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Allison YT-56-A-3 Turboprop

DAYTON, Ohio -- Allison YT-56-A-3 on display in the Research & Development Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)

DAYTON, Ohio -- Allison YT-56-A-3 on display in the Research & Development Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)

The T-56, a jet engine that uses a propeller to produce most of its thrust, was originally designed to power the Lockheed C-130 Hercules. Because the T-56 compressor and turbine rotate at a high speed (13,820 rpm), a reduction gearbox is used to allow the propeller to turn at a much slower, more efficient speed. The production T-56 engine delivers approximately 4,000 hp to the propeller, while an additional 800 pounds of thrust is produced by the jet exhaust. Its maximum operating altitude is 55,000 feet.

The T-56 evolved from Allison's T-38 engine and was first flown in the nose of a B-17 test-bed aircraft in 1954. The engine on display is a prototype of later engines in the T-56 series.

TECHNICAL NOTES:
Compressor: 14-stage axial
Turbine: 4-stage axial
Gear reduction ratio: 12.5 to 1
Weight (without propeller): 1,610 lbs.
Maximum operating altitude: 55,000 ft.
Cost: $150,000

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