Recessions come and go, but the quest to develop ever more efficient engines for the next generation of single-aisle aircraft continues. Given the time it takes to develop new powerplant technologies, which can be measured in decades, engine manufacturers have to be more confident than most of eventual recovery in the airline industry if the millions spent on research and development are not to be wasted.

Despite the continuing slowdown in the air transport sector, all three major larger engine manufacturers–General Electric, Pratt & Whitney and Rolls-Royce–have told AIN that they remain totally committed to developing the next generation of engines which will have to meet ever tougher environmental targets while bringing costs of ownership down through improved reliability.

GE Aviation, for example, spends more than $1 billion a year on research and development, and Mark Pearson, leader of advanced technology, said the company is “keeping its foot hard on the R&D pedal.” While investment has flattened slightly during the recession, “all of our technical programs are on schedules we set two years ago,” he said.

The strategy put in place by GE Aviation president and CEO David Joyce after the 9/11 terrorist attacks remains firmly planted. This was to maintain and, if possible, increase the R&D spend, a policy that has been pursued relentlessly, leaving the company extremely well placed, said Pearson, to face the future with confidence.

“We are at an important juncture in our history,” Joyce said earlier this year. “Over the next 20 years, jet engines will have to perform at greatly improved levels in terms of fuel efficiency, lower emissions, cost of ownership and electric power generation. GE will be at the forefront of these technology breakthroughs because of the hard work and investments under way today.”

At the same time, Pratt & Whitney senior vice president, engineering, Paul Adams admitted that P&W’s overall R&D budget has been cut by around 15 percent this year. However, he added that the company is determined to maintain or even increase investment on the fundamental research needed to develop the next generation of geared turbofan (GTF) engines to which it is committed. “We recognize the GTF is crucial to the future of the company and one of our highest priorities is to get through risk reduction. There is no slippage on technology programs. They are 100 percent funded,” he said.

At last year’s Farnborough International airshow, GE Aviation launched its eCore program for aircraft carrying 200 seats or fewer, with the aim of “dramatically improving efficiency over current engines.” The engine incorporates much of the technology developed for its GEnx engine powering the Boeing 787, as well as some from military engines, such as the F136 for the F-35 Joint Strike Fighter. Ceramic matrix composites, for example, used in the F136 low-pressure turbine nozzle, halve the weight of a typical turbine blade, operate at higher temperatures and do not require cooling, so are easier to manufacture.

The first eCore ran on time in June as part of CFM International’s LEAP-X development program to develop a replacement for the current CFM56 turbofan with 16 percent lower fuel burn. A full demonstrator engine is due to run in 2012. CFM International is GE’s alliance with French engine maker Snecma.

Reliability Questions Challenge Open Rotor
Research into an open-rotor solution to the next generation of single-aisle aircraft remains clouded by reliability worries, said Pearson. “There is a tremendous amount of work to do. We’re still committed to a potential 2018 in-service date if the industry wants it. But there are certification issues. The challenge is to provide at least the same reliability as we get now. Today’s CFM56s give airlines a shop visit rate of six or seven years. We have to do the same with an open rotor and at present we cannot overstate the reliability challenge of a pitch change mechanism [for the contra-rotating open rotor blades] that will give us that figure.”

Noise is also a “tough challenge,” Pearson said, but on an optimistic note, he added that GE Aviation’s experience with the Unducted Fan program in the 1980s “means we’re ahead of the game with respect to our competitors.” He also revealed that the eCore engine cycle “is ideally suited” to the requirement for a core of an open-rotor engine. “The cycle balances out very well,” he said.

GE Aviation is pushing its supply chain as part of the recession-driven effort to reduce manufacturing costs. “It’s just as important as introducing new technology,” Pearson said. A new $100 million manufacturing technology center is to open in Michigan later this year to focus on improving the productivity and competitiveness of manufacturing technologies. “We is to use this extensively to reduce costs,” he added.

