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General Electric TF39

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Title: General Electric TF39  
Author: World Heritage Encyclopedia
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Subject: Lockheed C-5 Galaxy, GE Aviation, Pratt & Whitney JT9D, General Electric T31, General Electric J97
Collection: General Electric Aircraft Engines, High-Bypass Turbofan Engines
Publisher: World Heritage Encyclopedia

General Electric TF39

A TF39 on a C-5 Galaxy at ILA (Internationale LuftfahrtAusstellung) in Berlin, 2008
Type Turbofan
Manufacturer GE Aviation
First run 1964
Major applications Lockheed C-5 Galaxy
Variants General Electric CF6
Developed into General Electric LM2500

The General Electric TF39 is a high-bypass turbofan engine. Developed to power the Lockheed C-5 Galaxy, it was the first high-power, high-bypass jet engine available. The TF39 was developed into the CF6 series of engines, and formed the basis of the General Electric LM2500 marine and industrial gas turbine.


  • Development 1
  • Design 2
  • Applications 3
  • Specifications (TF39-1C) 4
  • See also 5
  • References 6
  • External links 7


The United States Air Force opened the "CX-X Program" in 1964, intending to produce a next-generation strategic airlifter. Of the several airframe and engine proposals returned for consideration, Lockheed's aircraft and General Electric's engine were selected for the new design in 1965.

The high-bypass turbofan was a huge leap in engine performance, offering a thrust of 43,000 pounds, while improving fuel efficiency by about 25%.[1] The TF39 had an 8-to-1 bypass ratio, 25-to-1 compressor pressure ratio, a 2,500 °F (1,370 °C) turbine temperature made possible by advanced forced-air cooling. The first engine went for testing in 1965. Between 1968 and 1971, 463 TF39-1 and -1A engines were produced and delivered to power the C-5A fleet.


TF39s on a C-5 Galaxy, from the rear

The TF39 was a revolutionary 1960s engine rated from 41,000 to 43,000 lbf (191 to 205 kN) of thrust. It incorporated new features for a turbofan engine such as:

These features, together with advances in core technology below, contributed to a significant improvemment in fuel efficiency over any engines available at the time.

The engine also included features developed from previous GE engines

  • Variable stator vanes (used in the J79/CJ805[2])
  • Turbine cooling techniques (advanced from the J93 used in the XB-70[2])
  • Cascade-type thrust reverser (from the CJ805[2])
  • Snubbered first stage fan blades (snubbers (mid-span shrouds)introduced by GE on the YJ93 first stage compressor blades[3])

The fan was a unique, very complex design;[3] the first stage extends to about half the second stage annulus[4] and runs in a tip shroud. The blades are snubbered. 'Snubbers' are protuberances that stick-out at right angles to the fan aerofoil at mid[3] to 2/3 span.[5] At speed the snubbers on adjacent fan blades butt-up against each other to prevent blade failures due to flutter.[5] This particular aspect of the design, together with the second stage inlet guide vanes in the outer half of the duct, is seen looking in the engine intake.[6][7]

The fan second stage has a mid-span platform/flow splitter which separates the single-stage outer annulus from the 2-stage inner annulus.[4] The inner portions of the first and second stage blades provide supercharging for the 16-stage compressor.[8]

The high bypass ratio of 8:1 for the TF-39 had its origins in the lift-fan technology demonstrated by GE in the XV-5 Vertifan aircraft.[2] This aircraft had two X353-5 engines each consisting of a 62.5 in. diameter[9] lift-fan driven by a gas generator (J85). The bpr in VTOL operation was 12.3.[10] This tip-turbine driven lift-fan concept was turned 90 degrees and developed as an 80in. diameter "cruise fan" demonstrator, driven by a J79 gas generator.[2] For the CX-X program GE demonstrated a half-scale engine, the GE1/6, with 15,830 lb thrust and an sfc of 0.336.[11] This was developed into the TF39 with a 97 in.[4] fan.


  • Lockheed C-5A/B/C Galaxy

Specifications (TF39-1C)

Data from [12]

General characteristics

  • Type: Turbofan
  • Length: 312 in (792 cm)
  • Diameter: 97 in (246 cm)
  • Dry weight: 8000 lb (3630 kg)


  • Compressor: Axial, 2 stage fan, 16 stage high pressure compressor
  • Combustors: Annular
  • Turbine: Axial, 2 stage high pressure turbine, 6 stage low pressure turbine.


See also

Related development
Comparable engines
Related lists


  1. ^ General Electric - CF6 history
  2. ^ a b c d e "seven decades of progress" General Electric, ISBN 0-8168-8355-6, Aero Publishers Inc. p.152
  3. ^ a b c "Gas Turbine Technology Evolution: A Designer's Perspective" Bernard L. Koff, Journal of Propulsion and Power, Vol.20 No. 4, July–August 2004, p.591
  4. ^ a b c "Flight Manual USAF Series C5A and C5B Airplanes", TO 1C-5A-1, Lockheed Martin Corporation
  5. ^ a b "Flutter and Resonant Vibration Characteristics of Engine Blades" A.V. Srinivasan, 97-GT-533, ASME, p.8
  6. ^ - TF39 front view
  7. ^ - TF39 running
  8. ^ "Aviation Week" 16 August 1965, shown as Figure 35 in "The History Of The Rolls-Royce RB211 Turbofan Engine", ISBN 978-1-872922-48-5, The Rolls-Royce Heritage Trust
  9. ^ "Aerodynamic characteristics of a Large-Scale Model with a High Disk Loading Lift Fan Mounted in the Fuselage" Aoyagi, Hickey and deSavigny, NASA TN D-775
  10. ^ "Jet Propulsion for Aerospace Applications" Second Edition,Hesse and Mumford,Pitman Publishing Corporation, 1964, Table 11.1
  11. ^ "The Development of Jet and Turbine Engines", 4th edition, Bill Gunston, ISBN 0 7509 4477 3, p.192
  12. ^ Gas Turbine Engines. Aviation Week & Space Technology Source Book 2009. p. 119
  • Gunston, Bill (2006). World Encyclopedia of Aero Engines, 5th Edition. Phoenix Mill, Gloucestershire, England, UK: Sutton Publishing Limited.  

External links

  • General Electric TF39 website
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