The Lockheed P-38 Lightning is an American single seated, piston-engine fighter aircraft that was used during World War II.
Developed for the United States Army Air Corps, the P-38 had distinctive twin booms and a central nacelle containing the cockpit and armament.
Along with its use as a general fighter, the P-38 was utilized in various aerial combat roles including as a highly effective fighter-bomber, a night fighter, and as a long-range escort fighter when equipped with drop tanks.
The P-38 was also used as a bomber-pathfinder, guiding streams of medium and heavy bombers; or even other P-38s, equipped with bombs, to their targets.
Used in the aerial reconnaissance role, the P-38 accounted for 90 percent of the aerial film captured over Europe.
The P-38 was used most successfully in the Pacific Theatre of Operations and the China-Burma-India Theatre of Operations as the aircraft of America’s top aces, Richard Bong (40 victories), Thomas McGuire (38 victories), and Charles H. MacDonald (27 victories).
In the Southwest Pacific theatre, the P-38 was the primary long-range fighter of United States Army Air Forces until the introduction of large numbers of P-51D Mustangs toward the end of the war.
Unusual for an early-war fighter design, both engines were supplemented by turbosuperchargers
This gave the P-38 excellent high-altitude performance, making it one of the earliest Allied fighters capable of performing well at high altitudes.
The turbosuperchargers also muffled the exhaust, making the P-38’s operation relatively quiet.
The Lightning was extremely forgiving in-flight and could be mishandled in many ways, but the rate of roll in early versions was low relative to other contemporary fighters; this was addressed in later variants with the introduction of hydraulically boosted ailerons.
The P-38 was the only American fighter aircraft in large-scale production throughout American involvement in the war, from the Attack on Pearl Harbor to Victory over Japan Day.
The Lockheed Corporation designed the P-38 in response to a February 1937 specification from the United States Army Air Corps (USAAC).
Circular Proposal X-608 was a set of aircraft performance goals authored by First Lieutenants Benjamin S. Kelsey and Gordon P. Saville for a twin-engined, high-altitude “interceptor” having “the tactical mission of interception and attack of hostile aircraft at high altitude.”
Forty years later, Kelsey explained that Saville and he 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 (230 kg) of armament including ammunition, and to bypass the USAAC restriction of single-seat aircraft to one engine.
Kelsey was looking for a minimum of 1,000 lb (450 kg) of armament.
Kelsey and Saville aimed to get a more capable fighter, better at dog fighting and at high-altitude combat.
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 ever presented.
The unbuilt Vultee XP1015 was designed to the same requirement but was not advanced enough to merit further investigation.
A similar proposal for a single-engined fighter 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 turbosuperchargers and gave extra points for tricycle landing gear.
Lockheed formed a secretive engineering team to implement the project apart from the main factory; this approach later became known as Skunk Works.
The Lockheed design team, under the direction of Hall Hibbard and Clarence “Kelly” Johnson, considered a range of twin-engined configurations, including both engines in a central fuselage with push–pull propellers.
The Lockheed team chose twin booms to accommodate the tail assembly, engines, and turbosuperchargers, with a central nacelle for the pilot and armament.
The XP-38 gondola mock-up was designed to mount two .50-caliber (12.7 mm) M2 Browning machine guns with 200 rounds per gun (rpg), two .30-caliber (7.62 mm) Brownings with 500 rpg, and a United States Army Ordnance Department prototype T1 23 mm (.90 in) autocannon with a rotary magazine as a substitute for the non-existent 25 mm Hotchkiss aircraft autocannon specified by Kelsey and Saville.
In the prototype YP-38s, an Army Ordnance Department T9 37 mm (1.46 in) autocannon (later designated as the M4 in production) with 15 rounds replaced the 23 mm T1.
The 15 rounds were in three five-round clips, an unsatisfactory arrangement according to Kelsey, and the T9/M4 did not perform reliably in flight.
Further armament experiments from March to June 1941 resulted in the P-38E combat configuration of four M2 Browning machine guns, and one Hispano 20 mm (.79 in) autocannon with 150 rounds.
Clustering all the armament in the nose was unusual in U.S. aircraft, which typically used wing-mounted guns with trajectories set up to crisscross at one or more points in a convergence zone.
Nose-mounted guns did not suffer from having their useful ranges limited by pattern convergence, meaning that good pilots could shoot much farther.
A Lightning could reliably hit targets at any range up to 1,000 yd (910 m), whereas the wing guns of other fighters were optimized for a specific range.
