedied by the introduction of a bubble-style canopy design during the war.
The Chrysler inline proved more trouble than it was ultimately worth and delays incurred on that project naturally delayed the XP-47H program. As such, the H-model's prototype did not go airborne until July of 1945 and even then the intended axial flow supercharger tied to the engine was not in a ready state so a General Electric CH-5 turbosupercharger unit was substituted in its place.
With the program slowly progressing, engineers were optimistic for a maximum speed of around 490 miles per hour - making the H-model one of the fastest piston-engined fighters of the war. However, testing soon revealed that the XP-47H was a dead-end project - doomed by its troublesome engine, spotty development successes, and the end of the war in the Pacific come August 1945. During testing, the H-model recorded a maximum speed of 414 miles per hour, far short of the expected performance gains - and this without weaponry or military equipment fitted.
The project was eventually dropped by Republic despite the high investment already put into the fighter.
(OPERATORS list includes past, present, and future operators when applicable)
✓Air-to-Air Combat, Fighter
General ability to actively engage other aircraft of similar form and function, typically through guns, missiles, and/or aerial rockets.
Ability to intercept inbound aerial threats by way of high-performance, typically speed and rate-of-climb.
✓X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.
36.1 ft (11.00 m)
40.8 ft (12.45 m)
14.6 ft (4.45 m)
10,031 lb (4,550 kg)
17,637 lb (8,000 kg)
+7,606 lb (+3,450 kg)
(Showcased structural values pertain to the base Republic XP-47H Thunderbolt production variant)
1 x Chrysler XI-2220-11 liquid-cooled inline supercharged piston engine developing 2,500 horsepower driving a four-bladed propeller unit at the nose.
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