Early flight tests of the first General Electric turbojet engine, the Type I-A, clearly showed the need for more powerful engines. GE followed with two designs of increased thrust. The second, known as the J31, had 7,118 N (1,600 lb) of thrust and first ran in April 1943. About 250 were built, mainly for the Bell YP-59 and P-59A and B jet aircraft.
This engine, a J31-GE-4, was a Navy version of the engine used in the Ryan FR-1 aircraft. It was similar to the -5 and -7 Air Force versions, except for the elimination and relocation of some accessories, and the rearrangement of engine supports.