Lockheed P-38 Lightning
Photo by Evert J. van Koningsveld.
Unusual twin-boom WWII fighter probably inspired by the Fokker G.I
aircraft. Most US fighters with the Allison V-1710 engine suffered from bad performance at higher altitudes,
but the P-38 Lightning was fitted with turbochargers in the tail booms, behind the engines. Armament was concentrated
in the nose of the central nacelle. The P-38 was not very suitable for combat in Europe, but achieved
great succes in the Pacific. The P-38F was the first combat-ready model. The P-38J introduced new air
intakes for the radiators, finally solving cooling problems. 10037 built.
Engines: 2 * 900 kW Allison V-1710-49/53
Wing Span: 15.85m
Wing Area: 30.5 m2
Empty Weight: 5902 kg
Max.Weight: 7173 kg
Max. Speed: 628 km/h
Max. Range: 1125 km
Armament: 1*g20mm 4*mg 12.7mm
Engines: 2 * Allison V-1710-89/91
Wing Span: 15.85m
Wing Area: 30.5 m2
Empty Weight: 6401 kg
Max.Weight: 9806 kg
Speed: 666 km/h
Range: 3025 km
Armament: 1*g20mm 4*mg 12.7mm 2*b726 kg
Engines: 2 * Allison V-1710-111/113 liquid-cooled turbo supercharged V-12, 1,600 hp (1,194 kW) each
Wing Span: 15.85m
Wing Area: 30.43 m2
Wing loading: 260.9 kg/m²
Wing Aspect ratio: 8.26
Empty Weight: 5800 kg
Max.Weight: 9798 kg
Speed: 667 km/h
Stall speed: 170 km/h
Range (ferry): 3640 km
Ceiling: 13,400 m
Armament: 1 * Hispano 20mm cannon with 150 rounds, 4 Colt-Browning MG53-2 0.50 (12.7mm) machine guns with 500 rounds per gun, 2*b726 kg
The Lockheed P-38 Lightning was one of the most important American fighters of the Second World War. Although its operational record was somewhat mixed, in general the P-38 was a fast, powerful and capable aircraft that performed well in a wide range of roles.
The aircraft had twin booms with the engines mounted forward, and a single, central nacelle containing the pilot and armament. The engine sounds were a unique, rather quiet "whuffle," because the exhausts were muffled by the turbochargers of the twin Allison V12s. The canopy could not be opened without severe buffeting, so pilots were often too hot in the tropics. In northern Europe, the distance of the engines from the cockpit prevented effective heating of the cockpit. Thus it was always either too hot or too cold. However, late variants of the P-38 received modifications that removed this problem, giving the pilot full control of the powerful aircraft.
Lockheed designed the P-38 in response to a 1937 United States Army Air Corps (USAAC) request for a high-altitude interceptor, capable of 360 mph at altitude of 20,000 ft, (580 km/h at 6100 m). The Bell P-39 Airacobra and the Curtiss P-40 Warhawk were designed to meet the same request.
At that time, US piston engines could not push fighter performance to ideal limits so the Lockheed design team, under the direction of Clarence "Kelly" Johnson decided to use two turbo-supercharged 12 cylinder Allison V-1710 engines which had not been rated at even 1000 hp (746 kW). The P-38 was the first plane developed by the new Skunk works team in Burbank, California.
Johnson's concepts covered a range of configurations, but the Lockheed team chose twin booms, seen earlier on the Fokker G.I, to accommodate the empennage and the engines, and the central nacelle for the pilot and armament. The propellers rotated in opposite directions to eliminate the effect of torque. The superchargers were positioned in the booms, behind the engines. Armament comprised four machine guns in the nose of the nacelle clustered around a cannon. The design featured tricycle undercarriage, and was the first fighter to use it.
The prototype Lockheed Model 22, later designated XP-38, rolled out in December 1938 and first flew on January 27, 1939. It set a cross-continent speed record by flying from California to New York on February 11, 1939 in 7 hours and 2 minutes, including two fuel stops. Unfortunately, the prototype landed short of the runway in New York and was wrecked, much to the distress of the Lockheed engineering team. They had opposed the flight, but it was done at the insistence of General Henry "Hap" Arnold, commander of the USAAC, as a publicity stunt.
