"GE Aircraft Engines spends billions of dollars to get a point of efficiency [from an engine]," says Steve Walters, president of Nexcelle, a new integrated propulsion system joint venture between GE and Safran. "For pretty nominal non-recurring costs for the development of an IPS, you can get multiple points of fuel efficiency."

DESIGN ACTIVITIES

Major engine manufacturers and their joint ventures are immersed in integrated propulsion system design activities to compete in the most effective way for a handful of new or updated ultra

Among them, Rolls-Royce is studying integrated propulsion as part of its Option 15-50 project for the next-generation single-aisle aircraft, while P&W is investigating options through its parent company United Technologies' propulsion systems integration centre, a laboratory created five years ago to model the systems integration aspects of UTC's contributions to theBoeing 787.

However, GE and Safran appear to be placing the largest bet by launching the Nexcelle partnership in June. It is modelled on CFM International, the Franco-US 50/50 partnership between GE and Snecma that has produced the most prolific engine in commercial aviation history, the 18,500-34,000lb-thrust (82-150kN)CFM56family.

Nexcelle combines the experience of GE's Middle River Aircraft Systems (MRAS) group, provider of aerostructures and nacelles for several GE engine models - including nacelles for theCF34-10A engine for China'sARJ21regional jet and thrust reversers for theGEnx-2B engine for theBoeing 747-8- with Snecma's Aircelle subsidiary, which builds the nacelles for most of the Airbus family aircraft and several business jets.

Many core competencies of the two companies overlap, but each has specialities - MRAS with electric nacelle components and Aircelle with an electrical thrust reverser for theA380- that will bring a holism to the team. The companies can also reach back into the core competencies of their parents, both of which will have access to the intellectual property developed in the partnership, some of which may also be used for business jet applications.

Nacelles typically include the engine inlet, fan cowl, thrust reverser and associated equipment, plumbing, wiring and electronics.

Bidding wars are likely to begin fairly soon, fuelled by the demanding performance requirements of an atypical entrant - the Commercial Aircraft Company of China (Comac) with its 130- to 200-passenger single-aisleComac 919 twinjet.

The 919 is set for a first flight in 2014 and service entry in 2016. MRAS officials say the Comac integrated propulsion system will "push the state of the art", including electric anti-ice protection for engine inlets rather than the traditional hot bleed air, and an electrical thrust reverser activation system (ETRAS), an advanced technology that debuted on the A380, as well as other new features.

In a related development, China's AVIC and Nexcelle agreed on 23 September to explore a newjoint ventureto "consider a broad range of nacelle and components manufacturing and design opportunities" for current production aircraft and new designs ranging from "business jets to large airliners".

Integrated propulsion system requests coming on the heels of the 919 will includeEmbraer's KC-390 tanker transport, to be powered by two 27,000lb-thrust turbofan engines. First prototypes are due to fly in 2015. Integrated propulsion systems will also be included in some form if there is to be a re-engining of the Airbus and Boeing single-aisle fleets around mid-decade because of the further slipping of next-generation single-aisles to post-2020.

Nexcelle's technology roadmap gives a glimpse of how much there remains to optimise on today's commercial airliners. The effort is designed to mature all required technologies to be able to build a prototype nacelle and pylon to be mated with a "Leap X"CFM56turbofan engine for a full-scale test by the end of 2012, says Eric Masse, vice-president of engineering for Aircelle.

"We have started to work all these demonstrations to make sure we can meet a TRL 6 [technology readiness level of a prototype] to make sure we can meet the requirements of OEMs," he says, cautioning that it is not clear when the OEMs will "push the button" for a new product.

Leap Xis CFM's advanced technology programme to build a next-generation turbofan with 16% less fuel burn for the engine alone, compared with today's CFM56s. The company is promising additional savings if the engine is matched to the airframe and systems using its integrated propulsion system concepts.

Nexcelle is investigating more than a dozen new technologies to decrease fuel burn, noise and maintenance, while increasing the reliability of the integrated propulsion system. As well as increasing the use of electric actuation rather than hydraulic or pneumatic, engineers are moving toward weight-saving and maintenance-friendly monolithic structures, improved acoustics and a variety of design tools to better harmonise the wing, pylon, nacelle and engine combination.

Key projects for the joint venture include developing a one-piece "O" duct for the thrust reverser, which eliminates weight and complexity compared with today's two-piece ducts; designing an electric engine inlet heater that is embedded in the composite material used to form the inlet; and reducing generator requirements, hence fuel burn, by optimally managing power needs for the fan nozzle control, engine inlet anti-ice, ETRAS and other systems according to the phase of flight.

Norton DePinho, marketing and strategy leader for GE Aviation Mechanical Systems, says the move to resistive heating elements woven into the composite engine inlet will eliminate the double-ducted tubing going forward from the engine to the inlet as well as the air duct system for anti-ice protection.

DePinho says the new system will also eliminate the burst-duct potential from high-pressure bleed air. MRAS has already successfully tested the technology, he adds.

Engineers are also developing acoustic treatments to reduce the integrated propulsion system noise to as much as 15dB below Stage 4 standards, says Aircelle's Masse. "The A380 is state of the art, but we are developing, in partnership with engine manufacturers, new technologies for even greater noise reductions."

-fuel-efficient aircraft models being pondered or pursued byAirbus,Boeing and others.