The Republic P-47 Thunderbolt was the largest, heaviest, and most expensive fighter aircraft in history to be powered by a Radial Piston Engine. It was heavily armed with eight .50-caliber machine guns, four per wing. When fully loaded, the P-47 weighed up to eight tons, and in the fighter-bomber ground-attack roles could carry five-inch rockets or a significant bomb load of 2,500 pounds; it could carry over half the payload of the B-17 bomber on long-range missions (although the B-17 had a far greater range). The P-47, based on the powerful Pratt & Whitney R-2800 Double Wasp engine, was to be very effective as a short-to-medium range escort fighter in high-altitude air-to-air combat and, when unleashed as a fighter-bomber, proved especially adept at ground attack in both the World War II European and Pacific Theaters.
The P-47 was one of the main United States Army Air Forces (USAAF) fighters of World War II, and served with other Allied air forces, notably those of France, Britain, and Russia. Mexican and Brazilian squadrons fighting alongside the U.S. were equipped with the P-47.
The armored cockpit was roomy inside, comfortable for the pilot, and offered good visibility. A modern-day U.S. ground-attack aircraft, the Fairchild Republic A-10 Thunderbolt II, takes its name from the P-47.
The P-47 Thunderbolt was a design of Georgian immigrant Alexander Kartveli, and was to replace the Seversky P-35 that was developed earlier by Russian immigrant Alexander P. de Seversky born in the same place as Kartveli: Tbilisi, Georgia. Both had left their homeland 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 the resulting Republic P-43 Lancer was in limited production, Republic had been working on an improved P-44 Rocket with a more powerful engine, as well as on a fighter designated the AP-10. The latter was a lightweight aircraft powered by the Allison V-1710 liquid-cooled V-12 engine and armed with eight .50 in M2 Browning machine guns. The United States Army Air Corps (USAAC) backed the project and gave it the designation XP-47.
As the war in Europe escalated in spring 1940, Republic and the USAAC concluded that the XP-44 and the XP-47 were inferior to the German fighters. Republic unsuccessfully attempted to improve the design, proposing the XP-47A. Kartveli subsequently came up with an all-new and much larger fighter which was offered to the USAAC in June 1940. The Air Corps ordered a prototype in September, to be designated the XP-47B. The XP-47A, which had almost nothing in common with the new design, was abandoned.
The XP-47B was of all-metal construction (except for the fabric-covered tail control surfaces) with elliptical wings, with a straight leading edge that was slightly swept back. The cockpit was roomy and the pilot’s seat was comfortable—”like a lounge chair”, as one pilot later put it. The pilot was provided with every convenience, including cabin air conditioning. The canopy doors hinged upward. Main and auxiliary self-sealing fuel tanks were placed under the cockpit, giving a total fuel capacity of 305 U.S. gal .
Power came from a Pratt & Whitney R-2800 Double Wasp two-row 18-cylinder radial engine producing 2,000 hp , the same engine that would power the prototype Vought XF4U-1 fighter in October 1940 – with the Double Wasp on the XP-47B turning a four-bladed Curtiss electric constant-speed propeller of 146 in, 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. The cowling admitted cooling air for the engine, left and right oil coolers, and the turbo supercharger intercooler system. The engine exhaust gases were routed into a pair of waste gate-equipped pipes that ran along each side of the cockpit to drive the turbo supercharger 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 complicated turbo supercharger system with its ductwork gave the XP-47B a deep fuselage, and the wings had to be mounted in a relatively high position. This was problematic since long landing gear was needed to provide ground clearance for the propeller. To reduce the size and weight of the long landing gear and so that wing-mounted machine guns could be fitted, each main gear strut was fitted with a mechanism by which it telescoped out 9 in when extended.
The XP-47B was a very large aircraft for its time with an empty weight of 9,900 lb., or 65% more than the YP-43. Kartveli is said to have remarked, “It will be a dinosaur, but it will be a dinosaur with good proportions. The armament consisted of eight .50 caliber “light-barrel “Browning AN/M2 machine guns, four in each wing. The guns were staggered to allow feeding from side-by-side ammunition boxes, each with a 350-round capacity. Although the British already possessed eight-gun fighters, the Hurricane and the Spitfire, and even the 12-gun Typhoon, they used smaller-caliber 0.303 in machine guns.
