General Electric T700

T700 / CT7
Type	Turboshaft
National origin	United States
Manufacturer	GE Aviation
First run	1973
Major applications	Bell AH-1W SuperCobra ; Bell AH-1Z Viper ; Bell UH-1Y Venom ; Boeing AH-64 Apache ; CASA/IPTN CN-235 ; KAI KUH-1 Surion ; Saab 340 ; Sikorsky UH-60 Black Hawk ; Sikorsky SH-60 Seahawk
Number built	Over 20,000
Developed into	General Electric T901

The General Electric T700 and CT7 are a family of turboshaft and turboprop engines in the 1,500–3,000 shp (1,100–2,200 kW) class.

Design and 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.^[2] 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.^[2] 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.^[2]

The T700 was initially bench-tested in 1973, passed military qualification in 1976, and went into production in 1978.^[3] 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.^[4] 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.^[5]

Variants

US Marines perform maintenance on the T700-GE-401C from a Bell UH-1Y helicopter

T700: Military turboshaft engine.

YT700: Prototype version.
T700-GE-700: Initial T700 variant.
T700-GE-701: The improved T700-GE-701A, -701B, -701C,-701D versions have also been developed from the original -700.^[6]
T700-GE-401: Navalised version for SH-60 Seahawk helicopters.
T700-GE-401C: Universal application version of the -401.
T700-GE-701C: Universal application version of the -701.
T700-TEI-701D: Licensed produced version of Tusaş Engine Industries of Turkey. Developed for use in the Sikorsky/Turkish Aerospace Industries T-70 utility helicopter.^[7]
T700-701K: First rear-drive version of the T700 family, a product from the joint development with Samsung Techwin (later became Hanwha Aerospace). Powering the KAI KUH-1 Surion with Hanwha's licensed production.^[8]

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
CT7-2E1: Leonardo Helicopters AW189
CT7-6/-6A: The CT7-6/-6A turboshaft engines are upgraded commercial variants of the successful T700/CT7 engine family. The turboshaft engine powers the entire development fleet of AgustaWestland AW101 helicopters with thousands of flight hours of operation.^[9]
CT7-8: The CT7-8 is a family of powerful engines in the 2,500 to 3,000 shp class. They are more powerful and more efficient versions of its predecessors.^[9]
CT7-8A: A version of the CT7-8 family used to power older Sikorsky S-92/H-92 helicopters.
CT7-8A1: A more fuel efficient version of the CT7-8A. It is used to power newer Sikorsky S-92/H-92 helicopters. The CT7-8A1 produces 2,520 shp.
CT7-8A5
CT7-8A7: Developed by GE as an uprated, more efficient and more reliable version of the CT7-8A1 engine for the Royal Canadian Air Force's Sikorsky CH-148 Cyclone helicopters. It is the most modern version of the CT7/T700 engine family. The CT7-8A7 produces 3,000 shp.
CT7-8B
CT7-8B5
CT7-8E
CT7-8E5
CT7-8E6
CT7-8F
CT7-8F5

CT7 turboprop: Turboprop version of CT7.

CT7-3: Compact shortened and lightened version.^[10]
CT7-5A2
CT7-5A3
CT7-7A
CT7-7A1
CT7-9B
CT7-9B1
CT7-9B2
CT7-9C
CT7-9C3
CT7-9D
CT7-9D2

Applications

A U.S. Navy Sailor performing maintenance on a T700 engine from a MH-60R Sea Hawk.

T700/CT7 turboshaft

YT706 turboshaft

CT7 turboprop

Specifications (T700)

General characteristics

Type: Turboshaft engine
Length: 47 in (1,200 mm) (T700-GE-700/701 series); 48.2 in (1,220 mm) (T700/T6A)
Diameter: 25 to 26 in (640 to 660 mm) (T700/T6E)
Dry weight:
- 400 lb (180 kg) (YT700-GE-700)
- 437 lb (198 kg) (T700-GE-700)
- 537 lb (244 kg) (T700/T6E)

Components

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

Performance

Maximum power output:
- YT700-GE-700: 1,536 shp (1,145 kW)^[11]
- 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)^[12]
Overall pressure ratio: 17:1
Specific fuel consumption: 0.433 lb/(hp⋅h) (263 g/kWh)^[13] (T700/T6E) to 0.465 lb/(hp⋅h) (283 g/kWh) (T700-GE-701A)^{[citation needed]}
Power-to-weight ratio:
- 3.84 shp/lb (6.31 kW/kg) (YT700-GE-700)
- 3.71 shp/lb (6.10 kW/kg) (T700-GE-700)
- 4.48 shp/lb (7.37 kW/kg) (T700/T6E)

