Source: Aviationnow.com

Pratt & Whitney's Geared Turbofan Moves Closer To Launch With Mitsubishi RJ Selection

By Guy Norris

Pratt & Whitney is starting detailed design work on the first production version of its geared turbofan family after a pivotal victory in the engine selection competition for Mitsubishi’s new regional jet project.

The win gives Pratt a much-needed breakthrough for its geared turbofan (GTF) product development strategy, which is gambling on industry acceptance of geared-fan technology for a broad range of fuel-efficient engines derived from a new common core. The family is designed to cover thrust requirements from high-end business jets and regional airliners, to next-generation single-aisle transports and beyond. Pratt believes the inherent efficiency of a gear-driven fan will give 12% fuel savings over current engines, with a further 5-7% improvement available by 2020.

The company also overcame bids from General Electric and Rolls-Royce to secure its place on the Mitsubishi Regional Jet (MRJ). GE was offering an advanced development based on the CF34-10, while Rolls was pushing a scaled-up version of the twin-spool RB.282 core architecture recently selected by Dassault Aviation for its super-midsize (SMS) business jet.

Although all three engine manufacturers have close links with their Japanese counterparts—Ishikawajima Harima, Kawasaki and Mitsubishi—the Pratt & Whitney win is also fueling speculation that the MRJ decision could have strategic implications for teaming arrangements on future Airbus A320 and Boeing 737 single-aisle replacement engines.

“It’s an important win, not only because we have a credible program, but also because we have a launch application,” says Todd Kallman, president of Pratt & Whitney Commercial Engines. However, the selection does not yet guarantee the full launch of the production GTF, a demonstrator version of which is poised to begin ground tests at Pratt’s West Palm Beach, Fla., site as early as the end of November. Mitsubishi has board approval to offer the MRJ, and aims to formally launch the airliner in the first quarter of 2008 for entry into service in 2013. The final commitment to start full engine development depends on Mitsubishi securing launch orders for firm launch next year. For now, however, Pratt is “completing optimization and design work for fitting the GTF to the MRJ,” says Tom Pelland, director of Pratt’s Next-Generation Product Family. First engine to test for the 70-90-seat MRJ—which requires a 17,000-lb.-thrust engine for the larger model and a derated 15,000-lb.-thrust version for the 70-seater—will be in 2009, says Pelland.

Although technical details of the GTF configuration for the regional jet application remain sketchy, Pratt is expected to be designing it around the eight-stage high-pressure (HP) compressor and two-stage HP turbine being rig tested at MTU. (MTU is also a partner with Avio and Volvo in the GTF demonstrator phase.) New design features of the eight-stage unit include cantilevered stators, which are attached only on the case side of the blades instead of being “hard” attached to both the case and shaft sides.

To more closely match the optimum operating speed of the HP spool, the three-stage low-pressure (LP) compressor in the GTF is designed to run at almost three times the speed of a conventional LP shaft. In addition, all three stages are fitted with variable guide vanes, though rig tests at Pratt are underway to see if at least one stage of these can be eliminated. It’s not yet known, therefore, if the selected MRJ configuration is outlined with two- or three-stage LP compressor and turbine sections.

The importance of the Mitsubishi win to Pratt’s long-term future beyond the regional market is also evident, according to the company’s president, Steve Finger. “It’s clear we have lost market share in the new-engine commercial marketplace on the large commercial engines. We believe this is the step back to a stronger position. It’s something we’ve been working on for almost 20 years.”

The call is echoed by United Technologies President and Chief Operating Officer Louis Chenevert, a long-standing advocate of the GTF. Speaking prior to the MRJ announcement, Chenevert says “we have a lot of airlines that have piled in behind Pratt to say, ‘We support the GTF, we want to see it come to life sooner rather than later.’ What we need at this point is an OEM [original equipment manufacturer] to launch the GTF technology.”

Finger believes soaring fuel prices are helping ignite the kind of interest in the GTF concept shown by Mitsubishi. “This is the answer. This is the game changer. . . . You can incrementally improve the engines you have, but that will fall significantly short in fuel burn and economics. Or you can wait and hope there’s going to be something better in 10 or 15 years.”

According to Finger, GTF would save $1.5 million annually per aircraft on a single-aisle transport (using two GTFs) over today’s existing engines. That’s savings from fuel, maintenance (lower cost because of fewer parts) and reduced noise fees, and possible emissions benefits. “That’s a lot of money. For the whole industry that would be like $10 billion. You could double the industry’s profit.”

Although alternative open-rotor concepts have been discussed by GE, Rolls and Snecma, Pratt is sticking to its geared option as being the preferred, and nearest-term, solution. Having spent around $1 billion on the development to-date, and currently spending at the rate of approximately $100 million per year, the company also recently revealed a spiral upgrade plan designed to keep it competitive with open-rotor designs to 2020 and beyond (AW&ST Aug. 13, p. 50).

Finger adds that a “25,000-lb.-thrust geared turbofan engine is 8 ft. in diameter. A 25,000-lb.-thrust open rotor engine is 14-17 ft. in diameter, depending on whether it’s a counterrotating twin prop or a single prop. . . . Our analysis says the installation impact and the extra weight that goes with that more than offsets the fuel-burn benefit. So there’s no net burn fuel benefit from an open rotor. There is a noise detriment from the open rotor. And there is a reliability detriment because of the variable-pitch mechanism. You put all that together, and we think open rotors are unlikely to be a solution in the future. Even if they are, they would be way out in the future. We have the answer here in a geared turbofan by 2013.”

Commenting on the engine selection, Mitsubishi President Kazuo Tsukuda says “we believe the [GTF] offers a technological breakthrough that will provide the best economy and performance for the Mitsubishi Regional Jet.” He adds, “We believe by realizing the MRJ project we can help boost the civil airplane industry to become one of the country’s key industries.” The company has ambitions to sell up to 1,000 MRJs over the next 20-plus years, taking at least one-fifth of the predicted regional jet market currently dominated by Bombardier Aerospace and Embraer. Mitsubishi also says it plans to invest about ¥150-billion ($1.28-billion) on the project.

The investment community is also sitting up and paying attention to Pratt’s GTF success with the Japanese project. Morgan Stanley Research analyst Heidi Wood calls the MRJ selection a “key win and an important first step. It’s been clear to gain credibility, P&W’s new-generation Geared Turbo [GTF] engine needed to find an airplane. Pratt’s sole-source selection on Mitsubishi’s regional jet is not a huge surprise, but is an important win in itself, plus a critical foot in the door to winning a position on the next-generation, single-aisle replacement from Boeing and Airbus in the next decade.”

With Bombardier’s CSeries next in-line to make an engine selection around year-end, all eyes will be on this contest. “Another Pratt GTF win would buttress its positioning, proving out technology Rolls and GE have been dismissing. Critically important will be Pratt’s success in demonstrating how GTF technology produces 12% fuel efficiency and 20-25-dB. noise reduction without the higher maintenance costs expected with added gearing,” says Wood.

Credit Suisse also sees other strong changes for Pratt and the GTF. “We believe the GTF is well positioned, as management clearly expressed the need for significant improvement over current technology to make the aircraft attractive to potential customers.”

With Joseph C. Anselmo and Anthony L. Velocci, Jr., in Hartford, Conn.

TOP