Lockheed P-38 Lightning Design Info

Video from the channel Greg's Airplanes and Automobiles about Lockheed P-38 Lightning, linked on its Above Ten Thousand entry. Duration: 41:34. Language: English. Video type: Documentary.

Explanatory piece on the basic design of the Lockheed P-38 Lightning, the first in a series devoted to the aircraft. It covers its variants and missions, the reasoning behind the twin-boom configuration, the wing and flaps, sources of aerodynamic drag, the central nacelle and armament, with comparisons to the Messerschmitt Bf 110 and the de Havilland Mosquito.

The P-38 was Lockheed's response to a 1937 United States Army Air Corps proposal calling for a high-altitude interceptor capable of 360 mph (about 580 km/h) and able to climb to 20,000 feet (about 6,100 m) in six minutes; Lockheed further aimed to exceed 400 mph. The company had never built a combat aircraft: its experience came from fast civilian aircraft like the Vega and the 1935 twin-engine Model 10 Electra, which flew at about 195 mph. Since no engine allowed a single-engine fighter to reach that speed, two Allison V-1710s were used instead. Kelly Johnson's sketches show several discarded configurations. The need for turbochargers, which the Army Air Corps favored following an NACA report and which the Allison required to perform at altitude, forced each boom to house an engine, turbo, main landing gear, radiators and other equipment; the booms ended up so long that extending them to the tail was a natural step, as chief engineer Hall Hibbard explained in 1944.

Besides the fighter version, there were photo-reconnaissance variants, a two-seat night fighter with radar, a bomber with a glazed nose and Norden bombsight, a radar-equipped variant for bombing through clouds, torpedo trials, and a medevac configuration carrying two patients in external pods; it could carry 4,000 pounds of bombs. The wing uses the NACA 23016 airfoil, the same as the Douglas DC-4, with Fowler flaps that greatly reduced stall speed: 94 and 69 mph indicated at 15,000 pounds according to the manuals, and 112 and 88 mph calibrated in tests at 14,800 pounds. G models and later had a maneuvering position on the flap lever. The exposed turbos and numerous cooling intakes gave it a lot of drag: a P-38D with 1,150 hp per engine reached 322 mph at 5,000 feet. It was the first American fighter with flush-riveted skin. The nacelle houses four .50-caliber machine guns with up to 500 rounds each and a 20 mm cannon with 150, staggered to avoid jamming, and the design made for a simpler tricycle landing gear.