Pratt &amp; Whitney XT57Pratt &amp; Whitney XT57 Pratt & Whitney XT57 The Pratt & Whitney XT57 (company designation: PT5) was an axial-flow turboprop engine developed by Pratt & Whitney in the mid-1950s. The XT57 was developed from the Pratt & Whitney J57 turbojet. Design and development. One XT57 (PT5), a turboprop development of the J57, was installed in the nose of a JC-124C (BuNo 52-1069), and tested in 1956. Rated at , the XT57 was the most powerful turboprop engine in existence at the time, and it remains the most powerful turboprop ever built in the United States. The engine had a split-compressor design. Intended for use on the  Douglas C-132 aircraft, the XT57 turboprop used a Hamilton Standard Model B48P6A propeller with a diameter of , which was the largest diameter propeller to be used in flight at the time. The single-rotation propeller had four hollow steel blades, a maximum blade chord of , a length of , and a weight of . In the late 1950s, the XT57 was studied for use in a United States Navy-proposed, nuclear-powered conversion of a Saunders-Roe Princess flying boat. Despite not having entered service, the engine was selected because it had passed a Pratt & Whitney 150-hour testing program, which involved  running the engine for 5,000–7,000 hours. Engines on display. The XT57 engine is on display at the Pratt & Whitney museum in East Hartford, Connecticut. Pratt & Whitney XT57 The Pratt & Whitney XT57 (company designation: PT5) was an axial-flow turboprop engine developed by Pratt & Whitney in the mid-1950s. The XT57 was developed from the Pratt & Whitney J57 turbojet. Design and development. One XT57 (PT5), a turboprop development of the J57, was installed in the nose of a JC-124C (BuNo 52-1069), and tested in 1956. Rated at , the XT57 was the most powerful turboprop engine in existence at the time, and