General Electric CF6

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CF6 turbofan at the KLM engine shop

The General Electric TF39 and CF6 are a family of high-bypass turbofan engines. Originally developed to power the C-5 Galaxy, they have gone on to become the most popular large aircraft turbines in the world^{[citation needed]}, powering civil and military widebodies from a variety of manufacturers. They also form the basis for the LM2500, LM5000 and LM6000 marine and power generation 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.

[edit] Variants

[edit] TF39

The TF39 is a revolutionary 1960s engine rated from 191 to 205 kN (41,000 to 43,000 lb_f) 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^[a] 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 of the TF39 (http://www.aircraftenginedesign.com/pictures/TF39.gif). Note the very long gas generator used in this pioneering design.

[edit] CF6-6

An FAA cutaway diagram of the CF6-6 engine

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 (low pressure) turbine, supercharging a 16-stage HP (high pressure) axial compressor driven by a 2-stage HP turbine; the combustor is annular and exhaust separate jets. The 2194,5 mm (86.4 in) diameter fan generates an airflow of 591 kg/s (1303 lb/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 177,9 kN (40,000 lb_f).

A complete disintegration of a CF6-6 fan assembly resulted in the loss of cabin pressurization of National Airlines Flight 27 over New Mexico, USA in 1973.^[1] The failure of a CF6-6 resulted in the Sioux City, Iowa USA crash of United Airlines Flight 232 in 1989.

[edit] CF6-50

The CF6-50 series are high-bypass turbofan engines rated between 205 to 240 kN (46,000 to 54,000 lb_f) 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 two stages from the rear of the HP compressor (even leaving an empty air passage, where the blades and vanes had once been located). two extra booster stages were added to the IP (intermediate pressure) compressor, which increased the overall pressure ratio to 29.3. Although the 2194,5 mm (86.4 in) diameter fan was retained, the airflow was raised to 658 kg/s (1450 lb/s), yielding a static thrust of 227 kN (51,000 lb_f). 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 214 to 334 kN (48,000 to 75,000 lb_f). 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,^{[2] [3] [4]} some which resulted in 767s being written off,^{[5] [6] [7]} 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. ^[8]

The -80 series is divided into three distinct models.

[edit] CF6-80A

The CF6-80A, which has a thrust rating of 214 to 222 kN (48,000 to 50,000 lb_f), 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 2194,5 mm (86.4 in), with an airflow of 651 kg/s (1435 lb/s). Overall pressure ratio is 28.0, with a bypass ratio of 4.66. Static thrust is 214 kN (48,000 lb_f). 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 234 to 282 kN (52,500 to 63,500 lb_f). 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.^{[citation needed]}

For the CF6-80C2-A1, the fan diameter is increased to 2362 mm (93 in), with an airflow of 795 kg/s (1754 lb/s). Overall pressure ratio is 30.4, with a bypass ratio of 5.15. Static thrust is 263 kN (59,000 lb_f). 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, Boeing 767 aircraft and the U.S. Air Force's C-5M Super Galaxy

[edit] CF6-80E1

The CF6-80E1 is specifically designed for the Airbus A330, with thrust rating of 300 to 334 kN (67,500 to 75,000 lb)_f. For the CF6-80E1A2, the fan diameter is increased to 2438 mm (96 in), with an airflow of 873,6 kg/s (1926 lb/s). Overall pressure ratio is 32.6, with a bypass ratio of 5.3.

[edit] Other variants

The industrial and marine development of the CF6-80C2, the LM6000 Series, has found wide use including fast ferry and high speed cargo ship applications, as well as in power generation. Unlike the LM2500 and LM5000, it is capable of cold (compressor) end drive allowing for an axial exhaust which aids power output and efficiency. The LM6000 actually uses the LP compressor section from the CF6-50.

[edit] CF6-32

The CF6-32 was intended to be a stripped-down version of the CF6-80 for the Boeing 757. It was never launched due to lack of interest from airlines.

[edit] Applications

• TF39
  • Lockheed C-5A/B/C Galaxy
• CF6-6
  • McDonnell Douglas DC-10-10
• CF6-50
  • McDonnell Douglas DC-10-30
  • Boeing 747-200/-300
  • Airbus A300
  • McDonnell Douglas KC-10 Extender
  • Boeing E-4B NAOC
• CF6-80
  • Boeing 747-400/-400ER
  • Boeing VC-25 (Air Force One), the only CF6-80 application on 747-200s
  • Boeing 767
    • Boeing E-10 MC2A
    • Boeing E-767 AWACS
    • Boeing KC-767
  • Lockheed C-5M Galaxy
  • McDonnell Douglas MD-11
  • McDonnell Douglas MD-12
  • Airbus A310
  • Airbus A330

[edit] References

[edit] Notes

[edit] External links

• GE CF6 website
• Volvo Aero CF6-80 webpage subcontractor
• NTSB Safety Recommendation on GE CF-6 engines of December 12 2000 PDF 262 KB
• Engine failures cause GE overhaul Cincinnati Post, January 3 2001