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The P-38H was the standard version of the Lightning during the second half of 1943. In some respects it was an intermediate design. It saw a change of engine, to the Allison V-1710-89/91, which could provide a potential maximum horsepower of 1,425 each. However, the intercoolers on the P-38H were still carried on the leading edge of the wings, between the engine nacelles and the pilot pod, and did not provide enough of a cooling effect to allow the new engines to be run at full power. Instead it was restricted to 1,240 hp, a total loss of 370 hp (and 160 hp less than in the P-38G). Despite this, the P-38H is still reported as being 2 mph faster than the P-38G.
This slight improvement in performance probably came from the more sophisticated automation that came with the new engines, which featured automatic controls for the oil, coolant shutters and turbo-superchargers.
The P-38H saw a change of cannon from the original M1 to the AN/M2C.
A total of 601 P-38Hs were built, in two production blocks (226 H-1s and 375 H-5s).
According to an 8th Air Force report on tactical developments between 1942 and 1945 in November 1943 the P-38 could escort bombers to targets up to 520 miles from their base. At this point they were equipped with two 75 gallon fuel tanks. In February 1944 larger 108 gallon drop tanks became available, extending the P-38’s radius of action to 585 miles, giving it the range to escort bombers all the way to Berlin.
This effective range casts an interesting light on the maximum range figures quoted for the P-38H, of around 2,400 miles. To achieve this range, the aircraft had to be equipped with two 300 gallon drop tanks, but these could only be used for ferrying purposes. These tanks allowed the P-38 to carry 900 gallons of fuel. The smaller 75 gallon tanks reduced that capacity to 450 gallons, or a ferrying range of 1,200 miles, apparently enough to reach Berlin, and 160 miles further than the 520 mile radius given by the 8th Army. However, escort fighters had to keep pace with their bombers – the B-17 had an economical cruising speed of under 200 mph – forcing the P-38s to travel below their most efficient cruising speed or to weave around the bombers, travelling significantly longer distances than the aircraft they were protecting. On the rare occasions that fighter squadrons were sent on intruder missions they were able to reach much further into Germany.
Stats
Engine: Allison V-1710-89/-91 (F-17)
Horsepower: 1,425, limited to 1,240 in P-38
Maximum Speed: 402 mph at 25,000 feet
Cruising Speed: 250 mph
Rate of climb: 6.5 minutes at 20,000 feet
Ceiling: 40,000 feet
Armament: Four .50in machine guns, one 20mm cannon