Although the loss of the aircraft was a serious setback (putting the program back two years), on the basis of the record flight the Air Corps ordered 13 YP-38s in April 1939. If the XP-38 had not been destroyed, orders would not have been placed until the prototype had been thoroughly evaluated.
However, manufacture of the YP-38s proved troublesome, and the first didn't roll off the production line until September 1940, with the last delivered in June 1941. Although they looked much like the hand-built XP-38, they were substantially redesigned and differed greatly in detail. They were lighter, and there were changes in engine fit, particularly in that propeller spin rotation was reversed, with the blades rotating outwards (away) from the cockpit at the top of their arc rather than inwards as before. This change, according to Kelly Johnson, improved the aircraft's stability as a gunnery platform.
Although weapons were not fitted in most of these aircraft, they were designed to be armed with two Browning .50 calibre (12.7 mm) machine guns with 200 rounds per gun, two .30 calibre (7.62 mm) Brownings with 500 rounds per gun, and an Oldsmobile 37 mm cannon with 15 rounds.
Orders were already in hand from France, Britain, and the USAAC. The French and the British ordered a total of 667, with a Model 322F for the French and a Model 322B for the British. Each variant had unique modifications for their respective air arms, such as metric measurements on the flight indicators for the French aircraft, but they both shared a major change from all other P-38 variants in that turbo-superchargers were deleted and the left-handed and right-handed engine arrangement was changed to twin right-handed engines.
As turbo-superchargers were a new technology, the Anglo-French purchasing commission was concerned that turbo-superchargers might lead to delays, and being intended for medium-altitude combat, were not needed. The requirement for sole use of right-handed engines was for commonality with the large numbers of Curtiss Tomahawks both nations had on order. (Moreover, the turbocharged engines were prohibited from export by the U.S. government.) Lockheed engineers protested strongly against this decision, and privately labeled the variant the "castrated" P-38.
After the fall of France in June 1940, the British took over the entire order. They decided that only the first 143 of the order would be delivered in the unsupercharged format, as Model 322 Lightning Is, with the remaining 524 to be delivered with turbo-superchargers and left and right-handed engines, as Model 322 Lightning IIs.
The British never got that far. Three of the unsupercharged Lightning Is were delivered to the UK in March 1942, and were promptly given a thumbs-down. They "topped out" at 480 km/h (300 mph) and had nasty handling characteristics, so the entire order was cancelled.
The remaining 140 Lightning Is were completed for the USAAF. The rest of this batch, most refitted with contra-rotating engines but still minus turbo-superchargers, were relegated to United States Army Air Force (USAAF, as the designation USAAC had been changed in the interim) for training under the designation RP-322.
These aircraft helped the USAAF train new pilots to fly a powerful and complex new fighter. The RP-322 was actually a fairly hot aircraft at low altitude, and perfectly satisfactory in the training role. The other positive result of this fiasco was to give the aircraft the name "Lightning". Lockheed's tradition of naming their planes after mythological and celestial figures originally dubbed her Atalanta, but the RAF name won out.
Thirty initial production P-38 Lightnings were delivered to the USAAF in mid-1941. Although not all these aircraft were armed, when they were, they were fitted with four .50 calibre (12.7 mm) machine guns (instead of the two .50 calibre (12.7 mm) and two .30 calibre (7.62 mm) weapons of their predecessors) but the 37 mm cannon was retained. They also had armor glass, cockpit armor, and fluorescent cockpit controls. One was completed with a pressurized cabin on an experimental basis and designated XP-38A.
These 30 aircraft were part of an order for 66, but in light of USAAF feedback, the remaining 36 in the batch were fitted with various small improvements such as self-sealing tanks and enhanced armor protection to make them combat capable. For some odd reason, the USAAF specified that these 36 aircraft were to be designated P-38D. As a result, there never were any P-38Bs or P-38Cs. Early production variants of the Lightning are a confusing subject. None of these aircraft ever saw combat. Their main role in the story of the P-38 was to work out bugs and give the USAAF experience with handling the type.
Tail flutter was quickly found to be a problem. In an attempt to fix it, mass balances were attached to little booms in the middle of the elevator. This fix was derided by Kelly Johnson, who regarded the weights as useless, and in fact the buffeting eventually proved to be due to the straight connection of the wing root to the fuselage pod. A few aerodynamic changes, most particularly the addition of a wing-root fillet, solved the problem. Nonetheless, the external balances were a feature of every P-38 built from then on.
