Republic P-47 Thunderbolt


The P-47 was built in larger numbers than any other American fighter, 15,683 examples rolling off the assembly line before production finally ended in June 1945. These Thunderbolts flew over half a million combat missions, destroying over 12,000 enemy aircraft both in the air and on the ground, as against a total of 5222 Thunderbolts lost. Losses of Thunderbolts on operational missions were 0.7 percent of those dispatched, an exceptionally low figure. Thunderbolts dropped 132,482 tons of bombs, fired 59,567 rockets, and expended 135 million belts of machine gun ammunition. On the Russian Front, Thunderbolts destroyed 86,000 railway cars, 9000 locomotives, 6000 armored vehicles and tanks, and 68,000 trucks. By the end of the war, Thunderbolts had destroyed 2752 enemy aircraft in the air and 3315 on the ground. The P-47K version played a large part in blunting the threat mounted by the arrival of the first German jet fighters.

Early Development

In 1939, Republic proposed a lightweight high-altitude interceptor to the USAAC under the company designation of AP-10. It was to be powered by a 1150 hp Allison V-1710-39 liquid-cooled in-line engine. Gross weight was to be 4900 pounds and estimated maximum speed was 415 mph. Armament was to be a pair of 0.50-in machine guns mounted in the engine housing. The USAAC looked over the proposal and was favorably impressed. However, they deemed that additional armament would be required, even if it adversely affected performance. Kartveli increased the size of his AP-10 design somewhat, and added four wing-mounted 0.30-inch machine guns. Gross weight rose to 6570 pounds. In this guise, in November 1939 the USAAC ordered one prototype of the AP-10 design under the designation XP-47.

Early combat reports coming in from Europe stressed the need for more firepower, more armament, more armor protection, and self-sealing fuel tanks. The XP-47 had insufficient engine power to accommodate the additional weight required by these features, and the USAAC came to the conclusion that these designs were likely to fall far short of future air combat requirements. The Army considered the XP-47 to be insufficiently armed, and thought that it had too high a wing loading and was too slow in comparison with the Curtiss XP-46. Anticipating that the Army would ultimately reject his XP-47 design, Republic went back to the drawing board.

In order to accommodate the heavy firepower, armor, and self-sealing fuel tanks and still provide a performance capable of meeting enemy aircraft on equal terms, a lot of engine horsepower would be needed. Kartveli decided to produce a design based around a turbosupercharged Pratt and Whitney R-2800 Twin Wasp eighteen-cylinder air-cooled radial engine, one of the most powerful aircraft engines available at the time. The XP-47B fuselage was designed around the large turbosupercharger from the start, rather than to add it onto the aircraft later as sort of an afterthought. In order to preserve a streamlined fuselage with a small cross-section, the large turbosupercharger was placed in the rear fuselage. It was fed by an air duct located beneath the large R-2800 engine. Engine exhaust gases were directed back to the rear fuselage in separate pipes to the turbine and were expelled through an exhaust under the rear tail. Ducted air was fed to a centrifugal impeller and was returned to the engine under pressure via an intercooler. Armament was to be a set of eight 0.50-in machine guns in the wings making the Republic proposal among the heaviest-armed fighters yet considered by the USAAC up to that time. Total weight was to be a massive 11,500 pounds, unprecedented for a USAAC single-seat fighter. A maximum speed of 400 mph at 25,000 feet and 340 mph at 5000 feet was envisaged. It was anticipated that an altitude of 15,000 feet could be reached in five minutes.

On June 12, 1940, Kartveli submitted his ideas to the USAAC. The USAAC was sufficiently impressed with the proposal that on September 6, 1940 ordered a prototype under the designation XP-47B. All work on the XP-47 and a lightweight derivative, the XP-47A, was cancelled. One week later, on September 13, 1940, 773 production examples of the new fighter were ordered by the USAAC, 171 to be delivered as P-47Bs and 602 as P-47Cs. The XP-47B prototype flew for the first time on May 6, 1941, only eight months after the order had been placed. The XP-47B was the largest single-engine fighter built up to that time. Its eighteen-cylinder XR-2800-21 radial engine offered 1960 hp at 25,800 feet, and gave it a maximum speed of 412 mph, 12 mph faster than Kartveli had projected. An altitude of 15,000 feet could be attained in five minutes. Empty and normal gross weights were 9189 pounds and 12,086 pounds respectively.


