CFM International has thrown down the gauntlet to engine manufacturers hoping to compete on the next generation of single-aisle airliners by accelerating its research on an advanced engine to replace its CFM56 by as early as 2015, the company announced here yesterday.

The GE Aviation/Snecma partnership has extended its Leap56 technology acquisition program to include open rotor and contrarotating fan configurations as well as a conventional turbofan. “We’re facing a tremendous challenge,” said Leap56 director Ron Klapproth. “We’ve talked to more than 30 airlines about the next-generation engine. They’re saying a 20-percent aircraft-plus-engine fuel burn gain isn’t enough. They would like to see a step change to maybe 30 percent.”

CFM plans to undertake the initiative outside the recently launched European Union Clean Sky program, which runs to 2014 and involves Snecma and other European manufacturers in developing up to five advanced engine demonstrators.  “We want to make a decision on architecture by 2011-2012,” says Klapproth. “Depending on the results of Leap56 we would then make a decision on whether to recommend a conventional turbofan for 2015 or an open rotor design for later in the decade.”

CFM plans to explore open rotors “to their fullest extent,” and has already recovered raw data from GE’s early 1980s Unducted Fan open rotor program. “We’ve run dozens of configurations and scale models during the last six months using the latest aerodynamic codes,” said Klapproth. “The results told us there are opportunities for efficiency and acoustics improvements.”

To date, the Leap56 program has concentrated on an advanced conventional successor to the CFM56, which would yield a 15-percent fuel burn improvement and be at least 10dB quieter than today’s engines, while bringing a 60 percent reduction in oxides of nitrogen and a 15-percent cut in maintenance costs. Klapproth said that if other approaches fail, the airlines will be offered a conventional turbofan based on this technology. “But we’re putting the other engine program in place to see if we can deliver an open rotor engine by the end of the decade.”

CFM has ruled out the geared turbofan approach taken by Pratt & Whitney. “We’ve done a lot of studies recently. The fact is we can deliver the same fuel burn and acoustics as the GTF with the Leap56. The GTF isn’t a game changer. The open rotor is.”