Farnborough Air Show

Pratt & Whitney Heeds Hard Lessons Learned on GTF

 - July 11, 2018, 10:00 AM
Pratt & Whitney PW1100Gs powering Airbus A320neos in India, such as those at IndiGo, have faced a disproportionate level of scrutiny due to such problems as a design flaw in the knife edge seals in the engines' HPC aft hub. (Photo: Airbus)

Pratt & Whitney appears to have reached a point at which it can turn more of its attention toward proactive improvements to its geared turbofans after it reverted to a previous knife-edge seal configuration in the PW1100G’s high-pressure compressor aft hub in reaction to a series of rejected takeoffs and in-flight shutdowns in Airbus A320neos. Speaking last month at the company’s Digital Accelerator facility in Brooklyn, New York, Pratt & Whitney Commercial Engines president Chris Calio told reporters that engineers continue to explore new designs for the seal, as part of standard practice to pursue continuous improvement in the overall engine design.

“We’re still looking at what we may want to do to that seal long-term,” said Calio. “There may be an upgrade that we want to put in place from the current configuration in the future.”

Calio acknowledged that the problem taught Pratt “kind of a hard lesson” in terms of the testing rigor it needs to employ before inserting upgrades. “What we’re ultimately going to do to this knife-edge seal to the extent that the engineers come back and they want to make a more robust design, it will be through an increased set of testing,” he explained. “There will be some durability and other upgrades to the engine, some of which we talked about, which will go through more intensive testing. In some cases, we will have taken the original timeline and pushed it out to the right in order to allow for more of what I would call less success-based testing.”  

Calio, meanwhile, noted that Pratt had a few weeks earlier met its first commitment milestone for deliveries to Airbus and expressed confidence that the engine company would deliver the number it has promised for the year, although it declines to specify the exact figure due to competitive considerations. “[Parent company] UTC has been very public about what our negative margin engine losses are per year, so because of that, if we put out an exact production number, my competitor can pretty much calculate what my loss per engine is and calculate what my price is,” explained Pratt & Whitney president Bob Leduc.

Having delivered 374 GTFs last year, Pratt & Whitney has set a target of 2,500 over the next three years, requiring a considerable ramp up next year and in 2019. Although it doesn’t give exact figures for 2018, it has said it plans to roughly double its output from 2017. “Doubling can be interpreted in different ways by different people,” said Leduc, however.

Leduc also said the prospect of increasing production for Airbus to accommodate a rate of 70 A320neos per month would depend on Pratt’s own supply chain, and that he has not even talked with the relevant suppliers about it.

“Nobody’s committed to rate seventy,” said Leduc. “That’s certainly not what our commitment to Airbus is and I don’t think it’s our competitor’s either. We have a commitment that’s in the sixties; we are on track to meet that commitment in the time frame we said we would. Anything beyond that requires a fair amount of study with the supply chain. As [vice president of operations] Shane [Eddy] said, castings and forgings are sort of the long pole in the tent, and there would have to be a discussion with all of those suppliers as it relates to that. We have not engaged the suppliers in that conversation because we’re not obligated to go above the rate we’re committed to.”  

Addressing Airbus’s A320neo delivery delays, the cause of which stemmed from technical problems with both the PW1100G and the other engine choice, the CFM Leap-1A, Calio explained that the knife-edge seal configuration change in the Pratt engine caused a pause in production early this year, thereby interrupting the flow of deliveries to Airbus. “[The delivery flow] was not in the linear fashion that I think Airbus would have wanted,” he acknowledged. “From an engine delivery perspective, we believe we are caught up and on track to meet the commitments Airbus laid out for the year...Again, I’m not absolving us from putting some strain on Airbus, because we did do that. We didn’t deliver to them in a linear fashion; it was more back-end loaded.”

Calio noted that the new liftoff seal and combustor improvements to the PW1100G will also apply to the PW1500G and that Pratt would finish installing them on the C Series this year. “Everything we’re learning on the neo early on in the last two years we’re putting onto the C Series,” he said. “So that’s about a six-month lag between the improvements on the neo into the C Series. But we expect all those benefits to flow through.” 

Although all engines delivered today contain the new knife-edge seal configuration, combustor fixes, and new liftoff seals needed in both GTFs in service, A320neo operators, most notably in India, still fly several engines in their original configuration, requiring eventual removals. “So we’re still going to be challenged with making sure we have enough spare assets, when we need them, where we need them, to keep the India fleet off the ground,” said Calio. He projected that all engine removals involving IndiGo and Go Air neos will occur “at some point in early to mid-2019.”