General Electric T700

The General Electric T700 and CT7 are a family of turboshaft and turboprop engines in the 1500-3000 shp class.

Development

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 1,210 kW (1,622 SHP) 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 Kaman SH-2G Super Seasprite, and the Bell AH-1W Supercobra. T700s are also used on Italian and commercial variants of the AgustaWestland EH101 helicopter, and Italian variants of the NHI 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. There are also turboprop versions of the CT7.

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 1,294 kW (1,735 SHP) 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 4,475 kW (6,000 SHP).

The YT706 is based on the CT7-8A engine.cite web |url=http://www.geae.com/aboutgeae/presscenter/military/military_20070813.html |title=GE YT706 Production Contract Awarded by US Army |accessdate=2007-08-16 |date=2007-08-13 |publisher=GE Aviation ] Compared with the T700 currently 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.

Applications

T700

* AH-1W/Z Supercobra
* SH-2G Super Seasprite
* UH-1Y Venom
* UH-60 Black Hawk
* SH-60 Seahawk
* AH-64 Apache
* HH-60 Jayhawk
* CH-148 Cyclone
* AgustaWestland EH101/CH-149 Cormorant/VH-71 Kestrel
* NHI NH90
* Piasecki X-49

CT7 turboshaft

* Bell 214ST
* Sikorsky S-70C
* Sikorsky S-92

CT7 turboprop

* CASA/IPTN CN-235
* Saab 340
* Sukhoi S-80

pecifications (T700)

pistonspecs

type=Turboshaft
length=47in (T700-GE-700/701 series) to 48.2in (T700/T6A)
diameter=25in / 26in (T700/T6E)
weight=437lb (T700-GE-700) to 537lb (T700/T6E)
compressor=6 stage-5 stage axial, 1 stage centrifugal.
combustion=Annular
turbine=
fueltype=
oilsystem=
power=1,622 shp (T700-GE-700) to 2,380 shp (T700/T6E)
thrust=
compression=17x
aircon=
turbinetemp=
fuelcon=
specfuelcon=0.433 (T700/T6E) to 0.465 (T700-GE-701A)
power/weight=3.71 shp/lb (T700-GE-700) to 4.48 shp/lb (T700/T6E)
thrust/weight=

References

External links

* [http://geae.com/engines/corporate/cfe738.html General Electric CFE738 page] at [http://geae.com GE Aviation corporate website]
* [http://www.geae.com/engines/military/comparison_turboshaft.html GE Turbine Comparison Chart]
* [http://www.faqs.org/docs/air/v2003m10.html Vectors by Greg Goebel]