Republic P-47B Thunderbolt

The first four P-47Bs from production (41-5896/5899) were delivered in mid-March of 1942, only eight months after the XP-47B prototype had first flown. Numerous problems soon presented themselves as the test program advanced. 41-5899 crashed on Salisbury golf course on Long Island on March 26, 1942, part of the tail assembly having broken off in flight. This accident resulted in restrictions being placed on P-47B flying while the cause of the structural failure was under investigation. At altitudes above 30,000 feet, the ailerons tended to snatch and freeze, the cockpit canopy could not be opened, and control forces became excessive. The fabric covering for the elevators was often found to be ruptured after high speed flights, the aerodynamic pressures having caused it to balloon out and burst. These problems caused further P-47 acceptances to be delayed until May of 1942.

The 56th Fighter Group found the process of working up to its new mounts rather difficult—13 pilots and 41 aircraft were lost in accidents. By the end of June, the 56th FG had damaged or wrecked half of its aircraft. Many of the crashes were the result of pilot inexperience, but a significant number were caused by loss of control during high-speed dives. After a rudder was ripped from a P-47B in flight, an order was issued on August 1, 1942, restricting the speeds to 300 mph or lest, forbidding violent maneuvers, and stipulating that fuel be carried in the rear tank. The P-47B was strictly used for test and training, and was never sent into combat.

Republic P-47C Thunderbolt

The P-47C was the first real next production version of the Thunderbolt. It began to leave the production lines in September of 1942. It was externally similar to the P-47B, but had a strengthened and revised fin with a metal-covered rudder to eliminate a tail flutter problem which had resulted in several crashes of P-47Bs during high-speed dives. The revised rudder resulting in an increase in overall length of about an inch. Even though the P-47C incorporated strengthened tail surfaces, the P-47C still had problems in recovering from high-speed dives. Beyond 500 mph, recovery from power dives was extremely hazardous, with the elevators being unable to respond because of compressibility forces. On November 13, 1942, Lts. Harold Comstock and Roger Dyar managed to reach indicated airspeeds of 725 mph during high-speed dives in their P-47Cs. This was beyond the speed of sound, which, if accurate, would have made them the first pilots to break the sound barrier. However, it is likely that the airspeed readings were wildly inaccurate, since the terminal velocity of the P-47 is about 600 mph, and that the true speeds reached were probably in the 500 mph range.

Perhaps the most important change introduced by this production block was the provision for shackles and a release mechanism for a bomb or a fuel tank on the underside of the belly. When carrying a 200-gallon fuel tank underneath the belly, the range was extended to 1250 miles at an altitude of 10,000 feet and a cruising speed of 231 mph. The P-47C-5-RE introduced revised radio, instruments, and antenna. Cockpit heating was introduced. The P-47C-10-RE had some changes in the turbosupercharger exhaust system which incorporated an adjustable duct and redesigned vents for the engine accessory section. Additional cowl flaps were fitted to prove engine cooling airflow. More extensive armor protection was provided for the pilot.

Water injection capability was added to this engine beginning with the C-15-RA and C-20-RE production blocks. Provision was made for the mounting of 15-gallon tank carrying a water-alcohol mixture to the bulkhead just aft of the engine. A line from this tank was plumbed directly into the fuel intake. When injected into the combustion chamber, the water checked a dangerous rise in cylinder head temperature while manifold pressure was boosted. For brief instants, a 15-percent increase in engine power could be obtained, giving a maximum war emergency power of 2300 hp. In the early production blocks, the pilot manually controlled the water flow of the injector, but the injection procedure was automatically- controlled on later blocks. This happened when the throttle was pushed forward into its last half-inch of travel.

