Variants

Over 10,000 Lightnings were manufactured in all; becoming the only U.S. combat aircraft that remained in continuous production throughout the duration of American participation in World War II. The Lightning had a major effect on other aircraft; its wing, in a scaled-up form, was used on the L-049 Constellation.

Lightning variants began with the D model. There were no Bs or Cs as the USAAF allocated the 'D' suffix to all aircraft with self-sealing fuel tanks and armor. The first combat-capable Lightning was the P-38E. The P-38E featured improved instruments, and electrical and hydraulic systems. Part-way through production, the older Hamilton Standard Hydromatic hollow steel propellers were replaced by new Curtiss Electric duraluminum propellers. The definitive armament configuration was settled upon, featuring four .50 caliber (12.7 mm) machine guns with 500 rounds per gun, and a Hispano 20 mm cannon with 150 rounds which replaced the unreliable Oldsmobile 37 mm cannon that had been tested on the P-38D.

While the machine guns had been arranged symmetrically in the nose on the P-38D, they were "staggered" in the P-38E and later versions, with the muzzles protruding from 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 led to jamming.

The first P-38E rolled out of the factory in October 1941. 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 be used in action in April 1942.

 

 

Ground crew members of the 459th Fighter Squadron, nicknamed the "Twin Dragon Squadron",

The P-38F was followed in early 1943 by the P-38G, utilizing more powerful Allisons of 1,400 hp (1,040 kW) each and equipped with a better radio. The P-38G was followed in turn by the P-38H, with further uprated Allisons (1,425 hp [1,060 kW] each), an improved 20 mm cannon and a bomb capacity of 3,200 pounds (1,450 kg). These models were also field-modified into F-4A and F-5A reconnaissance aircraft. An F-5A was modified to an experimental two-seat reconnaissance configuration, with additional cameras in the tail booms. Both the P-38G and P-38H models' performance was restricted by an intercooler system integral to the wing's leading edge that had been designed for smaller engines(Although most ground crews removed this in order to get more power at lower altitudes where the danger of oveheating was reasonably low) . The new engines could heat up too much and were subject to explosive detonation in the carburetor if operated beyond recommended limits.

Early variants did not enjoy a high reputation for maneuverability, though they could be agile at low altitudes if flown by a capable pilot, using the P-38's forgiving stall characteristics to their best advantage. From the P-38F-15 model onwards, a "combat maneuver" setting was added to the P-38's Fowler flaps. When deployed at the eight-degree maneuver setting, the flaps allowed the P-38 to out-turn many contemporary single-engined fighters at the cost of some added drag. However, early variants were hampered by high aileron control forces and a low initial rate of roll.

Lightning in maturity: P-38J, P-38L

Four P-38s flying in formation.

The definitive P-38J was introduced in August 1943. The turbocharger intercooler system on previous variants had been housed in the leading edges of the wings and had proven vulnerable to combat damage and could explode if the wrong series of controls were mistakenly activated. In the P-38J model, the streamlined engine nacelles of previous Lightnings were changed to fit the intercooler radiator between the oil coolers, forming a "chin" that visually distinguished the J model from its predecessors. While the P-38J used the same V-1710-89/91 engines as the H model, the new core-type intercooler more efficiently lowered intake manifold temperatures and permitted a substantial increase in rated power. The leading edge of the outer wing was fitted with 55-gallon fuel tanks, filling the space formerly occupied by intercooler tunnels.

The final 210 J models, designated P-38J-25-LO, alleviated the compressibility problem through the addition of a set of electrically-actuated dive recovery 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 600 miles per hour (970 km/h), although the indicated air speed was later corrected for compressibility error, and the  dive speed was lower.

The P-38J-25-LO production block also introduced hydraulically-boosted ailerons, one of the first times such a system was fitted to a fighter. This significantly improved the Lightning's rate of roll and reduced control forces for the pilot. With a truly satisfactory Lightning in place, Lockheed ramped up production, working with subcontractors across the country to produce hundreds of Lightnings each month.

