Armstrong Whitworth Apollo Armstrong Whitworth Apollo The Armstrong Whitworth AW.55 Apollo was a 1940s British four-engine turboprop airliner built by Armstrong Whitworth at Baginton. The aircraft was in competition with the Vickers Viscount but was beset with engine problems and only two were built. The requirement resulted from the Brabazon Committee's Type II design, calling for a small, medium-range pressurized aircraft to fly its less-travelled routes which became Air Ministry Specification C.16/46 for an aircraft able to carry 24-30 passengers over 1,000 mi (1,610 km) at a cruising speed of . The resulting design was the AW.55 Apollo, a low-wing cantilever monoplane with
Turboprop in the experimental Consolidated Vultee XP-81. The XP-81 first flew in December 1945, the first aircraft to use a combination of turboprop and turbojet power. The technology of the Allison's earlier T38 design evolved into the Allison T56, with quartets of the T56s being used to power the Lockheed Electra airliner, its military maritime patrol derivative the P-3 Orion, and the widely produced C-130 Hercules military transport aircraft. One of the most produced turboprop engines used in civil aviation is the Pratt & Whitney Canada PT6 engine. The first turbine-powered, shaft-driven helicopter was the Kaman K-225, a development of Charles