The only other major manufacturer to be working on contra-  rotating open-rotor designs is Rolls-Royce, Pratt & Whitney having committed to geared turbofans for all foreseeable civil engine applications. Before last June’s Paris Air Show, Robert Nuttal, vice president, strategic marketing at Rolls-Royce, told AIN there are no engineering show stoppers to development of an open-rotor engine. “We’re a lot more confident it can be done,” he said.

According to Rolls-Royce, there has been “no reduction” in its investment in technology, which is seen as a “vital element of our future position and the options program. We have a very highly structured technology readiness program that gate-checks developments on a regular basis to de-risk technologies.”

The company spent around $1.6 billion on research and development in 2008 and remains fully committed to its Option 15-50 strategy covering development of a range of new engines from the three-shaft RB285 Trent follow-on with a 15-percent lower fuel burn to an open-rotor powerplant. Tests with a counter-rotating open-rotor model between August 2008 and March 2009 confirmed the potential for a 25- to 30-percent improvement, added the company.

Development spending on current programs at Pratt & Whitney has been reduced somewhat following the unexpected suspension of the Cessna Citation Columbus business jet program and the recently announced delay to the Mitsubishi Regional Jet (MRJ). Only the Bombardier C Series application for the PW1000G remains on track, with the first core of the PW1524 engine due to run this winter and the first engine to test in 2010, marking the beginning of full-scale development leading to certification at the end of 2012.

Nonetheless, Adams said he is “still very bullish” about the Mitsubishi program following the company’s decision to go for a more conservative MRJ design. The change from an oval to a circular fuselage section and from a composite to aluminum wing “will mean there is less risk in the program and lower up front costs.”

An Entirely New Class of T-fans
Confidence in the PW1000G program is growing rapidly as test milestones are clocked up.

In August, P&W successfully completed accelerated endurance testing equivalent to more than 20,000 hours of service on the all-important fan drive gear system. More than 1,000 hours of laboratory testing on the system have simulated 40,000 takeoffs at equivalent 30,000 pounds of thrust loads, 15,000 of which were maximum-torque takeoffs at extreme oil temperatures. Inspections revealed the gears, bearings and components to be in “excellent condition,” said Pratt & Whitney.

The PW1000G is now referred to as a first-generation example of what Adams calls “an entirely different class of turbofans.” The U.S. company, working with Pratt & Whitney Canada under the new “one company product” philosophy, has accelerated its effort to develop a second-generation follow-on to power future single-aisle aircraft that is even more fuel efficient.

With a wider diameter fan providing a bypass ratio of up to 18:1, the new GTF could, said Adams, burn 8 to 10 percent less fuel than the current PW1000G series, depending on service entry. This would mean an overall fuel-burn reduction of up to 25 percent compared to the most fuel-efficient versions of the V2500 and CFM56.

The current recession has prompted a renewed effort to improve the efficiency with which fundamental research is carried out, said Adams. Three main areas are being pursued: use the one-company principle to take advantage of the best attributes P&W has available; work more effectively with collaborative partners such as Sweden’s Volvo and Germany’s MTU; and secure more fundamental research contracts with selected universities.

“Historically, we haven’t had long-term links with universities,” said Adams. “But for our future engines we realized we need the best world-class understanding of the technologies available.” Eleven universities in the U.S. and Canada have so far been signed up, including the Ohio State University, which is working on gear and transmission technologies.

The debate on the best approach to powering the future single-aisle aircraft continues to divide the aero-engine industry into two distinct camps: GE Aviation and Rolls-Royce favoring open rotors; Pratt & Whitney, the geared turbofan. While there appears to be some indication that open rotors face an uphill struggle to meet or exceed the stringent reliability and maintenance levels being set by today’s engines, spending on the necessary research continues, despite the recession, and both companies have ad-vanced turbofan fallback options should their open-rotor programs fail to live up to expectations.

For now, only Pratt & Whitney is committed to a configuration for its next-generation engine, and while it will find it hard to meet the claimed fuel-burn advantage of an open-rotor design, the company is certain that its strategy will pay off in terms of market acceptability.