Lockheed P-38 Lightning P-38J

The P-38J grew out of a problem inherited from the P-38G and P-38H: the turbosupercharger intercooler sat in the wing leading edge, a system designed for the YP-38's less powerful engines. With the Allisons pushed harder, charge air temperature rose above the limits recommended by the engine maker, and detonation set in if high power was held for long periods; the ducting was also vulnerable to combat damage and could burst if the pilot activated the wrong sequence of controls. Lockheed set aside a dozen aircraft from the P-38G programme as prototypes for the new version and tested the installation on a two-seat RP-38E test mule. Subcontractors were initially unable to supply enough of the new intercoolers and radiators for both Burbank lines, and the War Production Board refused to slow production: one line built the P-38H as a stop-gap while the other began the P-38J in August 1943.

The fix was a redesigned nacelle. The new core-type intercooler radiator was fitted between the oil coolers under each engine, forming the chin that visually sets the J apart from its predecessors. The engines were the same V-1710-89/91 as the P-38H - the English Wikipedia credits them with 1,425 hp (1,063 kW) - but the new intercooler cooled the manifold air far more efficiently and allowed a substantial increase in rated power. The space vacated by the old ducting in the outer-wing leading edge was filled with 55 US gal (210 L) fuel tanks on each side; parts shortages kept them out of the early blocks. The Italian Wikipedia, which gives the company designation Model 422-81-14, sums up the block-by-block evolution: the J-5 increased fuel, the J-10 added a flat bullet-proof windscreen and the J-25 brought servo-assisted ailerons and dive brakes. The German edition condenses the variant into three features: intercooler moved under the engine next to the oil cooler, an additional wing tank and a dive brake.

Those flaps answered compressibility, the flaw that had made the P-38 feared in dives. Lockheed test pilots tried them in February 1943: mounted under the wing outboard of the nacelles, they extended 35 degrees in 1.5 seconds; rather than braking the aircraft, they altered the pressure distribution so the wing kept its lift. Their arrival was troubled. In March 1944 an RAF fighter mistook for a German Focke-Wulf Condor the Douglas C-54 carrying to England some 200 kits meant for the P-38J-10s and J-20s already in Europe, and shot it down. At Burbank, P-38Js coming off the line in spring 1944 were modified in the open air on the ramp, and the flaps entered the assembly line only in June 1944, on the final 210 aircraft, the P-38J-25-LO; the French Wikipedia dates their introduction to April 1944 instead. The same block introduced hydraulically boosted ailerons, among the first fitted to a fighter, which greatly improved the rate of roll and lightened the controls. The J-25 and the P-38L that followed are regarded as the definitive Lightnings. With these improvements a USAAF pilot reported diving at almost 600 mph (970 km/h), although the figure was later corrected downward for the airspeed indicator's compressibility error.

In Europe the P-38J reached an Eighth Air Force that needed long-range escorts for its heavy bombers and had suffered high-altitude and cold-weather engine trouble with the G and H. The J remedied many of those failings, but it came late. Lockheed test pilot Tony LeVier spent four months touring the bases in a Lightning named Snafuperman, brought up to J-25 standard at the company's modification centre near Belfast, and in March 1944 routinely flew manoeuvres the Eighth considered suicidal; by then the decision to re-equip with Mustangs had already been taken, and by September 1944 all but one of the Eighth's Lightning groups had converted to the P-51. Flying from Italy, by contrast, the J and L had great success over Germany at all altitudes. On 10 June 1944, 96 P-38Js of the 1st and 82nd Fighter Groups took off from Italy for a dive-bombing attack on Ploiești: 46 aircraft of the 82nd each carried one 1,000-pound bomb, released at or below about 3,000 feet, on a route of some 1,255 miles (2,020 km). Seven Lightnings fell to flak over the target; the 71st Fighter Squadron fought Romanian IAR 81C fighters below 300 feet in a narrow valley and lost nine aircraft. The USAAF lost 22 aircraft and claimed 23 victories; the profile was not repeated, but the 82nd received the Presidential Unit Citation.

In the Pacific, the Spanish Wikipedia holds that the slow roll response exploited by Zero pilots was not cured until late 1943, with the arrival of the P-38J. The best-documented example is P-38J-15-LO 42-103993, the fifteenth J-15 built. According to Pacific Wrecks, it first flew at Burbank on 28 December 1943 with Lockheed test pilot Earl C. Crawford, was delivered on the 31st and on 4 January 1944 went through the Dallas Modification Center to receive its leading-edge tanks; on 15 January it was shipped from Oakland to Australia. In February it was assigned to Captain Richard I. Bong of the Fifth Air Force's V Fighter Command at the start of his second tour. Bong named it “Marge”, with her photo on the nose, and had the nose cone, spinners, wingtips and tail tips painted red simply because he liked the colour; the scoreboard already showed 25 flags. That month he flew fifteen combat missions in a P-38J-15, probably all in this aircraft, and on 15 February, escorting A-20s over Kavieng alongside Lieutenant Colonel Thomas J. Lynch, he shot down a Ki-61 for his twenty-second victory. On 24 March 1944, flown by 2nd Lt. Thomas E. Malone of the 421st Night Fighter Squadron, it suffered an engine failure and crashed in New Guinea; Malone bailed out and survived, and in May 2024 the Richard I. Bong Veterans Historical Center and Pacific Wrecks announced they had found wreckage bearing its serial number. Bong ended the war with 40 victories, all in P-38s, and Thomas McGuire of the 475th Fighter Group with 38; the sources consulted do not specify the version of each of their aircraft.

The P-38J also had a life away from combat. The 5,000th Lightning, P-38J-20-LO 44-23296, was painted vermilion red with YIPPEE under the wings and the signatures of hundreds of factory workers, and was flown in demonstrations by Lockheed pilots including Milo Burcham, Jimmie Mattern and Tony LeVier. P-38Js were used to test a mid-air refuelling scheme that snagged a drop tank trailed by a bomber and a retractable ski undercarriage, neither of which entered service. The variant produced the 200 F-5B reconnaissance aircraft, the F-5C and F-5E conversions and the droop-snoot formation leaders with a Norden bombsight or H2X radar. The Republic of China received 15 P-38Js and P-38Ls. After the war LeVier bought a P-38J and painted it red for racing and air shows, and from June 1948 the survivors were redesignated ZF-38J.