General Electric TF39

The General Electric TF39 is a high-bypass turbofan engine that was developed to power the Lockheed C-5 Galaxy. It was the first high-bypass jet engine developed.

TF39
A TF39 on a C-5 Galaxy at ILA (Internationale LuftfahrtAusstellung) in Berlin, 2008
Type	High-bypass turbofan
National origin	United States
Manufacturer	GE Aviation
First run	1964
Major applications	Lockheed C-5 Galaxy
Number built	463
Developed into	General Electric CF6 General Electric LM2500

Development

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 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.^[1] This aircraft had two X353-5 engines, each consisting of a 62.5-inch-diameter^[2] lift-fan driven by a gas generator (J85). The bpr in VTOL operation was 12.3.^[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.^[1] 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.^[4] This was developed into the TF39 with a 97 in diameter fan.

The high-bypass substantially improved the thrust and fuel consumption compared to the previous GE jetliner turbofan, the CJ805-21.^[1] It had two and a half times the thrust, while improving fuel efficiency by about 25%.^[5] 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.

The TF39 core was used for the CF6 series of engines, and the LM2500 and LM6000 marine and industrial gas turbines.

Design

TF39s on a C-5 Galaxy, from the rear

TF-39 on display at the Museum of Aviation View looking into the fan showing snubbered blades on the inner half-stage and inlet guide vanes in the outer duct in front of the full stage.

The TF39 produced 41,000 to 43,000 lb (191 to 205 kN) of thrust. It 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 the latest cooling technology.

The engine included features developed from previous GE engines:

• Variable stator vanes (used in the J79/CJ805^[1])
• Turbine cooling techniques (more advanced than used on the YJ93^[1])
• Cascade-type thrust reverser (from the CJ805^[1])
• Snubbered first stage fan blades (snubbers, or mid-span shrouds, had been introduced by GE on the YJ93 first stage compressor blades^[6])

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.^[7]

Operational history

On September 7, 2017, the last C-5A powered with TF39 engines made its final flight to Davis-Monthan Air Force Base for retirement.^[8][9] The only application for the TF39, the Galaxy military transport, was re-engined with the more modern F138-GE-102, a military version of the General Electric CF6-80C2. Re-engining for the whole fleet took place from 2008 to 2018.

Applications

• Lockheed C-5A/B/C Galaxy

Specifications (TF39-1C)

A Boeing B-52E (Serial Number 57-0119) testing a TF39 on the right inboard engine pylon. The TF39 has more than double the thrust of the two Pratt & Whitney J57s that were normally on all four pylons.

Data from ^[10]

General characteristics

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

Components

• Compressor: Axial, low pressure compressor, comprising single stage booster and a single stage fan, 16-stage high-pressure compressor
• Combustors: Annular
• Turbine: Axial, 2-stage high-pressure turbine, 6-stage low-pressure turbine

Performance

• Maximum thrust: 43,300 lbf (193 kN)
• Overall pressure ratio: 25:1
• Fuel consumption: ~3.7646 lb/s (1.7075 kg/s)
• Specific fuel consumption: 0.313 lb/(lbf⋅h) (8.9 g/(kN⋅s))
• Thrust-to-weight ratio: 5.4

See also

Related development

• General Electric CF6
• General Electric LM2500

Comparable engines

• Pratt & Whitney JT9D
• Progress D-18T
• Rolls-Royce RB211

Related lists

• List of aircraft engines