The Pratt & Whitney J75 is an axial-flow turbojet engine first flown in 1955. A two-spool design in the 17,000 lbf (76 kN) thrust class, the J75 was essentially the bigger brother of the Pratt & Whitney J57 (JT3C). It was known in civilian service as the JT4A, and in a variety of stationary roles as the GG4 and FT4.
Pratt & Whitney J75
A US Navy J75 used in the P6M-2 Seamaster
The Pratt & Whitney J57 is an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 was the first 10,000 lbf (45 kN) thrust class engine in the United States. It was also the first two-spool turbojet to run, a few months before the similar Bristol Olympus in the UK.
Pratt & Whitney J57
J57s on a B-52D
JT3Cs installed on a Boeing 707-123
Pratt & Whitney JT3 (1/4th scale)