The Insane Engineering of the P-38 Lightning

Video from the channel Real Engineering about Lockheed P-38 Lightning, linked on its Above Ten Thousand entry. Duration: 26:44. Language: English. Video type: Documentary.

The video analyzes the engineering solutions of the Lockheed P-38 Lightning, the twin-engine, twin-boom fighter designed under Kelly Johnson's direction, and reviews its technical limits and its role in World War II, using Operation Vengeance as an example.

The aircraft answered Circular Proposal X-608 from the US Army Air Corps, which called for a high-altitude interceptor capable of reaching 580 km/h and climbing to bomber cruising altitude in six minutes. No American engine of the 1930s was powerful enough on its own, and the specification limited single-seat pursuit fighters to one engine, so Johnson studied numerous twin-engine configurations before choosing a central engineless nacelle between two booms. It was Lockheed's first military production contract. Johnson was 27 at the time; he would later head Skunk Works and design the U-2 and the SR-71.

The central nacelle housed, in the nose, four .50-caliber machine guns and a 20 mm cannon firing forward, which avoided the convergence problems of wing-mounted guns. Each boom housed a twelve-cylinder, liquid-cooled Allison V-1710 V-engine with a General Electric turbocharger that supplemented the standard mechanical supercharger. The compressed air was cooled in an intercooler built into the wing's leading edge, which added almost no drag but fell short once engine power increased during the war. This system performed worse than the Merlin's two-stage, two-speed superchargers, though around 20,000 feet the P-38 slightly outperformed the Spitfire. It was among the first fighters with tricycle landing gear, an advantage on the improvised airstrips of the Pacific. In April 1943, 16 P-38s intercepted the aircraft carrying Admiral Yamamoto near Bougainville: a round trip of about 1,600 km, made possible by its range with drop tanks. Both transport bombers were shot down. Its main flaw was a very low critical Mach number in a dive, which left the controls unresponsive and was mitigated with dive flaps under the wings.