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General Electric T700 / CT7



The General Electric T700 and CT7 are a family of turboshaft and turboprop engines in the 1,500-3,000 shp class.

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 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 is based on the CT7-8A engine. Compared with the T700 powering H-60 helicopters, the YT706 has a larger compressor, hot section improvements and a full authority digital engine control. The YT706 provides up to 30 percent more power than the current T700-701C and will increase the hot-and-high mission capability of the MH-60M Black Hawk procured by the U.S. Army for its Special Operations applications.



T700: Military turboshaft engine.
YT700: Prototype version.
T700-700: Initial T700 variant. The improved T700-GE-701A, -701B, -701C,-701D versions have also been developed fro the original -700.
T700-TEI701D: Licensed produced version of Tusaş Engine Industries of Turkey. Developed for use in the Sikorsky/Turkish Aerospace Industries T-70 Utility Helicopter.

CT7 turboshaft: Commercial version of T700.
CT7-2A : Basic model
CT7-2D : Higher flow compressor and surface coatings to improve resistance to wear and corrosion
CT7-2D1 : Similar to the CT7-2D but uses a CT7-6 type hot section

CT7 turbprop: Turboprop version of CT7.



T700/CT7 turboshaft
AgustaWestland AW101
AgustaWestland AW149
AgustaWestland AW189
AgustaWestland CH-149 Cormorant
Bell 214ST
Bell 525
Bell AH-1W SuperCobra
Bell AH-1Z Viper
Bell UH-1Y Venom
Boeing AH-64 Apache
Kaman SH-2G Super Seasprite
Lockheed Martin VH-71 Kestrel
Mitsubishi H-60
NHIndustries NH90
Piasecki X-49
Sikorsky CH-148 Cyclone
Sikorsky HH-60 Jayhawk
Sikorsky HH-60 Pave Hawk
Sikorsky SH-60 Seahawk
Sikorsky UH-60 Black Hawk
Sikorsky S-70
Sikorsky S-92
Sikorsky S-97


CT7 turboprop
Let L-610G
Saab 340
Sukhoi Su-80



Type: Turboshaft
Length: 47 in (T700-GE-700/701 series) to 48.2 in (T700/T6A)
Diameter: 25 in / 26 in (T700/T6E)
Dry weight: 400 lb (YT700-GE-700); 437 lb (T700-GE-700); 537 lb (T700/T6E)
Compressor: 6 stage-5 stage axial, 1 stage centrifugal.
Combustors: Annular
Turbine: 2 stage gas generator and 2 stage power turbine
Fuel type: JP-4 or JP-5 (YT700-GE-700)
Oil system: self contained, pressurized, recirculating dry sump
Maximum power output:
YT700-GE-700:1,536 shp (1,145 kW);
T700-GE-700: 1,622 shp (1,210 kW);
T700/T6E: 2,380 shp (1,775 kW);
YT706-GE-700: 2,638 shp (1,967 kW)
Overall pressure ratio: 17x
Specific fuel consumption: 0.433 (T700/T6E) to 0.465 (T700-GE-701A)
Power-to-weight ratio: 3.84 shp/lb (YT700-GE-700); 3.71 shp/lb (T700-GE-700); 4.48 shp/lb (T700/T6E)



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