A more serious problem was "compressibility stall," the tendency of the controls to simply lock up in a high-speed dive, leaving the pilot no option but to bail out. The tail structure also had a nasty tendency to fall apart under such circumstances, and in fact this problem killed a YP-38 test pilot, Ralph Virden, in November 1940.
A USAAC major named Signa Gilkey managed to stay with a YP-38 in a compressibility lockup, riding it out until he got to denser air, where he recovered using elevator trim. This feat led to experiments that would eventually resolve the problem.
Kelly Johnson later recalled: "I broke an ulcer over compressibility on the P-38 because we flew into a speed range where no one had ever been before, and we had difficulty convincing people that it wasn't the funny-looking airplane itself, but a fundamental physical problem. We found out what happened when the Lightning shed its tail, and we worked during the whole war to get 15 more knots [28 km/h] more speed out of the P-38. We saw compressibility as a brick wall for a long time. Then we learned how to get through it."
That would not be until later, however, and the new P-38 had other defects. The most dangerous problem was that both engines were "critical" engines losing one on takeoff, which happened often, created "critical torque," rolling the plane towards the live engine's wingtip, rather than the dead engine's. Normal reflex in pilots flying twin engine aircraft would be to push the remaining engine to full throttle when they lost an engine on takeoff, but in the P-38, the resulting critical torque would produce such an uncontrollable level of asymmetric roll that the aircraft would flip over and slam upside-down into the ground. Eventually, procedures were devised to allow a pilot to deal with the situation by reducing power on the running engine, feathering the prop on the dead engine, and then increasing power gradually until the aircraft was in stable flight.
The P-38E, the first combat-capable Lightning
The first combat-capable Lightning was the P-38E, which featured improved instruments, electrical systems, and hydraulic systems; new Curtiss Electric duraluminum propellers (though early P-38E production retained the older Hamilton Standard Hydromatic hollow steel propellers) and the definitive armament configuration, featuring four 12.7 mm machine guns with 500 rounds per gun and a Hispano 20 mm cannon with 150 rounds instead of the unreliable Oldsmobile 37 mm gun.
Interestingly, while the machine guns had been arranged symmetrically in the nose on earlier variants, they were "staggered" in the P-38E and later versions, with the muzzles sticking out of the nose in the relative lengths of roughly 1:4:6:2. This was done to ensure a straight ammunition belt feed into the weapons, as the earlier arrangement had led to jamming.
The first P-38E rolled out of the factory in October 1941. 210 P-38Es were built. They were followed, starting in April 1942, by the P-38F, which incorporated racks inboard of the engines for fuel tanks or a total of 900 kg (2,000 pounds) of bombs. 527 P-38Fs were built. Over a hundred P-38Es were completed in the factory or converted in the field to a photo-reconnaissance variant, the F-4, in which the guns were replaced by four cameras. Most of these early reconnaissance Lightnings were retained stateside for training, but the F-4 was the first Lightning to see combat, beginning operations out of Australia and then New Guinea in April 1942. Three of the F-4s were operated by the Royal Australian Air Force in this theater for a short period beginning in September 1942.
By June 1942, P-38s were operating in the Aleutians as well. The fighter's long range made it well-suited to the campaign over the almost 2,000 km (1,200 mile) long island chain, and it would be flown there for the rest of the war. It was one of the most rugged environments available for testing the new aircraft under combat conditions. More Lightnings were lost due to weather and other conditions than enemy action. There were cases where Lightning pilots, mesmerized by flying for hours over gray seas under gray skies, simply flew into the water. Nonetheless, the P-38 scored successes. On 4 August 1942, two P-38Es, operating at the 1,600 km (1,000 mile) end of a long-range patrol, bounced a pair of Japanese Kawanishi H6K "Mavis" flying boats and destroyed them. They were the first of many Japanese aircraft to be shot down by the Lightning.
In the meantime, Lightnings of the 1st Fighter Group were being flown across the Atlantic via Iceland to England, though most of them made the trip on freighters. On 15 August, a P-38F and a P-40 operating out of Iceland shot down a Focke-Wulf Fw 200 Condor shipping raider over the Atlantic. This was reputedly the first Luftwaffe aircraft destroyed by the USAAF.
