Pratt & Whitney JT4A

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Part of an Pratt & Whitney J75 of a shot down Lockheed U-2 in Cuba
Part of an Pratt & Whitney J75 of a shot down Lockheed U-2 in Cuba

The Pratt & Whitney JT4A was an axial-flow turbojet engine of the late 1950s. A two-spool turbojet in the 17,000 lbf (76 kN) thrust class, it was essentially the bigger brother of the Pratt & Whitney JT3C.

Before the arrival of the Pratt & Whitney JT3D turbofan engine, the JT4A was used to power certain Boeing 707s and Douglas DC-8s models. It was used to improve field performance in the medium-range Boeing 707-220 and Douglas DC-8-20, and to achieve intercontinental range in the original Boeing 707-320 and the Douglas DC-8-30. In military use the JT4A engine had the designation J75, which was used on the Lockheed U-2, A-12 OXCART, the Republic F-105 Thunderchief, the Convair F-106 Delta Dart. It was also utilized in the prototype and experimental North American YF-107, Chance-Vought XF8U-3 Crusader III, P6M SeaMaster, and Avro Arrow.