While calling extending its geared turbofan engine family’s thrust rating by another 2,000 pounds “a big deal,” Pratt & Whitney next-generation product family vice president Bob Saia sees still bigger things in the company’s future, including what he called an Advanced GTF that could rival an open-rotor design in fuel efficiency by the middle of the next decade. For now, though, Saia finds himself “busy as a bee” with the five core programs already under way at the U.S. company.
Having received certification for the engine that now powers the Bombardier CSeries flight-test vehicles, Pratt & Whitney (Outdoor Exhibits 3 and 4) expects its second GTF–the PW1100G–to win approval during the fourth quarter to power the Airbus A320neo. While meeting with AIN during a recent press event at Pratt & Whitney’s headquarters in East Hartford, Connecticut, Saia described the extent to which the PW1100G has benefited from “learnings” gleaned from the CSeries powerplant.
“I’d say the CSeries engine did the heavy lifting because it did the initial testing to validate the design,” said Saia, who noted that the first engine to be tested operated at roughly a 1.5-percent performance deficit, compared to 2 to 3 percent in a typical program. The first Neo engine, he explained, ran well within 1 percent of performance guarantees. “The quality of the first 1100G that went to test was probably more like the fifth or sixth engine from the CSeries because it already had all that learning,” said Saia.
Even the CSeries engine required no major redesigns ascribed to technology failings, meaning by the time Pratt had delivered the first two Neo engines to Airbus it had used virtually none of the performance “margin” it allowed itself at the start of the program. As a result, it could increase thrust in the Airbus A321neo’s standard PW1133G by 2,000 pounds without the need for any hardware or design changes.
“We’ve been able to hit all our technical metrics and we’ve been able to use some of the additional development margin to add customer value where needed,” explained Pratt & Whitney vice president of engineering Tom Prete. “The engine will be certified with all the existing redlines, all the existing parameters at the higher thrust level.”
By late May, having built 35 of what it now calls the PurePower engine family, Pratt paid particularly close attention to the concepts of scale and reuse–meaning, for example, the engines designed for the Mitsubishi MRJ closely resemble those destined for the Embraer E175-E2. Similarly, apart from differences in installation elements such as air conditioning and electrical and hydraulic power supply, the CSeries engine virtually replicates the engine under development for the E190-E2 and E195-E2.
Meanwhile, with the engine used for the Bombardier CSeries, explained Prete, the company did “a large amount of scaling” to arrive at the design for the A320neo. In turn, the engine in development for the Irkut MC-21 represents a “reuse” of the PW1100 designed for the Neo.
Maintaining commonality in design between the various engine types mitigates risk on several levels. For example, if the MC-21 program stumbles, Pratt could divert hardware making its way through the supply chain to the Neo program. Scheduled to start building the first engine for the MC-21 later this year and take it to testing by early next year, Pratt also expects to use much of the data collected from tests on the Neo engine to help certify the engine for the Russian airplane.
One big difference in the MC-21 powerplant involves the nacelle system, which will come from Short Brothers in Northern Ireland rather than UTC Aerospace Systems (UTAS). Participating in all four of the other GTF applications, UTAS decided to opt out of the MC-21 program due to manufacturing capacity constraints, said Saia.
Constrained for wholly different reasons, the engine for the Mitsubishi MRJ program became the second GTF family member to fly, back in April 2012. More than two years later, however, the PW1200G has managed to proceed to just beyond the halfway point of its certification program because of three separate delays suffered by the MRJ.
“We like to have the engine program run in cadence with the aircraft program,” said Saia. “There are a couple of reasons for that. One is…how the engine provides air to the air-conditioning system, [and another is] how the engine talks to the cockpit from an electronics perspective…[both] can change as the aircraft is being developed. So if we go too far ahead, what we do is create a system architecture…that may have to be redesigned when you have to put it on the aircraft.”
Saia described Pratt’s running of the first four engines as “really heavy,” through critical testing for stress, structural measurements, temperatures and speeds. Then, from late 2012 into 2013, the company put the program on what Saia described as a sabbatical, slowing it up to align it with the airframe’s progress.
In the meantime, the A320neo program progressed on schedule, leaving little time for Pratt to dwell on any disappointment about the MRJ delay.