The Republic P-47 Thunderbolt (nicknamed the "Jug") is a monoplane fighter aircraft designed and produced by the American aircraft manufacturer Republic Aviation. Designed around the powerful Pratt & Whitney R-2800 Double Wasp 18-cylinder radial engine and produced from 1941 through to 1945, it became the foremost American fighter-bomber in the ground-attack role during World War II. When fully loaded, the P-47 weighed up to eight tons, making it one of the heaviest fighters of the conflict. It is the namesake of a later U.S. ground-attack aircraft, the Fairchild Republic A-10 Thunderbolt II.
The origins of the P-47 can be traced back to the late 1930s and the work of Alexander Kartveli, who sought to develop a replacement for the Seversky P-35. The resulting AP-10 fighter design attracted the backing of the United States Army Air Corps (USAAC), which designated it XP-47. Subsequent revisions to keep pace with contemporary fighters of other nations led to the XP-47B, a prototype of which was ordered in September 1940 and performed its maiden flight on 6 May 1941. The P-47 was noted for its firepower; its primary armament was eight .50-caliber machine guns, and it could carry 5-inch rockets or a bomb load of . It was also noted for its ability to remain airworthy with battle damage. The P-47's R-2800 engine, which also powered the U.S. Navy/U.S. Marine Corps Grumman F6F Hellcat and Vought F4U Corsair, used a turbocharger, which ensured the aircraft's eventual dominance at high altitudes, while also influencing its size and design. The armored cockpit was relatively roomy and comfortable, while the sliding bubble canopy introduced on the P-47D offered good visibility.
In December 1941, the first production P-47 was delivered to the recently created United States Army Air Forces (USAAF); roughly one year later, P-47Cs were sent to England for combat operations under the 8th Air Force. It found success in the both European and Pacific theaters as an escort fighter, well-suited to high-altitude air-to-air combat. The P-47 was able to accompany Allied bombers all the way into Germany and perform their own attacks against ground targets of opportunity on the return journey. When operated in tandem with Supermarine Spitfires, they proved devastating against Japanese forces during the Battle of the Sittang Bend. Two P-47 pilots, Neel E. Kearby and Raymond L. Knight, received the Medal of Honor. By the end of the conflict, the P-47 had become one of the USAAF's primary fighter-bombers; between D-Day and VE day alone, P-47 pilots claimed to have destroyed roughly 86,000 railroad cars, 9,000 locomotives, 6,000 armored fighting vehicles, and 68,000 trucks.
In addition to the USAAF, the P-47 also served with the air forces of France, the United Kingdom, and the Soviet Union, and with Allied Mexican and Brazilian squadrons. While production of the type was terminated shortly after the end of WWII, the P-47 continued to be widely operated into the Cold War era; while considered to be obsolete as a fighter by the late 1950s, it proved to be a good match for counterinsurgency operations. France deployed its P-47s during the Algerian War of Independence, while both the Chinese Nationalists and Chinese Communists flew P-47s during the Chinese Civil War. Several aircraft have been preserved into the 21st century.
Development
The P-47 Thunderbolt was designed by Alexander Kartveli, an aeronautical engineer of Georgian descent. It was developed to replace the Seversky P-35, which had previously developed by Russian immigrant Alexander P. de Seversky; Both Kartveli and de Seversky had fled from their homeland of Georgia to escape the Bolsheviks. In 1939, Republic Aviation designed the AP-4 demonstrator powered by a Pratt & Whitney R-1830 radial engine with a belly-mounted turbocharger. While a small number of Republic P-43 Lancers were built, Republic had been working on an improved P-44 Rocket with a more powerful engine, as well as on the AP-10 fighter design. The latter was a lightweight aircraft powered by the Allison V-1710 liquid-cooled V-12 engine and armed with two .50 in (12.7 mm) M2 Browning machine guns mounted in the nose and four .30 in (7.62 mm) M1919 Browning machine guns mounted in the wings. The United States Army Air Corps (USAAC) backed the project and gave it the designation XP-47.
In the spring of 1940, Republic and the USAAC concluded that both the XP-44 and the XP-47 were inferior to contemporary Luftwaffe fighters.Freidman December 1942, p. 112. Republic tried to improve the design, proposing the XP-47A, but this was not received well. Thereafter, Kartveli designed a substantially larger fighter that when offered to the USAAC in June 1940, was met with an order for a prototype in September of that year as the XP-47B.Freidman December 1942, pp. 112-113, 226. The XP-47A, which had little in common with the new design, was abandoned. The XP-47B was of all-metal construction (except for the fabric-covered flight control surfaces on the tail), with elliptical wings whose straight leading edge was slightly swept back. The P-47's airfoil section was developed by Kartveli and was designated as Republic S-3.
The cockpit was relatively spacious and provisioned with air conditioning and a comfortable seat for the pilot — "like a lounge chair", as one pilot put it. To aid the pilot, it was provisioned with automatic controls.Freidman December 1942, p. 109. The canopy door initially hinged upward. Both the main and auxiliary self-sealing fuel tanks were located under the cockpit, providing for a total fuel capacity of .
