In 1943, two P-47D-15-RE airframes [42-23297/23298] were selected for testing with the experimental 16-cylinder 2300hp Chrysler XIV-2220-1 inverted Vee, liquid-cooled engine and were redesignated XP-47H. The Chrysler with its large under-fuselage radiator radically changed the appearance of the Thunderbolt and increased overall length to 39'2". With the increased power and improved streamlining, a maximum speed of 490 mph was envisioned.
Although the project was begun in Aug 1943, the two airframes were not actually converted until 1945. Test flights began July 26, 1945. One of my sources (Green) says that, during flight trails, one of the planes actually attained a speed of 490 mph in level flight. However, another one (Wagner) says that the Chrysler engine failed to deliver promised power output and that top speed attained in tests was only 414 mph at 30,000', poorer performance than a stock P-47D. Whichever case, the engine never achieved production, and the advent of jet propulsion killed any further AAF interest in developing piston-engined fighters. Consequently, work on the project ended.
The fastest version of the Thunderbolt was the XP-47J, proposed in Nov 1942 as a lighter-weight version o explore the outer limits of the design's basic performance envelope. It had a 2800hp P&W R-2800-57(C) housed in a close-fitting cowling and cooled by a fan. The ventral intake for the CH-5 turbo-supercharger was separated from the engine cowling and moved aft, the four-blade propeller had a large conical-shaped spinner, and the wing structure was lightened. Armament was reduced from to six 0.50-inch machine guns. A contract was approved on June 18, 1943.
The XP-47J was not a conversion of an existing P-47, but a completely new airframe [43-46952]. It flew for the first time on Nov 26, 1943 and, on Aug 4, 1944, reached 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 be introduced onto the production line, but the advent of the even more advanced XP-72 resulted in plans for the production being abandoned before any more could be completed.
A subsequent proposal to modify the XP-47J to use contrarotating propellers with an R-2800-61 engine was dropped.
P-47D fuselage [42-8702] modified with a bubble canopy from an RAF Hawker Typhoon. Tested in July 1943.
P-47D [42-76614] modified with a bubble canopy and larger fuel tanks.
The P-47M was a special high-speed version specifically evolved to counter the buzz-bomb and the new jet- and rocket-powered fighters that were entering service with the Luftwaffe. Four P-47D-27 airframes were taken off the production line at Farmingdale and fitted with the P&W R-2800-57(C) equipped with a larger CH-5 turbo-supercharger. The new engine offered a war-emergency power of 2800hp at 32,500' with water injection and had air brakes under the wings to aid in deceleration during dives. Those four were redesignated YP-47M prototypes.
The engine installations then went into production in Sep 1944 for the last 130 P-47D-30 Farmingdale aircraft, which were subsequently redesignated P-47M-1-RE. Underwing racks were not fitted, as they were intended to be fighters only. First delivery was in Dec 1944, and they were rushed to the 56th FG in England, but engine problems delayed their use until the last few weeks of the war in Europe.
POP: 4 YP-47M [42-27385/27388]
POP: 130 P-47M-1-RE [44-21108/21237].
The last of the Thunderbolts to be manufactured in quantity was the P-47N, a specialized long-range version designed specifically for service in the Pacific theatre. However, the war there required fighter ranges even greater than over Germany. In pursuit of better long-range performance, in mid-1944 the third YP-47M prototype [42-27387] received a new "wet" wing of slightly larger span and area and was redesignated XP-47N. For the first time a Thunderbolt carried fuel in its wings, a 93-gal tank in each one. When maximum external tankage was carried, that brought its total fuel load up to an impressive 1,266 gallons, which made possible a range of 2,350 miles.
The new wing also incorporated larger ailerons and squared-off wingtips, innovations that enhanced roll-rate and improved maneuverability. The dorsal fin behind the bubble canopy was somewhat larger than that on the P-47D. However, increased fuel load increased the gross weight, so to cope with that, the undercarriage of the XP-47N had to be strengthened, which increased the weight even more, to over 20,000#.
Such was the confidence in the Thunderbolt design that the AAF ordered 1,900 P-47Ns on June 20, a month before the XP-47N's first flight, on July 22.
The first P-47N-1-RE appeared in Sept of 1944, and 24 were delivered by year's end. P-47N-5-RE and subsequent batches had zero-length rocket launchers added and the P&W R-2800-77 was installed in late production models, such as the P-47N-25-RE.
The P-47N gave excellent service in the Pacific in the final year of the war, particularly in escorting B-29 bombers in raids on the Japanese mainland. They were able to escort bombers all the way from Saipan to Japan and on many other long overwater flights.
A total of 1,667 P-47Ns was produced at the Farmingdale plant between Dec 1944 and Dec 1945, when the Thunderbolt line finally closed down. 149 more were built at the Evansville factory. V-J Day cancellation of 5,934 Thunderbolts brought production of the type abruptly to an end.
POP: 1 XP-47N [42-27387].
POP: 550 P-47N-1-RE [44-87784/88333]; 550 P-47N-5-RE [44-88334/88883]; 200 P-47N-15-RE [44-88884/89083]; 200 P-47N-20-RE [44-89084/89283]; 167 P-47N-25-RE [44-89284/89450].
POP: 149 P-47N-20-RA [45-49975/50123].
SOURCES as previous.