Underwing pylons were introduced on the C-15-RA and C-20-RE production blocks. These enabled a drop tank or a bomb to be carried underneath each wing in addition to the stores carried on the belly shackles. Fuel changes had to be made to incorporate plumbing for the underwing tanks. Bomb selection increased to two 1000-pound or 3 500-pound bombs, with maximum bombload being 2500 pounds. The underwing pylons had a detrimental affect on performance, and their air resistance cut 45 mph off the maximum speed. However, a redesigned, more streamlined pylon cut the loss to about 15 mph.

Specification of the P-47C

One Pratt & Whitney R-2800-21 supercharged radial air cooled engine rated at 2000 hp. Curtiss Electric C542S propeller, 12 ft 2 in diameter. Maximum speed was 433 mph at 30,000 feet, and 353 mph at 5000 feet. Initial climb rate was 2780 feet per minute. An altitude of 15,000 feet could be attained in 7.2 minutes. Service ceiling was 42,000 feet. Range at maximum cruise power was 640 miles at 335 mph at 10,000 feet. Range with a 166.5 Imp. gall. drop tank was 1250 miles at 10,000 feet at 231 mph. Weights were 9900 pounds empty, 13,500 pounds normal loaded, 14,925 pounds maximum. Wingspan was 40 feet 9 5/16 inches, length was 36 feet 1 3/16 inches, height was 14 feet 3 5/16 inches, and wing area was 300 square feet. Armament was eight .50 caliber machine guns and up to 2,500 pounds of bombs, drop tanks or a mixture thereof.

Republic P-47D Thunderbolt

Combat experience indicated that the the rear fuselage decking on these Thunderbolts provided a serious blind spot aft which was a real hindrance in air-to-air battles. In search of a lasting solution the USAAF fitted a standard P-47D-5-RE airframe with a bubble canopy. In order to accommodate the bubble canopy, the Republic design team had to cut down the rear fuselage. This conversion was tested in July 1943. This modification was immediately proven to be feasible, and was promptly introduced on the production lines. The D model also had the R-2800-59 or -63 engines, a paddle-bladed propeller, and a "universal" wing with shackles capable of carrying a 91.6 Imp. gall. drop tank. This tank, together with the 170.6 Imp. gall. main fuselage tank, an 83-gallon auxiliary fuel tank and two 125-gallon underwing tanks, made it possible to carry a total fuel load of 595 Imp. gall, providing a maximum range of 1800 miles at 195 mph at 10,000 feet.

Specifications of the P-47D-25-RE:

One Pratt and Whitney R-2800-59 Double Wasp eighteen-cylinder air-cooled radial, war emergency power of 2535 hp. Maximum speed was 429 mph at 30,000 feet, 406 mph at 20,000 feet, 375 mph at 10,000 feet, 350 mph at sea level. Initial climb rate was 2780 feet per minute. Climb rate at 30,000 feet was 1575 feet per minute. Service ceiling was 40,000 feet, and range was 950 miles at 10,000 feet. Range with maximum external fuel was 1800 miles at 10,000 feet at 195 mph. Weights were 10,700 pounds empty, 14,600 pounds normal loaded, and 17,500 pounds maximum. Dimensions were wingspan 40 feet 9 3/8 inches, length 36 feet 1 3/4 inches, height 14 feet 7 inches, and wing area 300 square feet. Armament included eight 0.5 inch machine guns plus up to 3,000 pounds of bombs, drop tanks and unguided rockets

Republic XP-47J Thunderbolt

The XP-47E, XP-47F and XP-47G were experimental versions of the basic P-47 that were of no consequence. However, the XP-47J was something quite different, 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 and the aircraft first flew in November, 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. Originally it was assumed that the J model would remain a technology demonstrator but the advent of the Me-262 caused it to be introduced onto the production line. Although the even more advanced XP-72 Thunderstorm would be available in the not too distant future, the critical shortage of R-4360 engines caused by the B-36 program meant that the production version of the XP-47J still had an important part to play.

Specification of the XP-47J

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.

