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Williams International F-121 Fanjet

DAYTON, Ohio -- Williams International F-121 Fanjet on display in the Research & Development Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)

DAYTON, Ohio -- Williams International F-121 Fanjet on display in the Research & Development Gallery at the National Museum of the United States Air Force. (U.S. Air Force photo)

Note: This item is currently in storage.

The advent of small jet-propelled aircraft challenged engine manufacturers to provide propulsion systems for them. When an engine was required to propel unmanned aircraft, such as the AGM-136A Tacit Rainbow, on a one-way trip to a target, they faced the added challenge of designing a "throwaway" engine. It had to have a long "shelf-life" but a short life expectancy -- once started -- of about three hours. Williams International responded with the F-121, one of the smallest engines of its type ever built and flown in an aircraft.

The F-121 first flew in an AGM-136A on July 30, 1984. Since the engine could not be started until after the vehicle left its parent aircraft, it had a pyrotechnic (cartridge) starter. Flight test experience proved it to be a relatively trouble-free engine. Out of 32 free-flight test missions, not one was impaired by an F-121 engine problem.

While the display engine obviously never flew a Tacit Rainbow test mission, it was used in many "bench" tests before being retired to the museum in February 1993.

TECHNICAL NOTES:
Model:
F-121
Length: 40 in.
Diameter: 8 1/2 in. 
Weight: 49 lbs.
Compressor: 6-stage axial
Turbine: 2-stage axial 
Fan by-pass ratio: 1.7:1
Thrust: Approx. 70 lbs. at 45,000 rpm

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