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 civil aircraft, such as the Lockheed L-188 Electra and the Tupolev Tu-95, have also used turboprop power. The Airbus A400M is powered by four Europrop TP400 engines, which are the third most powerful turboprop engines ever produced, after the eleven megawatt-output Kuznetsov NK-12 and 10.4 MW-output Progress D-27. In 2017, The most widespread turboprop airliners in service were the ATR 42/72 (950 aircraft), Bombardier Q400 (506) and Dash 8-100/200/300 (374), Beechcraft 1900 (328), de Havilland Canada DHC-6 Twin Otter (270), Saab 340 (225). Less widespread and older airliners include the BAe Jetstream 31, Embraer EMB 120 Brasilia, Fairchild Swearingen Metroliner,