Pratt & Whitney JT3D

The Pratt & Whitney JT3D is an early turbofan engine derived from the JT3C turbojet. It was first run in 1958, first flown in 1959 under a B-45 Tornado test aircraft, and more than 8,000 were built between 1959 and 1985. Pratt & Whitney developed it to answer the Rolls-Royce Conway for later Boeing 707 and Douglas DC-8 deliveries, replacing the first three stages of the JT3C low-pressure compressor with a two-stage fan and adding a third low-pressure turbine stage. American Airlines put the JT3D-powered 707-123B and 720-023B into service on 12 March 1961. In military service it is designated TF33, and it powers the Boeing B-52H Stratofortress and re-engined KC-135 tankers, among other aircraft. A JT3D-8A is rated at 17,000 lbf (76 kN) for take-off with a bypass ratio of 1.42 to 1.