There were two P-38Ks developed in 1942–1943, one official and one an internal Lockheed experiment. The first was a battered RP-38E test mule fitted with paddle-bladed "high activity" Hamilton Standard Hydromatic propellers similar to those used on the P-47. The new propellers required spinners of greater diameter, and the thrust line was slightly higher. New cowlings were fashioned to properly blend the spinners into the nacelles. The aircraft also received the chin intercoolers developed for the P-38J.

The first prototype's performance led to an official request for the second aircraft, a modified P-38G-10-LO (re-designated P-38K-1-LO) fitted with the aforementioned four-blade propellers and new Allison V-1710-75/77 (F15R/L) powerplants rated at 1,875 bhp (1,398 kW) at War Emergency Power. The AAF took delivery in September, 1943, at Eglin Field. In tests, the P-38K-1 achieved 432 mph (695 km/h) at military power and was predicted to exceed 450 mph (720 km/h) at War Emergency Power with a similar increase in load and range. The initial climb rate was 4,800 feet (1,500 m) per minute and the ceiling was 46,000 feet (14,000 m). It reached 20,000 feet (6,100 m) in five minutes flat; this with a coat of camouflage paint which added weight and drag. However, the War Production Board refused to authorize P-38K production due to the two- to three-week interruption in production necessary to implement cowling modifications for the revised spinners and higher thrust line. Some doubted Allison's ability to deliver the F15 engine in quantity.As promising as it had looked, the P-38K project came to a halt.

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, in time to support the Allied invasion of France on D-Day. Lockheed production of the Lightning 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 fitted with zero-length rocket launchers. Seven HVARs (high velocity aircraft rockets) on pylons beneath each wing, and later, ten rockets on each wing on "Christmas tree" launch racks. The P-38L also had strengthened stores pylons to allow carriage of 2,000 pound (900 kg) bombs or 300 US gallon (1,140 liter) drop tanks.

F-5B, reconnaissance version of P-38.

Lockheed modified 200 P-38J airframes 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 and drag was a minor advantage in combat.

The P-38L-5, the most common sub-variant of the P-38L, had a modified cockpit heating system which consisted of a plug-socket in the cockpit into which the pilot could plug his heat-suit wire for improved comfort. These Lightnings also received the uprated V-1710-111/113 (F30R/L) engines, and this dramatically lowered the amount of engine failure problems experienced at high altitude.

Pathfinders, Night Fighter and other variants

The Lightning was modified for other roles. In addition to the F-4 and F-5 reconnaissance variants, a number of P-38Js and P-38Ls were field-modified as formation bombing "pathfinders" or "droopsnoots", fitted with a glazed nose with a Norden bombsight, or a H2X radar "bombing through overcast" nose. A pathfinder would lead a formation of other P-38s, each overloaded with two 2,000 lb (907 kg) bombs; the entire formation releasing when the pathfinder did.

Lockheed 422 P-38M Night Lightning (44-27234 c/n 422-8238).

The additional external clutter imposed surprisingly little penalty on the P-38M's performance, and it remained faster than the purpose-built Northrop P-61 Black Widow night fighter. The Night Lightnings saw some combat duty in the Pacific towards the end of the war, but, verifiably, none engaged in combat.

One of the initial production P-38s had its turbochargers removed, with a secondary cockpit placed in one of the booms to examine how flightcrew would respond to such an "asymmetric" cockpit layout. One P-38E was fitted with an extended central nacelle to accommodate a tandem-seat cockpit with dual controls, and was later fitted with a laminar flow wing.

