Pratt & Whitney will continue working on the next generation of geared turbofan engine technology despite its exclusion from the Boeing 777X re-engining competition.
The early success of the PurePower PW1000G series in the narrowbody market masks a key limitation. The 3:1 ratio used by the PW1000G reduction gear is insufficent to power widebody aircraft or a next-generation single-aisle.
P&W is conducting "due diligence" studies on a new reduction gear with an at least 4:1 ratio to power the next generation of its commercial aircraft, says Bob Saia, P&W vice president of next generation engines.
The 25% upgrade ratio applies a change in the architecture of the reduction gear. The PurePower 1000G series employs a five, fixed gears in a star configuration. The next generation will use an all-moving planetary gear to achieve the higher reduction gear ratio, Saia says.
Such a new gear will be inherently more fuel-efficient than current technology.
"That's probably worth something on the order of 5 to 6% better fuel efficiency," Saia says.
P&W did not use such a gear at the outset years ago for several reasons, not least because it was more risky and airlines were already having trouble accepting the reduction gear technology in the first place.
Boeing's plan to introduce the 777X by the end of the decade was too fast for P&W to support with an all-new engine architecture, Saia says.
"We really neeeded to do due diligence on this technology profile," he says.
In addition to the gear, P&W also is working to increase the overall pressure ratio (OPR) inside the core of a next generation engine to 60:1, he says. The existing PurePower architecture features an OPR at 45:1.
(Correction: Story updated to clarify that Pratt & Whitney decided not to submit a final bid for 777X programme.)