The XP-47B first flew on 6 May 1941 with Lowry P. Brabham at the controls. Although there were minor problems, such as some cockpit smoke that turned out to be due to an oil drip, the aircraft proved impressive in its first trials. It was eventually lost in an accident on 8 August 1942, but before that mishap, the prototype had achieved a level speed of 412 mph at 25,800 ft. altitude, and had demonstrated a climb from sea level to 15,000 ft. altitude in five minutes.
All the P-47s produced to this point had a “razorback” canopy configuration with a tall fuselage spine behind the pilot, which resulted in poor visibility to the rear. The British also had this problem with their fighter aircraft, and had devised the bulged “Malcolm hood” canopy for the Spitfire as an initial solution. This type of canopy was fitted in the field to many North American P-51 Mustangs, and to a handful of P-47Ds (and far more on P-47Bs and P-47Cs). However, the British then came up with a much better solution, devising an all-round vision “bubble canopy” for the Hawker Typhoon. USAAF officials liked the bubble canopy, and quickly adapted it to American fighters, including the P-51 and the Thunderbolt. The first P-47 with a bubble canopy was a modified P-47D-5 completed in the summer of 1943 and redesignated XP-47K. Another older P-47D was modified to provide an internal fuel capacity of 370 U.S. gal and given the designation-47L. The bubble canopy and increased fuel capacity were then rolled into production together, resulting in the block 25 P-47D (rather than a new variant designation). First deliveries to combat groups began in May 1944.
It was followed by similar bubble-top variants, including the P-47D-26, D-27, D-28 and D-30. Improvements added in this series included engine refinements, more internal fuel capacity, and the addition of dive recovery flaps. Cutting down the rear fuselage to accommodate the bubble canopy produced yaw instability, and the P-47D-40 introduced a dorsal fin extension in the form of a narrow triangle running from the vertical tail plane to the radio aerial. The fin fillet was retrofitted in the field to earlier P-47D bubble-top variants. The P-47D-40 also featured provisions for 10 “zero length” stub launchers for 5 in High velocity aircraft rockets (HVARs), as well as the new K-14 computing gun sight. This was a license-built copy of the British Ferranti GGS Mark IID computing gyroscopic sight which allowed the pilot to dial in target wingspan and range, and would then move the gun sight reticle to compensate for the required deflection.
The bubbletop P-47s were nicknamed “super bolts” by combat pilots in the field.
Two XP-47Hs were built. They were major reworking’s of existing razorback P-47Ds to accommodate a Chrysler IV-2220-11 water-cooled 16-cylinder inverted v engine. However, such large inline engines did not prove to be especially effective.
The XP-47J began as a November 1942 request to Republic for a high-performance version of the Thunderbolt using a lighter airframe and an uprated engine with water injection and fan cooling. Kartveli designed an aircraft fitted with a tight-cowled Pratt & Whitney R-2800-57(C) with a war emergency rating of 2,800 hp reduced armament of six 0.50 in machine guns, a new and lighter wing, and many other changes. The only XP-47J was first flown in late November 1943. When fitted with a GE CH-5 turbo supercharger, the XP-47J achieved a top speed of 505 mph in level flight in August 1944, making it one of the fastest piston engine fighters ever built. However, by that time Republic had moved on to a new concept, the XP-72.
The P-47M was a more conservative attempt to come up with a higher-performance (“Sprint”) version of the Thunderbolt, seeking parity with the newly introduced German jet aircraft and V-1 flying bombs. In September 1944, four P-47D-27-RE airframes (s/n 42-27385 / 42-27388) were modified into prototype YP-47Ms by fitting the R-2800-57(C) engine and the GE CH-5 turbo-supercharger, a combination which could produce 2,800 hp at 32,500 ft. when using Wartime Emergency Power (water injection). Air brakes were added to the wing’s lower surfaces to allow braking after a dive onto its prey. The YP-47M had a top speed of 473 mph and it was put into limited production with 130 (sufficient for one group) built. However, the type suffered serious teething problems in the field due to the highly tuned engine. Engines were unable to reach operating temperatures and power settings and frequently failed in early flights from a variety of causes: ignition harnesses cracked at high altitudes, severing electrical connections between the magneto and distributor, and carburetor valve diaphragms also failed. Persistent oil tank ruptures in replacement engines were found to be the result of inadequate protection against salt water corrosion during transshipment. In the end, it was simply errors made by the R-2800-57(C) model engine’s manufacturers which led to these issues with the P-47M. By the time the bugs were worked out, the war in Europe was nearly over. However, P-47Ms still destroyed 15 enemy aircraft in aerial combat, normal results for any fighter type in March–May 1945 when aerial encounters with the Luftwaffe were rare. The entire production total of 130 P-47Ms were delivered to the 56th Fighter Group, and were responsible for all seven of that group’s jet shoot-downs. Twelve were lost in operational crashes with the 56th Group resulting in 11 deaths, two after VE Day, and two (44-21134 on 13 April 1945 and 44-21230 on 16 April 1945) were shot down in combat, both by ground fire.