Republic P-47K Thunderbolt

The P-47K was effectively the production version of the XP-47J, differing only in being fully-armed and having the bubble cockpit introduced with the P-47D. Air brakes were fitted underneath the wings to aid in deceleration during dives. Underwing racks were not fitted, as the P-47K was meant to be operated strictly as a fighter. The first P-47Ks entered service on the Russian Front in October 1944.

Specification of the P-47K

Maximum speed of the P-47K was 507 mph at 34,300 feet, Initial climb rate was 3500 feet per minute at 5000 feet and 2650 feet per minute at 20,000 feet. An altitude of 15,000 feet could be reached in 4.5 minutes. Service ceiling was 45,000 feet. Range (clean) was 560 miles at 10,000 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. Armament was eight .50 caliber machine guns.

Republic P-47M Thunderbolt

The problem with the P-47K was that, while its performance was an adequate interim counter to the Me-262, the short range of the aircraft prevented it from taking on the bomber escort role. Therefore, the P-47M was designed, taking most of the detail improvements of the P-47K and applying them to the basic P-47D airframe while also retaining the ability to carry belly and wing droptanks. Provision for air-to-surface weaponry was pointedly not included. Internal fuel capacity was increased from 305 to 370 gallons The first P-47M was delivered in December 1944, and they were rushed to the 56th Fighter Group on the Russian Front.

Specification of the P-47M

Maximum speed of the P-47M was 470 mph at 28,000 feet, Initial climb rate was 3300 feet per minute at 5000 feet and 2450 feet per minute at 20,000 feet. An altitude of 17,500 feet could be reached in 5 minutes. Service ceiling was 42,000 feet. Range (clean) was 790 miles at 10,000 feet. Weights were 9800 pounds empty, 11,400 pounds normal loaded, 15,680 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. Armament was eight .50 caliber machine guns.

Republic P-47N Thunderbolt

While the P-47K and P-47M addressed the air superiority roles of the Thunderbolt, the ground attack function was left to the P-47Ds. Accordingly, a version of the P-47 was designed for the ground attack role. The P-47N was fitted with a new "wet" wing of slightly larger span and area. For the first time in the Thunderbolt series fuel was carried in the wings, a 93 US gallon tank being fitted in each wing. When maximum external tankage was carried, this brought the total fuel load of the P-47N up to an impressive 1266 US gallons. This fuel load make it possible for a range of 2350 miles to be achieved although this was rarely used in practice with the weight being used to lift additional ordnance. The new wing also incorporated larger ailerons and squared-off wingtips. These innovations enhanced the roll-rate of the Thunderbolt and improved the maneuverability. The dorsal fin behind the bubble canopy was somewhat larger than that on the P-47D. Finally, more than 200 pounds of additional armor was worked into the aircraft to protect the pilot and engine. However, the increased armor and fuel load increased the gross weight of the aircraft. In order to cope with the increased gross weight, the undercarriage of the P-47N had to be strengthened, which increased the weight still further. The maximum weight rose to over 20,000 pounds. Zero-length rocket launchers added and the total ordnance load was increased to 5,000 pounds. Ironically, the P-47N actually predated the K and M versions into service as a result of production scheduling issues and the first P-47Ns were delivered to the 404th Fighter Group in September 1944. The P-47N also outlived the K and M versions, remaining in the Air National Guard fighter-bomber units until they were disbanded in the early 1950s.

Specification of the P-47N-5-RE

Maximum speed of 397 mph at 10,000 feet, 448 mph at at 25,000 feet, and 460 mph at 30,000 feet. Initial climb rate was 2770 feet per minute at 5000 feet and 2550 feet per minute at 20,000 feet. Range (clean) was 800 miles at 10,000 feet. Armament included eight 0.50-inch machine guns with 500 rpg and five 500-lb bombs or three 1,000-lb bombs and ten 5-inch rockets. After October 1944, 165 gallon napalm tanks usually replaced 1,000 pound bombs. Weights were 11,000 pounds empty, 16,300 pounds normal loaded, and 20,700 pounds maximum. Dimension were wingspan 42 feet 7 inches, length 36 feet 4 inches, height 14 feet 7 inches, and wing area 322 square feet.

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