Proposed floatplane P-38E testbed shown with second version of upswept tail designed to keep tail out of water upon takeoff

Very early in the Pacific War, a scheme was proposed to fit Lightnings with floats to allow them to make long-range ferry flights. The floats would be removed before the aircraft went into combat. There were concerns that salt spray would corrode the tailplane, and so in March 1942, P-38E c/n 5204 was modified with a tailplane raised some 16-18 inches, booms lengthened by two feet and a rearward-facing second seat added for an observer to monitor the effectiveness of the new arrangement. A second version was crafted on the same airframe with the twin booms given greater sideplane area to augment the vertical rudders. This arrangement was removed and a final third version was fabricated that had the booms returned to normal length but the tail raised 33 inches. All three tail modifications were designed by George H. "Bert" Estabrook. The final version was used for a quick series of dive tests on December 7, 1942 in which Milo Burcham performed the test maneuvers and Kelly Johnson observed from the rear seat. Johnson concluded that the raised floatplane tail gave no advantage in solving the problem of compressibility. At no time was this P-38E testbed airframe actually fitted with floats, and the idea was quickly abandoned as the U.S. Navy proved to have enough sealift capacity to keep up with P-38 deliveries to the South Pacific.

Still another P-38E was used in 1942 to tow a Waco troop glider as a demonstration. However, there proved to be plenty of other aircraft, such as C-47s, available to tow gliders, and the Lightning was spared this duty.

Standard Lightnings were even used as crew and cargo transports in the South Pacific. They were fitted with pods attached to the underwing pylons, replacing drop tanks or bombs, that could carry a single passenger in a lying-down position, or cargo. This was a very uncomfortable way to fly. Some of the pods weren't even fitted with a window to let the passenger see out or bring in light, and one fellow who hitched a lift on a P-38 in one of these pods later said that "whoever designed the damn thing should have been forced to ride in it."

Lockheed proposed a carrier-based Model 822 version of the Lightning for the United States Navy. The Model 822 would have featured folding wings, an arresting hook, and stronger undercarriage for carrier operations. The Navy was not interested, as they regarded the Lightning as too big for carrier operations and did not like liquid-cooled engines anyway, and the Model 822 never went beyond the paper stage. However, the Navy did operate four land-based F-5Bs in North Africa, inherited from the USAAF and redesignated FO-1.

A P-38J was used in experiments with an unusual scheme for mid-air refueling, in which the fighter snagged a drop tank trailed on a cable from a bomber. The USAAF managed to make this work, but decided it was not practical. A P-38J was also fitted with experimental retractable snow ski landing gear, but this idea never reached operational service either.

After the war, a P-38L was experimentally fitted with armament of three .60 in (15.2 mm) machine guns. The .60 caliber cartridge had been developed early in the war for an infantry "anti-tank rifle", a type of weapon developed by a number of nations in the 1930s when tanks were lighter but, by 1942, the idea of taking on a tank with a large-caliber rifle was considered to be somewhere between "outdated" and "suicidal".

The cartridge was not abandoned, with the Americans designing a derivative of the German MG 151 15 mm aircraft automatic cannon around it and designating the weapon the "T17", but though 300 of these guns were built and over six million .60 caliber rounds were manufactured, they never worked out all the bugs, and the T17 never saw operational service. The cartridge was "necked up" to fit 20 mm projectiles and became a standard U.S. ammunition after the war. The T17-armed P-38L did not go beyond unsuccessful trials.

Another P-38L was modified after the war as a "super strafer," with eight .50 in (12.7 mm) machine guns in the nose and a pod under each wing with two .50 in guns, for a total of 12 machine guns. Nothing came of this conversion, either.

A P-38L was modified by Hindustan Aeronautics in India as a fast VIP transport, with a comfortable seat in the nose, leather-lined walls, accommodations for refreshments and a glazed nose to give the passenger a spectacular view.

 Noted P-38s

P-38J Lightning YIPPEE

YIPPEE

The 5,000th Lightning built, a P-38J S/N 44-23296, was painted bright vermilion red, and had the name YIPPEE painted on the underside of the wings in big white letters as well as the signatures of hundreds of factory workers. This aircraft was used by Lockheed test pilots Milo Burcham and Tony LeVier in remarkable flight demonstrations, performing such stunts as slow rolls at treetop level with one prop feathered to show that the P-38 was not the unmanageable beast of legend. Their exploits did much to reassure pilots that the Lightning might be a handful, but it was by no means a "widow maker."