World War II: Republic P-47 Thunderbolt

During the 1930s, the Seversky Aircraft Company designed several fighters for the US Army Air Corps (USAAC) under the guidance of Alexander de Seversky and Alexander Kartveli. In the late 1930s, the two designers experimented with belly-mounted turbochargers and created the AP-4 demonstrator. Having changed the company name to Republic Aircraft, Seversky and Kartveli moved forward and applied this technology to the P-43 Lancer. A somewhat disappointing aircraft, Republic continued to work with the design evolving it into the XP-44 Rocket/AP-10.

A fairly lightweight fighter, the USAAC was intrigued and moved the project forward as the XP-47 and XP-47A. A contract was awarded in November 1939, however the USAAC, watching the early months of World War II, soon concluded that the proposed fighter was inferior to current German aircraft. As a result, it issued a new set of requirements which included a minimum airspeed of 400 mph, six machine guns, pilot armor, self-sealing fuel tanks, and 315 gallons of fuel. Returning to the drawing board, Kartveli radically changed the design and created the XP-47B.

P-47D Thunderbolt Specifications

General

• Length: 36 ft. 1 in.
• Wingspan: 40 ft. 9 in.
• Height: 14 ft. 8 in.
• Wing Area: 300 sq. ft.
• Empty Weight: 10,000 lbs.
• Loaded Weight: 17,500 lbs.
• Maximum Takeoff Weight: 17,500 lbs.
• Crew: 1

Performance

• Maximum Speed: 433 mph
• Range: 800 miles (combat)
• Rate of Climb: 3,120 ft./min.
• Service Ceiling: 43,000 ft.
• Power Plant: 1 × Pratt & Whitney R-2800-59 twin-row radial engine, 2,535 hp

Armament

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• 8 × .50 in (12.7 mm) M2 Browning machine guns
• Up to 2,500 lb of bombs
• 10 x 5" unguided rockets

Development

Presented to the USAAC in June 1940, the new aircraft was a behemoth with an empty weight of 9,900 lbs. and centered on the 2,000 hp Pratt & Whitney Double Wasp XR-2800-21, the most powerful engine yet produced in the United States. In response to the aircraft's weight, Kartveli commented,"It will be a dinosaur, but it will be a dinosaur with good proportions." Featuring eight machine guns, the XP-47 featured elliptical wings and an efficient, durable turbocharger which was mounted in the fuselage behind the pilot. Impressed, the USAAC awarded a contract for the XP-47 on September 6, 1940, despite the fact that it weighed twice as much as the Supermarine Spitfire and Messerschmitt Bf 109 then being flown in Europe.

Working quickly, Republic had the XP-47 prototype ready for its maiden flight on May 6, 1941. Though it exceeded Republic's expectations and achieved a top speed of 412 mph, the aircraft underwent several teething problems including excessive control loads at high altitude, canopy jams, ignition arcing at high altitudes, less than desired maneuverability, and issues with the cloth-covered control surfaces. These issues were dealt with through the addition of a reward sliding canopy, metal control surfaces, and a pressurized ignition system. Additionally, a four-blade propeller was added to better take advantage of the engine's power. Despite the loss of the prototype in August 1942, the USAAC ordered 171 P-47Bs and 602 of the follow-on P-47C.

Improvements

Dubbed the "Thunderbolt," the P-47 entered service with the 56th Fighter Group in November 1942. Initially derided for its size by British pilots, the P-47 proved effective as a high-altitude escort and during fighter sweeps, as well as showed that it could out-dive any fighter in Europe. Conversely, it lacked the fuel capacity for long-range escort duties and the low-altitude maneuverability of its German opponents. By mid-1943, improved variants of the P-47C became available which possessed external fuel tanks to improve range and a longer fuselage for great maneuverability.

The P-47C also incorporated a turbosupercharger regulator, reinforced metal control surfaces, and a shortened radio mast. As the variant moved forward, a host of minor improvements were included such as enhancements to the electrical system and a re-balancing of the rudder and elevators. Work on the aircraft continued as the war progressed with the arrival of the P-47D. Constructed in twenty-one variants, 12,602 P-47Ds were built during the course of the war. Early models of the P-47 possessed a tall fuselage spine and a "razorback" canopy configuration. This resulted in poor rear visibility and efforts were made to fit variants of the P-47D with "bubble" canopies. This proved successful and the bubble canopy was used on some subsequent models.

Among the multitude of changes made with the P-47D and its sub-variants were the inclusion of "wet" mounts on the wings for carrying additional drop tanks as well as the use of a jettisonable canopy and a bulletproof windscreen. Beginning with the Block 22 set of P-47Ds, the original propeller was replaced with a larger type to increase performance. Additionally, with the introduction of the P-47D-40, the aircraft became capable of mounting ten high-velocity aircraft rockets under the wings and utilized the new K-14 computing gunsight.

Two other notable editions of the aircraft were the P-47M and P-47N. The former was equipped with a 2,800 hp engine and modified for use in downing V-1 "buzz bombs" and German jets. A total of 130 were built and many suffered from a variety of engine problems. The final production model of the aircraft, the P-47N was intended as an escort for B-29 Superfortresses in the Pacific. Possessing an extended range and improved engine, 1,816 were built before the end of the war.

Introduction

The P-47 first saw action with the fighter groups of the Eighth Air Force in mid-1943. Dubbed the "Jug" by its pilots, it was either loved or hated. Many American pilots likened the aircraft to flying a bathtub around the sky. Though early models possessed a poor rate of climb and lacked maneuverability, the aircraft proved extremely rugged and a stable gun platform. The aircraft scored its first kill on April 15, 1943, when Major Don Blakeslee downed a German FW-190. Due to the performance issues, many early P-47 kills were the result of tactics which utilized the aircraft's superior diving ability.

By the end of the year, the US Army Air Force was using the fighter in most theaters. The arrival of newer versions of the aircraft and a new Curtiss paddle-blade propeller greatly enhanced the P-47's capabilities, most notably its rate of climb. In addition, efforts had been made to extend its range to allow it to fulfill an escort role. Though this was ultimately taken over by the new North American P-51 Mustang, the P-47 remained an effective combatant and scored the majority of American kills in the early months of 1944.

A New Role

During this time, the discovery was made that the P-47 was a highly-effective ground-attack aircraft. This occurred as pilots sought targets of opportunity while returning from bomber escort duty. Capable of sustaining severe damage and remaining aloft, P-47s were soon fitted with bomb shackles and unguided rockets. From D-Day on June 6, 1944, through the end of the war, P-47 units destroyed 86,000 railway cars, 9,000 locomotives, 6,000 armored fighting vehicles, and 68,000 trucks. While the P-47's eight machine guns were effective against most targets, it also carried two 500-lb. bombs for dealing with heavy armor.

By the end of World War II, the 15,686 P-47s of all types had been constructed. These aircraft flew over 746,000 sorties and downed 3,752 enemy aircraft. P-47 losses during the conflict totaled 3,499 to all causes. Though production ended shortly after the war ended, the P-47 was retained by the USAAF/US Air Force until 1949. Re-designated the F-47 in 1948, the aircraft was flown by the Air National Guard until 1953. During the war, the P-47 was also flown by Britain, France, Soviet Union, Brazil, and Mexico. In the years following the war, the aircraft was operated by Italy, China, and Yugoslavia, as well as several Latin American countries who retained the type into the 1960s.

Selected Sources

• Aviation History: P-47 Thunderbolt
• Warbird Alley: P-47 Thunderbolt