References

^ Kover, Amy; Kellner, Tomas (December 16, 2019). "Stayin' Alive: Trusty GE Chopper Engine That Entered Service When The Bee Gees Ruled The Charts Wins New $1 Billion Lease On Life". GE Reports: Future of Flight. Retrieved May 15, 2021.
^ ^a ^b ^c Leyes, Richard A.; Fleming, William A. (1999). The History of North American Small Gas Turbine Aircraft Engines. AIAA. ISBN 9781563473326. Retrieved 5 October 2017.
^ "Unknown Title". Verti-flite, Volume 37. 1991. Retrieved 5 October 2017.
^ "GE YT706 Production Contract Awarded by US Army". GE Aviation. 2007-08-13. Archived from the original on 2007-10-23. Retrieved 2007-08-16.
^ "Sikorsky S-70A." (online subscription article) Jane's All the World's Aircraft, 25 May 2016.
^ "The General Electric T-700/T-701C". Archived from the original on 2014-05-02. Retrieved 2022-07-09.
^ "TEI TO POWER BLACKHAWKS |". www.tei.com.tr. Archived from the original on 2016-09-19. Retrieved 2016-09-17.
^ "T700-701K turboshaft engines datasheet" (PDF). GE Aerospace.
^ ^a ^b "The CT7 Engine - GE Aviation". www.geaviation.com.
^ John W.R. Taylor, ed. (1988). Jane's All the World's Aircraft 1988-89. London: Jane's Information Group. ISBN 0-7106-0867-5.
^ Govt Competitive Test UTTAS YUH-60A, USAAEFA Proj # 74-06-1
^ "GE YT706 Power Specifications". GE Aviation. Archived from the original on 2011-06-14. Retrieved 2011-06-02.
^ Peter deBock (September 18, 2019). GE turbines and small engines overview (PDF). ARPA-e INTEGRATE meeting. Global Research. General Electric.

U.S. Department of Transportation (USDOT), Federal Aviation Administration (FAA) (July 20, 2020). Type Certificate Data Sheet No. E8NE (PDF) (Report). Archived from the original (PDF) on July 16, 2021. Retrieved July 20, 2021.

The initial version of this article was based on a public domain article from Greg Goebel's Vectorsite.

External links

[GEReports20191216-1] Kover, Amy; Kellner, Tomas (December 16, 2019). "Stayin' Alive: Trusty GE Chopper Engine That Entered Service When The Bee Gees Ruled The Charts Wins New $1 Billion Lease On Life". GE Reports: Future of Flight. Retrieved May 15, 2021.

[HistoryBook-2] Leyes, Richard A.; Fleming, William A. (1999). The History of North American Small Gas Turbine Aircraft Engines. AIAA. ISBN 9781563473326. Retrieved 5 October 2017.

[3] "Unknown Title". Verti-flite, Volume 37. 1991. Retrieved 5 October 2017.

[YT706-4] "GE YT706 Production Contract Awarded by US Army". GE Aviation. 2007-08-13. Archived from the original on 2007-10-23. Retrieved 2007-08-16.

[Janes_S-70-5] "Sikorsky S-70A." (online subscription article) Jane's All the World's Aircraft, 25 May 2016.

[6] "The General Electric T-700/T-701C". Archived from the original on 2014-05-02. Retrieved 2022-07-09.

[7] "TEI TO POWER BLACKHAWKS |". www.tei.com.tr. Archived from the original on 2016-09-19. Retrieved 2016-09-17.

[8] "T700-701K turboshaft engines datasheet" (PDF). GE Aerospace.

[geaviation.com-9] "The CT7 Engine - GE Aviation". www.geaviation.com.

[JAWA88-89-10] John W.R. Taylor, ed. (1988). Jane's All the World's Aircraft 1988-89. London: Jane's Information Group. ISBN 0-7106-0867-5.

[11] Govt Competitive Test UTTAS YUH-60A, USAAEFA Proj # 74-06-1

[YT706_HP-12] "GE YT706 Power Specifications". GE Aviation. Archived from the original on 2011-06-14. Retrieved 2011-06-02.

[13] Peter deBock (September 18, 2019). GE turbines and small engines overview (PDF). ARPA-e INTEGRATE meeting. Global Research. General Electric.

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