CFM Bets on Composites for Advanced Turbofan
Engine maker CFM has chosen sides in the debate between proponents and opponents to composite materials on turbofan moving parts by introducing fibers woven in three dimensions for fan and even low-pressure turbine (LPT) blades. The bet on this next-generation composite manifests itself on the Snecma-General Electric venture's Leap-X “advanced turbofan” program.
Moving from metal to 3D-woven composite fan blades and case will save 1,000 pounds on a twin-engine aircraft, says CFM. The partners also plan to demonstrate that the detachment of the inner part of the blade is so unlikely that blade-off tests need only be conducted with the outer half. On the LPT, a ceramic-matrix composite material saves 340 pounds per aircraft.
GE already uses composite blades (albeit two-dimension woven) on the GE90, which powers the Boeing 777. Rolls-Royce, meanwhile, is sticking to titanium for fan blades on its latest programs. CFM’s composite fan blades still retain a titanium leading edge.
In positioning the Leap-X as a successor to the ubiquitous CFM56 engine on narrowbody airliners, Snecma and GE feel little pressure to speed development because Airbus and Boeing now don’t plan to replace the A320 and 737 until late next decade or even 2020. Moreover, CFM engineers have consistently shrugged off the threat posed by Pratt & Whitney's geared PW1000G. Consequently, the Leap-X’s development schedule looks almost relaxed, with targets for a full engine demonstration in 2012 and certification by 2016. At last, Snecma and GE appear to have learned a hard lesson from major delays in programs such as the TP400 military turboprop engine.