Aircraft

CFM International sees noise mitigation as one of the major technical challenges to be overcome for open rotor to become viable, alongside airframe configuration and meeting certification requirements.

"There are a lot of targets to be passed, like the noise impact, the installation impact for the aircraft, and the maintenance," says CFM executive vice-president Olivier Savin.

The General Electric/Snecma joint venture is using its already-launched Leap-X advanced turbofan programme to provide "foundational" technologies for a potential open rotor architecture, which was unveiled at the 2008 Farnborough International air show.

© CFM International

The company believes that "breakthrough" aerodynamics and materials technologies will be required to minimise weight and improve component efficiency sufficiently for the large-diameter open rotor concept to be viable.

CFM says there is some "dedicated technology development and maturation going on" for its open rotor concept, which could be readied for service entry "a couple of years" after the Leap-X enters airline service in 2016 or beyond.

"We need to keep all options open," says Savin. "It's very attractive to imagine such a new architecture because you can easily reach a 26% lower fuel burn versus the current CFM56, so CFM is working to check whether it's achievable in the coming years.

"All the research performed by CFM for the Leap-X advanced turbofan will be very useful inside this engine, regarding the design, materials and technology.

"Of course it will be a big challenge for us to demonstrate that such an architecture is achievable and feasible. The main aspect of our strategy is to keep all alternatives open with the different partners that we are working with."