The rate of fire was about 650 rounds per minute for the 20×110 mm cannon round (130-gram shell) at a muzzle velocity of about 2,850 ft/s (870 m/s), and for the .50-caliber machine guns (43-gram rounds), about 850 rpm at 2,900 ft/s (880 m/s) velocity.
Combined rate of fire was over 4,000 rpm with roughly every sixth projectile a 20 mm shell.
The duration of sustained firing for the 20 mm cannon was about 14 seconds, while the .50-caliber machine guns worked for 35 seconds if each magazine were fully loaded with 500 rounds, or for 21 seconds if 300 rounds were loaded to save weight for long-distance flying.
The Lockheed design incorporated tricycle undercarriage and a bubble canopy and featured two 1,000 hp (750 kW) turbosupercharged 12-cylinder Allison V-1710 engines fitted with counter-rotating propellers to eliminate the effect of engine torque, with the turbochargers positioned behind the engines, the exhaust side of the units exposed along the dorsal surfaces of the booms.
Counter-rotation was achieved by the use of “handed” engines; the crankshafts of the engines turned in opposite directions, a relatively easy task for the V-1710 modular-design aircraft powerplant.
The P-38 was the first American fighter to make extensive use of stainless steel and smooth, flush-riveted, butt-jointed aluminium skin panels.
It was also the first military airplane to fly faster than 400 mph (640 km/h) in level flight.
United States Army Air Force designation for one prototype Lockheed Model 22 first flown in 1939.
Redesigned pre-production batch with armament, 13 built.
First production variant with 0.5 in guns and a 37 mm cannon, 30 built.
Thirtieth P-38 modified with a pressurised cockpit.
Former Armée de l’air order for 667 aircraft (being reduced to 143 Lighting I’s) which was taken by the Royal Air Force.
Three delivered to RAF, remainder of the order was delivered to USAAF.
Used C-series V-1710-33 engines without turbochargers and right-hand propeller rotation
Royal Air Force designation for cancelled order of 524 aircraft using F-series V-1710 engines.
Only Lightning II built was retained by USAAF for testing, the rest of the order was completed as P-38F-13-LO, P-38F-15-LO, P-38G-13-LO, and P-38G-15-LO aircraft
22 Lightning I’s of the 143 built were retained by the USAAF for training and testing. Most were unarmed, although some retained the Lighting I armament of 2 × .50 cals and 2 x .30 cals.
121 P-322-I’s re-engined with the V-1710-27/-29 and used for training.
Most were unarmed.
Proposed variant of the P-38A, not built.
Proposed variant of the P-38A, not built.
Production variant with modified tailplane incidence, self-sealing fuel tanks, 36 built.
Production variant with revised hydraulic system, 20 mm cannon rather than the 37 mm of earlier variants, 210 built.
Proposed floatplane variant of the P-38E with upswept tail booms and fitted with droppable, fuel-filled floats.
One prototype converted from P-38E 41-1986 with modified tail booms but was not fitted with floats.
Did not enter production.
Production variant with inboard under wing racks for drop tanks or 2000 lb of bombs, 527 built.
Production variant with modified radio equipment, 1082 built.
Production variant capable of carrying 3200 lb of under wing bombs and an automatic oil radiator flap, 601 built.
Production variant with improvements to each batch, including chin radiators, flat bullet proof windscreens, power-boosted ailerons and increased fuel capacity, 2970 built.
Some modified to pathfinder configuration and to F-5C, F-5E and F-5F.
With 1425 hp engines with larger broad-bladed propellers, one built, a P-38E was also converted to the same standard as the XP-38K.
With 1600 hp engines, 3923 built which included 113 built at Vultee, later conversions to pathfinders and F-5G.
Two P-38Ls converted as tandem seated operational trainers.
Conversion of P-38L as a radar-equipped night-fighter.
Photo-reconnaissance variant of the P-38E, 99 built.
Photo-reconnaissance variant of the P-38F, 20 built.
Reconnaissance variant of the P-38G, 181 built.
Reconnaissance variant of the P-38J, 200 built, four later to the United States Navy as FO-1.
Reconnaissance variant of the P-38J, 123 conversions.
Prone-observer variant, one conversion from a F-5A.
Reconnaissance variant converted from the P-38J and P-38L, 705 converted.
Reconnaissance variant conversions of the P-38L.
Reconnaissance variant conversions of the P-38L, had a different camera configuration from the F-5F.
United States Navy designation for four F-5Bs operated for evaluation.