EBACE 2008: The main thrust?

The magic number for engines right now seems to be 10k. But with so many competitors - and currently only one airframe - how viable is this market? Phil Nasskau and Geoff Thomas report on Snecma’s Silvercrest.

Arguably Snecma is set to be the first company with a complete engine, even though it did lose out to Rolls-Royce on the Dassault Falcon SMS competition. But why is Snecma investing $100 million on an engine that so far has no customer?

The Silvercrest engine is designed to produce between 8,000lb and 12,000lb of thrust, though the likely launch thrust will be 9,000/9,500lb, targeting the next generation of large-cabin business jets as well as 40-60-seat regional jets.

The Silvercrest programme now has real performance figures to take to an OEM’s table. In March the core demonstrator test programme was completed, including running at full take-off power (20,300rpm); exhaust gas analysis; transient accelerations; bleed scheduling; and combustion characteristics. The engine had a dedicated test cell at Snecma’s Villaroche site, which was supplied with pressurised intake air at various temperatures and pressures to simulate the new engine’s missing low-pressure fan section.

Speaking in Paris just before EBACE, Snecma’s new VP & GM commercial engine division, François Planaud said the tests confirmed the original choice of architecture as well as validating the various high pressure ‘hot’ sections of the Silvercrest engine.

silvercrest core test

“The core demonstrator ran for around 80 hours, including 62h in combustion mode. I’m pleased to say that we had no unexpected events whatsoever and there were no major corrections to make, just normal adjustments. Through real-time telemetry, we measured around 600 parameters including efficiency, performance, clearances, pressures and temperatures and found all of them at - or even better than - the original design objectives,” said Planaud, who took over the reins from Jean-Pierre Cojan after he moved to become chairman and CEO of Safran Group sister company Aircelle last November.

Although Silvercrest could still be configured as ‘all electric’ or ‘bleed air’, the latter is the baseline choice despite the trend towards non-pneumatic in commercial aviation – witness the much-delayed Boeing 787 Dreamliner.

Laurence Finet, general manager for the programme says: “We have only developed the engine core because we already know how to develop good low pressure systems. We’ve been working on those for 30 years; every CFM engine type has a different low-pressure spool but a common core. That’s not an issue for us. The testing we’ve done is to validate our high-pressure core and its associated modules.”

Presently Silvercrest comprises four HP stages with blisks; a low emission combustor; and a single stage HP turbine. Snecma has used the group’s expertise and the core features a Turbomeca-designed impeller,negating the need for two compressor stages; a four-stage axial-flow compressor; and single-stage high-pressure turbine downstream of the Avio-sourced combustor. The combustor is cross-developed, using technology from both the SAM146 and TP400.

Planaud says that by developing the engine now so Snecma will not need a long lead time. “We’ll be ready when the airframers are ready to go to the next step. We’re targeting certification in Q4 2011/Q12012, with an EIS date of 2013, assuming that we have a launch customer by our target date of early in 2009,” he says.

“We learned a lot from the Dassault competition. It was our first venture into business aviation. It’s a completely new aspect and we are more than ready for the next campaigns. We made it to the final stages of the Dassault competition, and there were a lot of lessons to learn. The next ones will be more successful for us.”

According to Planaud, Snecma (as Silvercrest) is talking to “several” airframers, mostly on the western side of the Atlantic. “The engine is giving us great confidence to go and talk seriously to them and we are ready to launch a full-scale development engine. Maybe 20 or 30 years ago we would have gone ahead and built it – but these days the airframe and engines need to be fully integrated (nacelles and systems) and we are really concentrating on obtaining that launch customer by early next year.”

Loïc Nicolas, Snecma’s general manager, business aviation market, says: “The OEMs face tough competition for their current products, and they are certainly asking us what we can do for them. We are not offering just an engine but a complete propulsion solution with all the support the market expects.”

Nicolas says that Snecma would offer customers both options of either ‘power by the hour’ or ‘time on wing’. The company has the ability to provide real time monitoring for the engine and with no inspections due between major overhauls other than routine boroscope inspections.

Potential airframes for the Silvercrest are there. Embraer revealed concepts last year that may well be suitable. And Snecma certainly likens itself to Embraer in the way that it too developed a strong commercial portfolio before entering business aviation. With the Bombardier Learjet NXT and Cessna LCC ruled out because their power requirements were too low, thoughts have turned towards the larger Bombardier M127 concept. “Much below 9,500lb the engine would not be optimised in terms of weight and fuel burn,” says Nicolas.

According to Snecma’s own market survey there is a demand for 2,600 10k-powered aircraft from 2007 through 2017. The company is hopeful that with long-term growth continuing, especially in emerging markets like Brazil, Russia, India and China, the predicted demand will materialise.