It was powered by a Pratt & Whitney R-2800 Double Wasp two-row, 18-cylinder radial engine, capable of producing up to ,Freidman December 1942, p. 108. that drove a four-bladed Curtiss Electric constant-speed propeller of in diameter. The loss of the AP-4 prototype to an engine fire ended Kartveli's experiments with tight-fitting cowlings, so the engine was placed in a broad cowling that opened at the front in a "horse collar"-shaped ellipse. This cowling admitted cooling air for the engine, left and right oil coolers, and the turbosupercharger intercooler system. The engine exhaust gases were routed into a pair of wastegate-equipped pipes that ran along each side of the cockpit to drive the turbosupercharger turbine at the bottom of the fuselage, about halfway between cockpit and tail. At full power, the pipes glowed red at their forward ends and the turbine spun at 21,300 rpm."The Turbosupercharger and the Airplane Power Plant." General Electric, January 1943.
The complicated turbosupercharger system with its ductwork took up roughly half of the fuselage's internal volume, thus determined the shape of several key areas of the aircraft, such as the mounting of the wings in a relatively high position.Freidman December 1942, pp. 110, 228. This arrangement posed some difficulty relating to the landing gear, which needed relatively long-legged struts to provide sufficient ground clearance for the aircraft's relatively large propeller. To reduce the size and weight of the undercarriage struts, as well as to permit the fitting of wing-mounted machine guns, each strut was fitted with a mechanism by which it telescoped out while it extended. While widely spaced, the landing gear reportedly possessed favorable characteristics even over rough terrain.Freidman December 1942, p. 110.
The XP-47B, in comparison to contemporary single-engined fighters, was a relatively heavy aircraft.Freidman December 1942, p. 228. It possessed an empty weight of , which was 65% more than the YP-43. Kartveli stated: "It will be a dinosaur, but it will be a dinosaur with good proportions". The armament comprised eight .50-caliber (12.7 mm) "light-barrel" Browning AN/M2 machine guns, four in each wing. These guns were staggered to allow feeding from side-by-side ammunition boxes, each with 350 rounds. All eight guns gave the fighter a combined rate of fire around 100 rounds per second.Masefield, Peter. "First Analysis of the Thunderbolt." Flying, August 1943, p. 190.Freidman December 1942, pp. 110-112.
On 6 May 1941, the XP-47B conducted its maiden flight with Lowry P. Brabham at the controls.Freidman December 1942, p. 226. Although minor problems arose, such as some cockpit smoke that turned out to be due to an oil drip, the aircraft demonstrated impressive performance during its early trials. The prototype was lost in an accident on 8 August 1942, but before that mishap, it had achieved a level speed of at altitude and had demonstrated a climb from sea level to in five minutes.Green 1961, p. 173.
The performance of the XP-47B had been sufficiently convincing that in August 1941, the newly reorganized United States Army Air Forces (USAAF) placed an order for 171 production aircraft,Freidman December 1942, p. 226. the first of which was delivered in December 1941.
Operational history US
By the end of 1942, P-47Cs were sent to England for combat operations. The initial Thunderbolt flyers, 56th Fighter Group, were sent overseas to join the 8th Air Force. As the P-47 worked up to operational status, it gained a nickname: "Jug" (because its profile was similar to that of a common milk jug of the time). Two fighter groups already stationed in England began introducing the P-47 in January 1943 - the Spitfire-flying 4th Fighter Group, a unit built around a core of experienced American pilots who had flown in the RAF Eagle Squadrons prior to the US entry in the war; and the 78th Fighter Group, formerly flying P-38 Lightnings. The first P-47 combat mission took place on 10 March 1943, when the 4th FG took their aircraft on a fighter sweep over France. The mission was a failure due to radio malfunctions. Accordingly, all P-47s were refitted with British radios, and missions resumed on 8 April. The first P-47 air combat took place on 15 April with Major Don Blakeslee of the 4th FG scoring the Thunderbolt's first air victory (against a Focke-Wulf Fw 190).
Beginning in January 1943, P-47s were sent to the joint USAAF–civilian Millville Airport in Millville, New Jersey, to train civilian and military pilots.
During late 1943, the type started flying with the 12th Air Force, stationed in North Africa, initially intended to serve as a high-altitude interceptor.Bernstein 2012, p. 8. The P-47's capabilities permitted not only effective escorting of Allied bombers, but also conducting interdiction and maritime reconnaissance over the Adriatic Sea. The type's ordinance capacity proved to be particularly useful when conducting antishipping missions.Bernstein 2012, pp. 8-9, 12.
Furthermore, P-47s were used against the Japanese in the Pacific, such as with the 348th Fighter Group flying missions out of Port Moresby, New Guinea. By 1944, the USAAF was operating the Thunderbolt in combat across all of its operational theaters except Alaska.
With increases in fuel capacity as the type was refined, the range of escort missions over Europe steadily increased until the P-47 was able to accompany bombers in raids all the way into Germany. On the way back from the raids, pilots shot up ground targets of opportunity, and also used belly shackles to carry bombs on short-range missions, which led to the realization that the P-47 could perform a dual function on escort missions as a fighter-bomber. Even with its complicated turbosupercharger system, its sturdy airframe and tough radial engine could absorb significant damage and still return home.