|T700 / CT7|
|National origin||United States|
|Major applications||Bell AH-1W SuperCobra |
Bell AH-1Z Viper
Bell UH-1Y Venom
Boeing AH-64 Apache
KAI KUH-1 Surion
Sikorsky UH-60 Black Hawk
Sikorsky SH-60 Seahawk
|Number built||Over 20,000|
|Developed into||General Electric T901|
In 1967, General Electric began work on a new turboshaft engine demonstrator designated the "GE12" in response to US Army interest in a next-generation utility helicopter. The GE12 was designed and conceived by GE's Art Adamson and Art Adinolfi. In 1967, both GE and Pratt & Whitney were awarded contracts to work parallel with each other to design, fabricate, and test the technology. The Army effort led, in the 1970s, to development of the Sikorsky S-70 Black Hawk, powered by twin GE "T700" turboshafts, the production descendant of the GE12.
The T700 was initially bench-tested in 1973, passed military qualification in 1976, and went into production in 1978. The initial "T700-GE-700" is an ungeared free-turbine turboshaft, with a five-stage axial / one-stage centrifugal mixed-flow compressor, featuring one-piece "blisk" axial stages, with the inlet guide vanes and first two stator stages variable; an annular combustion chamber with central fuel injection to improve combustion and reduce smoke; a two-stage compressor turbine; and a two-stage free power turbine with tip-shrouded blades. The engine is designed for high reliability, featuring an inlet particle separator designed to spin out dirt, sand, and dust. The T700-GE-700 is rated at 1,622 shp (1,210 kW) intermediate power.
The T700-GE-700 was followed by improved and uprated Army engine variants for the UH-60 Black Hawk and the AH-64 Apache helicopters, as well as marinized naval engine variants for the SH-60 Seahawk derivative of the Black Hawk, the SH-2G Seasprite, and the Bell AH-1W Supercobra. T700s are also used on Italian and commercial variants of the AgustaWestland EH101/AW101 helicopter, and Italian variants of the NHIndustries NH90 helicopter. These are all twin-engine machines, except for the three-engined EH101.
The commercial version of the T700 is the "CT7", with the engine used on the Bell 214ST (an enlarged version of the Huey), commercial Black Hawks, and the Sikorsky S-92 derivative of the Black Hawk, all of which are twin-engine helicopters.
The CT7 turboprop variants use the same core as the turboshaft variants, with a propeller gearbox fitted forward of the core. CT7 turboprops are used on variants of the Swedish Saab 340 airliner, the Indonesian-Spanish Airtech CN-235 cargolifter, and the Czech Let L-610G airliner, all twin-turboprop aircraft. The baseline CT7-5A provides 1,735 shp (1,294 kW) on takeoff.
In the late 1980s, GE also proposed a much larger turboprop, the T407/GLC38, with a five-stage axial/one-stage centrifugal mixed-flow compressor, an annular combustor with 15 burners; a two-stage compressor turbine, a three-stage power turbine, and max takeoff power of 6,000 shp (4,475 kW).
The YT706 engine is based on the CT7-8A engine. Compared with the H-60's primary T700 engine, the T706 has a larger compressor, hot section improvements, and full authority digital engine control. The T706 is rated at 2,600 shp (1,939 kW) and increases the hot-and-high mission capability of the U.S. Army's MH-60M Black Hawk for Special Operations applications.
T700: Military turboshaft engine.
CT7 turboshaft: Commercial version of T700.
CT7 turboprop: Turboprop version of CT7.
The initial version of this article was based on a public domain article from Greg Goebel's Vectorsite.
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