Capital Airlines Lockheed Constellations. In 1955 they became the first U.S. operator of the British manufactured, four engine Vickers Viscount, the first passenger turboprop airliner. The Viscount propjets were deployed on the flagship Washington-Chicago route and the airline had planned to fly them on expanded service; however, Capital was mostly stymied by the federal Civil Aeronautics Board (CAB). The CAB also refused Capital a requested subsidy. Still, Capital's passenger-miles in 1957 were 88% more than 1955. On November 14, 1956 a Capital pilot reported seeing a blue-white ball in the sky. The pilot, Captain William J. Hull, was a senior captain who
Turboprop a turboshaft. Alan Arnold Griffith had published a paper on turbine design in 1926. Subsequent work at the Royal Aircraft Establishment investigated axial turbine designs that could be used to supply power to a shaft and thence a propeller. From 1929, Frank Whittle began work on centrifugal turbine designs that would deliver pure jet thrust. The world's first turboprop was designed by the Hungarian mechanical engineer György Jendrassik. Jendrassik published a turboprop idea in 1928, and on 12 March 1929 he patented his invention. In 1938, he built a small-scale (100 Hp; 74.6 kW) experimental gas turbine. The larger Jendrassik