The Lockheed P-38 Lightning was a World War II American fighter aircraft built by Lockheed. Developed to a United States Army Air Corps requirement, the P-38 had distinctive twin booms and a single, central nacelle containing the cockpit and armament. Named "fork-tailed devil" by the Luftwaffe and "two planes, one pilot" by the Japanese, this unique aircraft was used in a number of different roles including dive bombing, level bombing, ground strafing, photo reconnaissance missions, and extensively as a long-range escort fighter when equipped with drop tanks under its wings.
The P-38 was used most successfully in the Pacific Theater of Operations and the China-Burma-India Theater of Operations as the mount of America's top aces, Richard Bong (40 victories) and Thomas McGuire (38 victories). In the South West Pacific theater, the P-38 was the primary long-range fighter of United States Army Air Forces until the appearance of large numbers of P-51D Mustangs toward the end of the war. The P-38 was probably the quietest fighter in history, the exhaust merely whispering out of the turbo exits. It was extremely forgiving, and could be mishandled in many ways, but the rate of roll was too slow for it to excel as a dogfighter. The P-38 was the only American fighter aircraft in active production throughout the duration of American involvement in the war, from Pearl Harbor to VJ Day.
Design and development
Lockheed designed the P-38 in response to a February 1937 specification from the United States Army Air Corps. Circular Proposal X-608 was a set of aircraft performance goals authored by First Lieutenant Benjamin S. Kelsey (later Brigadier General) and First Lieutenant Gordon P. Saville (later General) for a twin-engine, high-altitude interceptor aircraft having "the tactical mission of interception and attack of hostile aircraft at high altitude." Kelsey recalled in 1977 that he and Saville drew up the specification using the word "interceptor" as a way to bypass the inflexible Army Air Corps requirement for pursuit aircraft to carry no more than 500 lb (227 kg) of armament including ammunition, as well as the restriction of single-seat aircraft to one engine. Kelsey was looking for a minimum of 1,000 lb (454 kg) of armament. Specifications called for a maximum airspeed of at least 360 mph (580 km/h) at altitude, and a climb to 20,000 ft (6,100 m) within six minutes; the toughest set of specifications USAAC had presented to that date. The unbuilt Vultee XP1015 was designed to the same requirement, but was not advanced enough to merit further investigation. A similar single-engine proposal was issued at the same time: Circular Proposal X-609, in response to which the Bell P-39 Airacobra was designed. Both proposals required liquid-cooled Allison V-1710 engines with turbo superchargers and tricycle landing gear.
The Lockheed design team, under the direction of Hall Hibbard and Clarence "Kelly" Johnson, considered a range of twin-engine configurations including both engines in a central fuselage with push-pull propellers.
The eventual configuration was rare in terms of contemporary fighter aircraft design, with only the Fokker G.1 and later Northrop P-61 Black Widow having a similar planform. The Lockheed team chose twin booms to accommodate the tail assembly, engines, and turbo superchargers, with a central nacelle for the pilot and armament. The nose was designed to carry two .50 in (12.7 mm) M2 Browning machine guns, with 200 rpm, two .30 in (7.62 mm) Brownings, with 500 rpm, and an Oldsmobile 37 mm (1.46 in) cannon with 15 rounds. Clustering all the armament in the nose was unlike most other U.S. aircraft which used wing-mounted guns with trajectories set up to crisscross at one or more points in a "convergence zone." Guns mounted in the nose did not suffer from having their useful ranges limited by pattern convergence, meaning good pilots could shoot much farther. A Lightning could reliably hit targets at any range up to 1,000 yd (910 m), whereas other fighters had to pick a single convergence range between 100 and 250 yd (230 m). The clustered weapons had a "buzz saw" effect on any target at the receiving end, making the aircraft effective for strafing as well.
The Lockheed design incorporated tricycle undercarriage and a bubble canopy, and featured two 1,000 hp (746 kW) turbo-supercharged 12-cylinder Allison V-1710 engines fitted with counter-rotating propellers to eliminate the effect of engine torque, with the superchargers positioned behind the engines in the booms. It was the first American fighter to make extensive use of stainless steel and smooth, flush-riveted butt-jointed aluminum skin panels. It was also the first fighter to fly faster than 400 mph (640 km/h).
Lockheed won the competition on 23 June 1937 with its Model 22 and was contracted to build a prototype XP-38 for US$163,000, though Lockheed's own costs on the prototype would add up to US$761,000. Construction began in July 1938 and the XP-38 first flew on 27 January 1939 at the hands of Ben Kelsey. Kelsey proposed a speed dash to Wright Field on 11 February 1939 to relocate the aircraft for further testing. General Henry "Hap" Arnold, commander of the USAAC, approved of the record attempt, and recommended a cross-country flight to New York. The flight set a speed record by flying from California to New York in seven hours and two minutes, but was downed by carburetor icing short of the Mitchel Field runway in Hempstead, New York, and was wrecked. However, on the basis of the record flight, the Air Corps ordered 13 YP-38s on 27 April 1939 for US$134,284 apiece. (The initial "Y" in "YP" was the USAAC's designation for a "prototype" while the "X" in "XP" was for "experimental".) Lockheed's Chief test pilot Tony LeVier angrily characterized the accident as an unnecessary publicity stunt. According to Kelsey, the loss of the prototype, instead of hampering the program, speeded the process by cutting short the initial test series. The success of the aircraft design contributed to Kelsey's promotion to captain in May, 1937.
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Manufacture of the YP-38s fell behind schedule, at least partly due to the need for mass-production suitability making them substantially different in construction than the prototype. Another factor was the sudden required facility expansion of Lockheed in Burbank, taking it from a specialized civilian firm dealing with small orders to a large government defense contractor making Venturas, Harpoons, Lodestars, Hudsons, and designing the Constellation airliner for TWA. The first YP-38 was not completed until September 1940, with its maiden flight on 17 September.[23] The 13th and final YP-38 was delivered to the Air Corps in June 1941; 12 aircraft were retained for flight testing and one for destructive stress testing. The YPs were substantially redesigned and differed greatly in detail from the hand-built XP-38. They were lighter, included changes in engine fit, and the propeller rotation was reversed, with the blades rotating outwards (away) from the cockpit at the top of their arc rather than inwards as before. This improved the aircraft's stability as a gunnery platform.
