Taking advantage of this effort, the US Navy awarded Allison a contract for the design and development of a 4,100 shp (3,057 kW) turboprop engine.

[1] The T38-A-1 power sections each contained 17-stage compressors giving a pressure ratio of 6.3:1, eight combustion chambers, and four-stage turbines.

[1] Accessories included a Master Control Unit, mounted above the compressors, and an air driven starter on the gearbox.

One unusual problem was discovered during ground running of the Republic XF-84H Thunderscreech turboprop powered fighter; the special transonic 3-bladed single propeller set up harmonics that proved to be harmful to humans within a certain distance from the aircraft.

As the individual power plants were clutched into the gearbox, it was intended in most instances that the aircraft could cruise on one half of the engine and only engage the second power-section when there was need.

Failure to recognize that one of the T38s had failed, and its compressor was devouring power produced by the other section, led to the loss of the first prototype Douglas XA2D-1 and its pilot on 14 December 1950.

[1] The T40 was also fitted to the North American A2J-1 Super Savage but the poor performance of the aircraft and continuing difficulties with the engines forced cancellation in favour of the Douglas A-3 Skywarrior.

[1] Limited flying was carried out by the two Republic XF-84H Thunderscreech turboprop fighter aircraft, but the continuing difficulties with the T40 engine, supersonic propeller, not to mention performance completely overshadowed by contemporary rivals led to cancellation of production plans.