Republic XP-47J Thunderbolt http://www.wpafb.af.mil/museum/research/p47-16.jpg http://www.wpafb.af.mil/museum/research/p47-17.jpg
From
http://home.att.net/~jbaugher1/p47_9.html :
The fastest version of the Thunderbolt was the XP-47J, which was proposed in November 1942 as a lighter-weight version of the Thunderbolt designed to explore the outer limits of the design's basic performance envelope. The XP-47J was fitted with a 2800 hp Pratt and Whitney R-2800-57(C) housed inside a close-fitting cowling and cooled by a fan. The ventral intake for the CH-5 turbosupercharger was separated from the engine cowling and moved aft. The four-bladed propeller was fitted with a large conical-shaped spinner. The wing structure was lightened and the armament was reduced from eight to six 0.50-inch machine guns. The contract was approved on June 18, 1943.
The XP-47J was a completely new airframe and not a conversion of an existing P-47D. The serial number was 43-46952. The XP-47J flew for the first time on November 26, 1943. On August 4, 1944, it attained a speed of 504 mph in level fight, becoming the first propeller-driven fighter to exceed 500 mph. At one time, it was proposed that the J model would be introduced onto the production line, but the advent of the even more advanced XP-72 resulted in plans for the production of the P-47J being abandoned before any more could be completed.
A proposal to adapt the XP-47J to use contrarotating propellers with an R-2800-61 engine was dropped.
Maximum speed of the XP-47J was 507 mph at 34,300 feet, range was 765 miles at 400 mph, 1070 miles at economical cruising speed. An altitude of 15,000 feet could be reached in 4.5 minutes. Service ceiling was 45,000 feet. Weights were 9663 pounds empty, 12,400 pounds normal loaded, 16,780 pounds maximum. Wingspan was 40 feet 11 inches, length was 33 feet 3 inches, height was 14 feet 2 inches, and wing area was 300 square feet.
From
http://www.geocities.com/pentagon/qu...485/P-47M.html :
The "J" was fitted with a high output version of the P&W R-2800. Specifically, the R-2800-57. This engine made 2,800 hp @ 2,800 rpm at 35,000 feet. This is in War Emergency Power.
The aircraft actually attained 507 mph at an altitude of 34,300 feet. 2,800 hp is 133% of rated power. At military power (100%), the XP-47J could sustain 470 mph. 435 mph was attained at 81% of its rated power (1,700 hp). All performance figures were obtained at 34,300 feet.
The "J" model was an especially good climbing fighter too. It had a climb rate at sea level of 4,900 fpm. At 20,000 feet, it was still rocketing up at 4,400 fpm, and got there in 4 minutes, 15 seconds. Time to 30,000 feet was only 6 minutes, 45 seconds. Now that's an interceptor! Yet it had a usable range of 1,075 miles. Rather impressive, don't you think? No, this was not a stripped down hotrod. It was fully armed and carried ballast in the wings equal to 267 rds per gun. The aircraft was flown to a height of 46,500 feet and was capable of a bit more.
Republic XP-72 Superbolt http://www.warbirdsresourcegroup.org...ges/xp72-2.jpg http://www.wpafb.af.mil/museum/research/p72-2.jpg
Specific ation of Republic XP-72:
Powerplant: One 3450 hp Pratt & Whitney R-4360-13 Wasp Major air-cooled radial engine.
Performance: Maximum speed was 490 mph at 25,000 feet. Normal range was 1200 miles at 300 mph and maximum range was 2520 miles at 315 mph with two 125 Imp. gall. drop tanks. Initial climb rate was 5280 feet per minute, and climb rate at 25,000 feet was 3550 feet per minute. An altitude of 15,000 feet could be reached in 3.5 minutes, 20,000 feet in 5 minutes. Service ceiling was 42,000 feet.
Weights were 11,476 pounds empty, 14,433 pounds normal loaded, 17,490 pounds maximum.
Dimensions were wingspan 40 feet 11 inches, length 36 feet 7 inches, height 16 feet 0 inches, and wing area 300 square feet.
Armament: Four 37mm cannon.
Lockheed P-80 Shooting Star http://www.daveswarbirds.com/usplane...t/shootstr.htm 
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