The Lightnings sent to England were part of the force being built up for the invasion of North Africa. The invasion took place in November 1942, and Lightning units, including a photo-reconnaissance unit under command of Colonel Elliott Roosevelt, the American president's son, then began acquiring familiarity with operating under "austere conditions" and matching their skills and aircraft against the enemy.
The Lightning proved surprisingly maneuverable at low altitudes, mostly due to very docile low-speed stall characteristics. The contra-rotating props had the benefit of eliminating the effects of engine torque, and on occasion a Lightning could even out-turn smaller fighters. However, maneuverability was not its strong suit, its major virtue in combat being a "terrific zoom climb" that would leave pursuers in the dust. Luftwaffe pilots also quickly learned not to make head-on attacks on the P-38, since its concentrated firepower ensured mutual destruction. Although not the best dogfighter, the P-38 was a formidable interceptor and attack aircraft and in the hands of a good pilot could be dangerous in air-to-air combat. The P-38 remained a force in the Mediterranean for the rest of the war.
A growing need for long-range escort fighters in Northwest Europe to protect heavy bomber operations resulted in four groups of Lightnings being deployed to the 8th Air Force in 1943-44. Although the P-38 gained a reputation with the Luftwaffe as the "fork-tailed devil," its performance at frigid high altitudes was disappointing and it proved difficult to maintain. By September 1944, all the Lightning groups in the 8th Air Force had converted to the P-51 Mustang.
However, the Lightning proved ideally suited for the Pacific theater, as it combined excellent performance with very long range. While the P-38 could not out-maneuver the Zero and most other Japanese fighters, its speed and climb gave American pilots the option of choosing to fight or run and its focused firepower was even more deadly to lightly-armored Japanese warplanes than to the Germans. Jiro Horikoshi, designer of the Zero, wrote: "The peculiar sound of the P-38's twin engines became both familiar and hated by the Japanese all across the South Pacific."
The P-38F was followed in early 1943 by the P-38G, with more powerful Allisons with 1,400 hp (1,040 kW) each and a better radio. 1,082 P-38Gs were built. The P-38G was followed in turn by 601 similar P-38Hs, with a further uprated Allisons with 1,425 hp (1,060 kW) each, an improved 20 mm cannon, and a bomb capacity of 1,450 kg (3,200 pounds). These models were also field-modified into F-4B and F-5A reconnaissance aircraft.
The Lightning P-38J, P-38L
The definitive P-38J was introduced in August 1943. The twin booms of previous Lightnings featured a sleek, art-deco streamlining. However, the turbocharger intercooler system that had been housed in the leading edges of the wings had proven vulnerable to combat damage and could explode if the wrong series of controls were mistakenly activated. Ultimately, they were inefficient, subsequently, engine fit was rethought.
The most noticeable feature of the new fit was that the intercooler radiators were placed under the prop hub at the front of the booms, forming a "chin" that made the P-38J visibly different from its predecessors. The space left open in the wings was replaced with fuel tanks, further increasing the aircraft's long range. The revised radiator configuration made cooling much more efficient and improved both performance and reliability.
Late production P-38Js also finally ameliorated the compressibility problem through the introduction of minor aerodynamic changes, particularly the addition of a set of small dive flaps just outboard of the engines on the bottom centerline of the wings. With these improvements, a USAAF pilot reported a dive speed of almost 970 km/h (600 mph) and recovered in one piece. After the Second World War, it was realized that the reported air speed had to be corrected for compressibility error as well, so the actual dive speed was lower than reported.
Finally, later production of the P-38J was equipped with power-boosted flight controls, one of the first times such a system was fitted to a fighter, and did much to improve the Lightning's roll rate at high speeds and maneuverability. With a truly satisfactory Lightning in place, Lockheed ramped up production, working with subcontractors across the country to produce hundreds of Lightnings each month. Some 2,970 P-38Js were built.
There were two P-38Ks developed in 1942-1943. The first was a modified P-38E with the Hamilton Standard propellers being fitted to the P-47 and the new intercoolers being developed for the P-38J, its performance led to the development on the second aircraft. A modified P-38G (re-designated P-38K-1-LO) was fitted with the propellers and a new Allison engine with 100 more bhp than even the later P-38L. In tests it was rated at 432 mph in Military Power and predicted to exceed 450 mph in War Emergency Power with a similar increase in rate of climb, load, ceiling and range. However, the War board refused the change due to the two to three-week shutdown of the Lightning production line needed to redesign the cowlings to accomodate the new engine.
