The Boeing KC-135 Stratotankers were all originally powered by turbojet engines. A JT3D powered 707-123B and 720-023B (the suffix B was to indicate a turbofan powered aircraft) entered service with American Airlines on the same day, March 12, 1961. The earlier 707s had been powered by the turbojet JT3C and the improved efficiency of the turbofan soon attracted the airlines. In 1959, important orders for the engine were the Boeing 707-120B and Boeing 720B when American Airlines ordered one 707 powered by JT3D turbofans and KLM ordered a JT3D powered Douglas DC-8. Pratt & Whitney provided a kit whereby JT3Cs could be converted to the JT3D standard in an overhaul shop. On the Boeing 707 the JT3D fan nacelle was relatively short, whereas the Douglas DC-8 installation had a full length fan cowl. Instead P&W designed a 2-stage unit based on some research they had done to support the J91 nuclear turbojet. Unlike GE with the CJ805-23, Pratt & Whitney had not undertaken any transonic fan research prior to designing the JT3D, so they were unable to incorporate a single stage unit into the specification. On the LP turbine, the second stage was enlarged and a third stage added. A 2-stage fan replaced the first 3 stages of the 9-stage JT3C LP compressor. Most JT3D engines still in service today are used on military aircraft, where the engine is referred to by its USAF designation of TF33.Īware of the competition from the Rolls-Royce Conway turbofan, Pratt & Whitney decided to develop the JT3D turbofan from the JT3C turbojet for later deliveries of the Boeing 707 and the Douglas DC-8, then nearing entry into service. Over 8,000 JT3Ds were produced between 19. It was first run in 1958 and was first flown in 1959 under a B-45 Tornado test aircraft. The Pratt & Whitney JT3D is an early turbofan aircraft engine derived from the Pratt & Whitney JT3C turbojet.
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