Republic P-43 Lancer - Design and Development

Design and Development

The Seversky Aircraft Company, which in 1939 changed its name to Republic, constructed a range of private venture, one-off variants of its P-35 design, featuring different powerplants and enhancements, designated AP-2, AP-7, AP-4 (which flew after the AP-7), AP-9, XP-41. The series included a carrier-based version designated the NF-1 (Naval Fighter 1) that was also built. The most significant of these was the AP-4, which served as the basis for future Seversky/Republic aircraft. It featured fully retractable landing gear, flush riveting, and, most significantly, a Pratt & Whitney R-1830-SC2G engine with a belly-mounted turbo-supercharger, producing 1,200 hp (890 kW) and good high-altitude performance. The turbo-supercharger had been refined by Boeing as part of the development program for the B-17 Flying Fortress, and the improved performance it offered was of great interest to other aircraft manufacturers.

The XP-41 and sole AP-4 were nearly identical, although the AP-4 was initially fitted with a large prop spinner and a tight-fitting engine cowling, as a testbed to evaluate means of improving the aerodynamics of radial-engined fighters, following similar experiments with the first production P-35. The AP-4's big spinner was later removed and a new tight cowling fitted. Unsurprisingly, these measures led to overheating problems. On 22 March 1939, the engine caught fire in flight, the pilot had to bail out, and the AP-4 was lost. Despite the loss of the prototype, the USAAC liked the turbo-supercharged AP-4 demonstrator enough to order 13 more in May 1939, designating them YP-43.