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 airliners. The basic engine core also powers the LM2500 and LM6000 marine and power generation turboshafts. It is gradually being replaced by the newer GEnx family. Development After developing the TF39 for the C-5 Galaxy in the late 1960s, GE offered a more powerful variant for civilian use, the CF6, and quickly found interest in two designs being offered for a recent Eastern Airlines contract, the Lockheed L-1011 and the McDonnell Douglas DC-10. Lockheed eventually selected the Rolls-Royce RB211, but the latter stuck with the CF6 and entered service in 1971. It was also selected for versions of the Boeing 747. Since then, the CF6 has powered versions of the Airbus A300, A310 and A330, Boeing 767, and McDonnell Douglas MD-11. The high bypass of the CF6 represented a historic breakthrough in fuel efficiency. By 2018, GE has delivered more than 8,300 CF6s: 480 -6s, 2,200 -50s, 4,400 -80C2s, more than 730 -80E; and 3,000 LM6000 industrial and marine derivatives. The in-service fleet include 3,400 engines, more than all the GE90s and GEnx, generating over 600 shop visits per year. GE will be delivering engines well into the 2020s and they will fly for 20 to 25 years, until 2045-50: more than 75 years since the first CF6. As express delivery spurs an air cargo resurgence, Boeing plans to increase the CF6-80C2-powered 767 E-767 KC-767 delivery rate from 2.5 to 3 per month in 2020, a type introduced in 1982. As CF6-80E1s are still delivered for the Airbus A330 and Airbus A330 MRTT, CF6 production will grow from 50 to 60-80 per year by 2020. GE also studies reengining the Progress D-18-powered Antonov An-124 freighters with CargoLogicAir, a Volga-Dnepr subsidiary. This would likely provide a range increase, and Volga-Dnepr Group operates 12 aircraft, implying a 50-60 engines with spares program. Variants CF6-6 The CF6-6 was a development of the military TF39. It was first used on the McDonnell Douglas DC-10-10. This initial version of the CF6 has a single-stage fan with one core booster stage, driven by a 5-stage LP (low pressure) turbine, turbocharging a 16-stage HP (high pressure) axial compressor driven by a 2-stage HP turbine; the combustor is annular;