General Electric CF6

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CF6 turbofan at the KLM engine shop

The General Electric TF39 and CF6 family of high-bypass turbofan engines are the most popular large aircraft turbines in the world, powering civil and military widebodies from a variety of manufacturers. They also form the basis for the LM2500, LM5000 and LM6000 marine turboshafts. The family is produced by GE-Aviation, formerly General Electric Aircraft Engines.

General Electric intends to replace the CF6 family with the GEnx, which will have an entry into service date of 2008.

1 Variants
2 Applications
3 References

[edit] Variants

[edit] TF39

The TF39 is a revolutionary 1960s engine rated from 41,000 to 43,000lb_f (191 to 205 kN) of thrust. It is the world's first high-bypass turbofan engine and the parent of the successful CF6 series. It employed a great deal of then-new technological features such as:

1½ stage fan blades (unique to TF39).
8:1 bypass ratio.
Variable stator vanes.
Turbines equipped with advanced cooling.
Fuel efficiency better than any engines available at the time.
Cascade-type thrust reversers.

Since its introduction on the Lockheed C-5 Galaxy military transport, the TF39 has benefited directly from CF6 design technology: components, materials, processes, manufacturing techniques, and repair processes.

Mechanically, the TF39 is rather unusual for a high bypass ratio turbofan; the single stage snubbered fan rotor has a set of inlet guide vanes for the outer bypass section and the core booster stage is located in front of the fan rotor, rather than behind. The following sectional view shows the fan arrangement (http://www.aircraftenginedesign.com/pictures/TF39.gif). Note the very long gas generator used in this pioneering design.

[edit] CF6-6

The CF6-6 was a development of the military TF39. It was first utilized on the McDonnell Douglas DC-10-10.

This initial version of the CF6 comprises a single stage fan, with one core booster stage, driven by a 5-stage LP turbine, supercharging a 16-stage HP compressor driven by a 2-stage HP turbine; the combustor is annular and exhaust separate jets. The 86.4in diameter fan generates an airflow 1303lb/s, resulting in a relatively high bypass ratio of 5.72. The overall pressure ratio of the compression system is 24.3. At Maximum Take-off, the engine develops a static thrust of 40000lbf.

The failure of a CF6-6 resulted in the crash of United Airlines Flight 232

[edit] CF6-50

The CF6-50 series are high-bypass turbofan engines rated between 46,000 to 54,000 lb_f (205 to 240 kN) of thrust. The CF6-50 was developed into the LM2500 industrial and marine turboshaft engines. It was launched in 1969 to power the long range McDonnell Douglas DC-10-30, and was derived from the earlier CF6-6.

Presumably, because a significant increase in thrust, and therefore core power, was required, not long after the -6 had entered service, General Electric could not increase (HP) turbine rotor inlet temperature significantly, so they took the very expensive decision to reconfigure the CF6 core to increase its basic size. They achieved this by removing 2 stages from the rear of the HP compressor (even leaving an empty air passage, where the blades and vanes had once been located). 2 extra booster stages were added to the IP compressor, which increased the overall pressure ratio to 29.3. Although the 86.4in diameter fan was retained, the airflow was raised to 1450lb/s, yielding a static thrust of 51000lbf. The increase in core size and overall pressure ratio, significantly raised the core flow, resulting in a decrease in bypass ratio to 4.26.

In late 1969, the CF6-50 was selected to power the then new Airbus A300. Air France became the launch customer for the A300 by ordering six aircraft in 1971. In 1975, KLM was the first airline to order the Boeing 747 powered by the CF6-50. This led further developments to the CF6 family such as the CF6-80.

[edit] CF6-80

The CF6-80 series are high-bypass turbofan engines with a thrust range of 48,000 to 75,000 lb_f (214 to 334 kN). It is an advanced development of the earlier successful CF6-50 series engine, but despite superficial resemblance, it is a completely new engine with no interchangeable parts. Although the HP compressor still has 14 stages, GE did take the opportunity to tidy-up the design, by removing the empty air passage at compressor exit.

Following a series of high-pressure turbine failures, one of which resulted in a 767 being written off, the FAA has issued an airworthiness directive mandating inspections for over 600 engines. The NTSB feels this number should be increased to include all -80 series engines with more than 3000 cycles since new or since last inspection. ^[1]

The -80 series is divided into three distinct models.

[edit] CF6-80A

The CF6-80A, which has a thrust rating of 48,000 to 50,000 lb_f (214 to 222 kN), powered two twinjets, the Boeing 767 and Airbus A310. The GE-powered 767 entered airline service in 1982, and the GE powered A310 in early 1983. It is rated for ETOPS operations.

For the CF6-80A/A1, the fan diameter remains at 86.4in, with an airflow of 1435lb/s. Overall pressure ratio is 28.0, with a bypass ratio of 4.66. Static thrust is 48000lbf. The basic mechanical configuration is the same as the -50 series

[edit] CF6-80C2

The CF6-80C2, which entered revenue service in October 1985, has a thrust rating of 52,500 to 63,500 lb_f (234 to 282 kN). It has a reputation of good fuel economy in its thrust class. The CF6-80C2 is certified with 16 different thrust ratings. This versatile engine has the most widespread use of any large turbofan engine.

For the CF6-80C2-A1, the fan diameter is increased to 93in, with an airflow of 1754lb/s. Overall pressure ratio is 30.4, with a bypass ratio of 5.15. Static thrust is 59000lbf. A 4th stage is added to the IP compressor and a 5th to the LP turbine.

The CF6-80C2 is currently certified on eleven wide-body aircraft models including the Boeing 747 and McDonnell Douglas MD-11. The CF6-80C2 is also certified for ETOPS-180 for the A300, A310, and Boeing 767 aircraft.

[edit] CF6-80E1

The CF6-80E1 is specifically designed for the Airbus A330, with thrust rating of 67,500 to 75,000 lb_f (300 to 334 kN).

For the CF6-80E1A2, the fan diameter is increased to 96in, with an airflow of 1926lb/s. Overall pressure ratio is 32.6, with a bypass ratio of 5.3.

[edit] Other variants

The industrial and marine development of the CF6-80, the LM6000 Series, has found wide use including fast ferry and high speed cargo ship applications.