The General Electric J85 is a compact turbojet used in trainers, light fighters, attack aircraft and unmanned decoys. Design studies began in late 1953, and the prototype ran in January 1956. Its combination of low weight and useful thrust gave it applications far beyond its initial missile programme.[1]
Decoy origins
The US Air Force funded development for the GAM-72 Quail, an air-launched decoy carried by the B-52. The decoy was intended to confuse enemy radar about the location of the bomber. The J85 first flew in the missile in August 1958, followed the next month by a crew-rated application in the prototype T-39 Sabreliner.[2][1]
Small-engine architecture
The Smithsonian's non-afterburning J85-GE-17A has an eight-stage axial compressor, annular combustor and two-stage axial turbine on a single shaft. It weighs 398 lb and produces 2,850 lbf at 16,500 rpm. This version powered the Cessna A-37 attack aircraft, while other members of the family incorporated afterburning for higher-performance roles.[1]
Training and fighter service
Afterburning J85s powered the Northrop T-38 Talon and F-5 Freedom Fighter. The T-38 brought supersonic performance to pilot training, while the F-5 carried the small engine into widespread international fighter use. GE also developed civil derivatives, including the CJ610 turbojet and CF700 turbofan, which found applications in early business aircraft.[1][2]
Extending operating life
Production of J85s and their commercial derivatives ended in 1988 after more than 12,000 deliveries. Support and improvement continued: a 2001 Air Force contract covered upgrade kits for 1,202 T-38 engines. The package included a redesigned compressor rotor and stator assembly, improved high-pressure turbine and new afterburner liner. These changes extended the usefulness of existing engines rather than requiring a completely new propulsion installation.[2]