Pratt & Whitney XT57

The Pratt & Whitney XT57, company designation PT5, was an axial-flow turboprop engine that Pratt & Whitney developed in the mid-1950s from its J57 turbojet. It used a split-compressor, two-spool design and was rated at 15,000 shaft horsepower, which made it the most powerful turboprop engine in existence at the time and the most powerful ever built in the United States. It was intended for the Douglas C-132 transport and drove a Hamilton Standard propeller about 20 feet in diameter, the largest used in flight at the time. One engine was installed in the nose of a Douglas JC-124C testbed and tested in 1956, and it passed a 150-hour test program, but it never entered service. In the late 1950s it was also studied for a proposed nuclear-powered conversion of the Saunders-Roe Princess flying boat.