Allison YJ71-A-4 Turbojet Engine

Type: Turbojet

Thrust: 57,824 N (13,000 lb) at 6,100 rpm

Compressor: 16-stage axial

Combustor: Single annular

Turbine: 3-stage axial

Weight: 2,030 kg (4,476 lb)

Begun in 1949, the J71 was the first turbojet wholly developed by Allison, drawing on the company's technology base from its uprating of the J33 and J35 turbojets, and development of the T38 and T40 turboprops.

The J71 was used during the 1950s in the initial version of Northrop's S-62 intercontinental missile, early versions of Martin's XP6M-1 flying boat, McDonnell F3H-2N fighter, and Douglas B-66 bomber. However, it could not penetrate the high-performance combat aircraft marketplace dominated by the more technically advanced GE J79 and P&W J57 turbojets, which were lighter and had better fuel economy. With phase out of the F3H program, failure to attract further aircraft, and no new orders in sight, Allison dropped the program in the late 1950s after producing 1,707 engines.

This flight-test engine was one of four that powered the prototype Martin XP6M-1 Seamaster, was similar to the J71-A-2, but had a single air intake and short afterburner for takeoff.