The second YP-47M (of the batch of four converted P-47Ds) was later fitted with new wings and served as the prototype for the P-47N.
The P-47N was the last Thunderbolt variant to be produced. It was designed as an escort fighter for the Boeing B-29 Superfortress bombers flying raids on the Japanese home islands. Increased internal fuel capacity and drop tanks had done much to extend the Thunderbolt’s range during its evolution, and the only other way to expand the fuel capacity was to put fuel tanks into the wings. Thus, a new wing was designed with two 50 U.S. gal fuel tanks. The second YP-47N with this wing flew in September 1944. The redesign proved successful in extending range to about 2,000 mi (3,200 km), and the squared-off wingtips improved the roll rate. The P-47N entered mass production with the uprated R-2800-77(C) engine, with a total of 1,816 built.
The very last Thunderbolt to be built, a P-47N-25, rolled off the production line in October 1945. Thousands more had been on order, but production was halted with the end of the war in August. At the end of production, a Thunderbolt cost $83,000 in 1945 U.S. dollars. A total of 15,678 Thunderbolts of all types were built. Due to continued postwar service with U.S. military (including the Air National Guard) and foreign operators, a number of P-47s have survived to the present day, and a few are still flying.
By the end of 1942, P-47Cs were sent to England for combat operations. The initial Thunderbolt flyers, 56th Fighter Group, was sent overseas to join the 8th Air Force. As the P-47 Thunderbolt worked up to operational status, it gained a nickname: the “Jug” (because its profile was similar to that of a common milk jug of the time). Two Fighter Groups already stationing in England began introducing the Jugs 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 using P-38 Lightning.
Beginning in January 1943, Thunderbolt fighters were sent to the joint Army Air Forces – civilian Millville Airport in Millville, New Jersey in order to train civilian and military pilots.
The first P-47 combat mission took place 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. All P-47s were refitted with British radios, and missions resumed 8 April. The first P-47 air combat took place 15 April with Major Don Blakeslee of the 4th FG scoring the Thunderbolt’s first air victory (against a Focke Wulf Fw 190). On 17 August, P-47s performed their first large-scale escort missions, providing B-17 bombers with both penetration and withdrawal support of the Schweinfurt-Regensburg mission, and claiming 19 kills against three losses.
By mid-1943, the Jug was also in service with the 12th Air Force in Italy, and it was fighting against the Japanese in the Pacific with the 348th Fighter Group flying escort missions out of Brisbane, Australia. By 1944, the Thunderbolt was in combat with the USAAF in all its operational theaters, except Alaska.
Although the North American P-51 Mustang replaced the P-47 in the long-range escort role in Europe, the Thunderbolt still ended the war with 3,752 air-to-air kills claimed in over 746,000 sorties of all types, at the cost of 3,499 P-47s to all causes in combat.In Europe during the critical first three months of 1944 when the German aircraft industry and Berlin were heavily attacked, the P-47 shot down more German fighters than the P-51 (570 out of 873), and shot down approximately 900 of the 1,983 claimed during the first six months of 1944. In Europe, Thunderbolts flew more sorties (423,435) than P-51s, P-38s and P-40s combined. Indeed, it was the P-47 which broke the back of the Luftwaffe in the critical period of January–May 1944.
By the end of the war, the 56th FG was the only 8th Air Force unit still flying the P-47, by preference, instead of the P-51. The unit claimed 677.5 air victories and 311 ground kills, at the cost of 128 aircraft. Lieutenant Colonel Francis S. Gabreski scored 31 victories, including three ground kills, Captain Robert S. Johnson scored 27 (with one unconfirmed probable kill leading to some giving his tally as 28), and 56th FG Commanding Officer Colonel Hubert Zemke scored 17.75 kills.Despite being the sole remaining P-47 group in the 8th Air Force, the 56th FG remained its top-scoring group in aerial victories throughout the war.
Pictures and some info courtesy of Wikipedia.com