Pratt & Whitney J75

The Pratt & Whitney JT4 ( military designation Pratt & Whitney J75 ) is a jet engine from the American manufacturer Pratt & Whitney. It is a two-shaft turbojet in axial type. Between 1956 and 1967 it was produced in larger series.

The development began in 1951 and lasted until 1954. Goal was to create a powerful drive for the supersonic aircraft of the first generation of U.S. Navy and Air Force. In its basic construction and components for control, fuel supply and lubrication it was like the smaller Pratt & Whitney J57. The fuel is injected through fuel nozzles in each of six, eight individual, which is arranged around the compressor casing internal pipes. The military version could be supplied both with and without afterburner. To further improve performance water injection was possible.

The engine was first produced for the Republic F -105 in large series, but was also used in the F- 106 and the Lockheed U-2 used. The first flight with a Pratt & Whitney YJ75 -P -3 found in 1955 in an F -105 instead. This pre-production sample yielded a dry thrust of 71.2 kN. The most powerful production engine J75 -P - 19W was equipped with an afterburner and water injection from already 118 kN thrust. The total length of this design was 6.1 m with an afterburner and thrust tube. Is started the engine with compressed air, but also has a pyrotechnic starter device which can be operated by the pilot. Thus, the necessary starting speed can be achieved within 10 s.

The civil version received its approval for commercial aviation by the FAA in March 1957. It was used on the Boeing 707-220 and -320 and in the Douglas DC-8- 20 and -30. All civilian engines were delivered without afterburner.

Technical data ( JT4A -9)

  • Low-pressure compressor: eight steps
  • High-pressure compressor: seven steps
  • High-pressure turbine: a step
  • Low-pressure turbine: two stages
  • Diameter: 1092 mm
  • Length: 3680 mm
  • Weight: 2291 kg
  • Thrust: 74.7 kN at 8000 min-1
  • Pressure ratio 12:1
  • Air mass flow rate: 113 kg / s

Swell

  • " Jane's All the World 's aircraft" 1969/70
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