The General Electric TF39 is a

high-bypass turbofan engine A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stag ...

that was developed to power the

Lockheed C-5 Galaxy The Lockheed C-5 Galaxy is a large military transport aircraft designed and built by Lockheed Corporation, Lockheed, and now maintained and upgraded by its successor, Lockheed Martin. It provides the United States Air Force (USAF) with a heavy ...

. The TF39 was the first high-power, high-bypass jet engine developed. The TF39 was further developed into the

CF6 The General Electric CF6, US military designations F103 and F138, is a family of high-bypass turbofan engines produced by GE Aviation. Based on the TF39, the first high-power high-bypass jet engine, the CF6 powers a wide variety of civilian a ...

series of engines, and formed the basis of the

LM2500 The General Electric LM2500 is an industrial and marine gas turbine produced by GE Aviation. The LM2500 is a derivative of the General Electric CF6 aircraft engine. As of 2004, the U.S. Navy and at least 29 other navies had used a total of more ...

and LM6000 marine and industrial gas turbine. On September 7, 2017, the last active C-5A powered with TF39 engines made its final flight to Davis-Monthan Air Force Base for retirement. The TF39 was effectively retired, and all remaining active C-5 Galaxies are Rebuilt C-5M Super Galaxies, powered by F138-GE-102 (derivative of

General Electric CF6-80C2 The General Electric CF6, US military designations F103 and F138, is a family of high-bypass turbofan engines produced by GE Aviation. Based on the TF39, the first high-power high-bypass jet engine, the CF6 powers a wide variety of civilian a ...

, specifically for C-5M upgrade) engines.

Development

The

United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

opened the "CX-X Program" in 1964, intending to produce a next-generation strategic

airlifter A military transport aircraft, military cargo aircraft or airlifter is a military-owned transport aircraft used to support military operations by airlifting troops and military equipment. Transport aircraft are crucial to maintaining supply ...

. 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 Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...

by about 25%. The TF39 had an 8:1 bypass ratio, a 25:1 compressor pressure ratio, and 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.

Design

The TF39 was a revolutionary 1960s engine rated from 41,000 to 43,000 lb_f (191 to 205 kN) of thrust. It introduced use of a large by-pass ratio which, together with advances in core technology, contributed to a significant improvement in fuel efficiency over engines available at the time. The engine included features developed from previous GE engines: * Variable

stator The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, mud motors, or biological rotors (such as bacterial flagella or ATP synthase). Energy flows through a stator to or from the rotat ...

vanes (used in the J79/CJ805"seven decades of progress" General Electric, , Aero Publishers Inc. p.152) * Turbine cooling techniques (advanced from the J93 used in the XB-70) * Cascade-type

thrust reverser Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to ...

(from the CJ805) * Snubbered first stage fan blades (snubbers, or mid-span shrouds, had been introduced by GE on the YJ93 first stage compressor blades"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) 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. This aircraft had two X353-5 engines, each consisting of a 62.5-inch-diameter lift-fan driven by a gas generator (J85). The bpr in VTOL operation was 12.3. This tip-turbine driven lift-fan concept was turned 90 degrees and developed as an 80-inch-diameter "cruise fan" demonstrator, driven by a J79 gas generator. 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. This was developed into the TF39 with a 97 in diameter fan. By modern standards the Low Pressure Compressor on the TF-39 is fairly unique as a single T-stage is mounted upstream of the fan rotor, rather than behind it. Although this T-stage supercharges the inner section of the fan rotor, not all of this airstream enters the High Pressure Compressor as a fair proportion also enters the bypass duct to supplement the air discharging from the outer section of the fan. In other words there are three streams leaving the fan, two of which enter the bypass duct.https://aviation.stackexchange.com/questions/51747/why-does-the-cf6-have-a-lower-bypass-ratio-than-the-tf39

Applications

* Lockheed C-5A/B/C Galaxy

Specifications (TF39-1C)

References

External links