The P-38L was the most numerous variant of the Lightning, with 3,923 built, 113 by Consolidated-Vultee in their Nashville plant. It entered service with the USAAF in June of 1944, just in time for close support of Allied troops who invaded occupied France on D-Day. Lockheed production of the Lighting was distinguished by a suffix consisting of a production block number followed by "LO," for example "P-38L-1-LO," while Consolidated-Vultee production was distinguished by a block number followed by "VN," for example "P-38L-5-VN."
The P-38L was the first Lightning to offer zero-length rocket launchers, at first, with seven HVARs (high velocity aircraft rockets) on pylons beneath each wing but later with ten rockets on each wing on "Christmas tree" launch racks. The P-38L also had strengthened stores pylons to allow carriage of 900 kg (2,000 pound) bombs or 1,140 liter (300 US gallon) drop tanks.
200 P-38J airframes were modified in production to become unarmed F-5B photo-reconnaissance aircraft, while hundreds of other P-38Js and P-38Ls were field-modified to become F-5Es, F-5Fs, and F-5Gs. A few P-38Ls were field-modified to become two-seat TP-38L familiarization trainers.
Late model Lightnings were delivered unpainted, as per USAAF policy established in 1944. At first, field units tried to paint them, since pilots worried about being too visible to the enemy, but it turned out the reduction in weight was a minor plus in combat.
15 P-38Js and P-38Ls were flown by the Nationalist Chinese late in the war, and, after the war, they also received a similar number of F-5Es and F-5Gs.
The new P-38 Lightning was operated by the US Army Eighth Air Force in Europe beginning in 1943 for long-range escort missions, but did not achieve great success in this role. This was partly because it was harder to fly than a single-engine aircraft and, since it had no engine in front of the pilot to keep him warm, it was an "ice-box" on high-altitude missions. Still, the main reason for the P-38's relative failure in high-altitude operations in the European Theatre was due to engine failures experienced above 20,000 feet. The reasons for frequent engine failures were due to failing spark plugs and other parts that could not use the European, rain-drenched fuel.
The P-38L-5 - the most common sub-variant of the P-38L - had a modified cockpit heating system which consisted of a plug in the cockpit in which the pilot would plug his heat suit wire, giving him more comfort. As well, P-38L's were fitted with hydraulically operated dive flaps and ailerons, giving them better handling at higher speeds. These Lightnings also received the uprated V-1710-111/113 (F30) engines, and this dramatically lowered the amount of engine failure problems experienced at high altitude. By this time, however, the earlier P-38 models had left a negative reputation in the minds of those in charge of fighter escort for USAAF bombers and had been replaced by the more fuel-efficient, agile and cheaper-to-produce P-51 Mustang.
The Eighth operated F-5 recon variants with more enthusiasm and success. They were also operated by a Free French squadron, which worked as part of the USAAF Twelfth Air Force; the French would continue to operate the type up to 1952.
Unfortunately, since F-5s operated alone, when their missions went wrong, they generally disappeared without a trace. The noted aviation pioneer and writer Antoine de Saint-Exupery vanished in an F-5 while on a reconnaissance mission over Lyon, France, on 31 July 1944. recently, a French scuba diver found the wreckage of a Lightning in the Mediterranean off the coast of Marseille in 2000, and it was confirmed in April 2004 as Saint-Exupery's.
The RAF's legendary photo-recon.. "ace," Wing Commander Adrian Warburton DSO DFC, was the pilot of a Lockheed F-5B borrowed from the USAAF that took off on 12 April 1944 to photograph targets in Germany. W/C Warburton failed to arrive at the rendezvous point and was never seen again. (In 2003, remains uncovered in Germany from a wrecked USAAF F-5B Lightning were found to be his aircraft.)
Despite its mixed career in Europe, the Lightning remained an outstanding success in the Pacific. Freezing cockpits were not a problem in the warm tropics. In fact, since there was no way to open a window while in flight, as it caused buffeting by setting up turbulence through the tailplane, it was often too hot, and pilots would fly stripped down to shorts, tennis shoes, and parachute.
The P-38 fought all around the Pacific, from the Aleutians to New Guinea to Burma and China. A P-38 piloted by Clay Tice was the first American aircraft to land in Japan after VJ-Day, when he and his wingman set down on Nitagahara because his wingman was low on fuel.