Snecma says it continues to pursue engine deals with business jet airframers developing new programmes despite three years without securing a launch customer for its 9,500-12,000lb thrust (42-53kN) Silvercrest turbofan.

A pause in new programmes while the economy improves could serve the Safran subsidiary well as airframers such as Cessna and Dassault re-evaluate projects like Columbus and Future Falcon, respectively, both of which were delayed indefinitely with the downturn.

Dassault had previously picked the Rolls-Royce RB282-3 engine for its Falcon 50EX replacement; Cessna had selected the Pratt & Whitney Canada PW810.

"It's not lost time; it's time to better integrate new requirements from airframers," says Snecma general manager for the business aviation market, Loic Nicolas.

Areas where airframers are looking for more performance include emissions, noise and specific fuel consumption, says Nicolas. Snecma, through its joint venture work with GE on the CFM programme, is investigating lean burn combustor technologies in place for the Leap-X1C and GEnx engines for the airline market.

Nicolas says the company is actively testing modules for other improvements, although he would not elaborate. CFM is investigating a variety of new materials for the Leap X to reduce engine weight and increase durability, including 50/50 titanium-aluminium alloy cast blades for the low-pressure turbine and ceramic matrix composite blades for the core.

While the engine's architecture - four axial and one centrifugal compressor stages - would typically limit such an engine to about 12,000lb thrust, Nicolas says experience in testing the Silvercrest core in 2008 proved otherwise, opening the door to a wider array of potential applications for the engine. "We decided to demonstrate that you can generate much more [thrust]", says Nicolas, although he would not provide a number.

Centrifugal stage limitations were a key element in P&WC's decision to design its PW800 series of turbofans with axial flow compressors, a fundamental change from its next smaller PW300 series engines powering aircraft such as the Dassault 7X. P&WC is in the midst of a six-month core test of the PW800.

"We dropped [the impellor] for several reasons, the first is growth," says PW800 programmes director Dan Breitman. "The second, as you go into higher temperatures and pressure, the thermal gradients across the impellor is an issue."

Snecma's Nicolas acknowledges that the temperatures are higher but says "we have ways to fix it".

Source: Flight International