Losing four geared turbofan engines to in-flight failures as a result of a botched durability upgrade was not how Pratt & Whitney wanted 2018 to begin – quite the opposite.
The two-year anniversary of the entry into service of the PW1100G on the Airbus A320neo on 20 January seemed, at the time, a critical turning point. The engine had delivered on its promised fuel-burn performance, and now it was time to move past the supply-chain breakdowns and design glitches that had plagued the pace of deliveries to Airbus and Bombardier CSeries customers.
But then the next major problem appeared. Production halted for a month as P&W replaced a defective knife-edge seal installed in the aft hub of the high pressure compressor with serial numbers P770450 through P770614. Instead of moving forward, it was replacing a part that had been installed as an upgrade.
It is a measure of the progress achieved to date that Chris Calio, president of P&W Commercial Engines, could smirk at the irony of the situation during an interview in June.
"We did [the knife-edge seal upgrade] for durability," Calio says, then briefly pauses to acknowledge the contradiction. "And, of course, it didn't have that effect. We're back to the prior configuration, and we're still looking at what we may want to do with that seal long-term. There may be an upgrade that we want to put in place from the current configuration."
P&W has spent more than $10 billion to bring the family of geared turbofan engines to market. It picked the perfect time to introduce a new centreline engine with a novel technology – the fan drive gear system. The single device translates 30,000hp (22,400kW) transmitted on a shaft from a low-pressure turbine, allowing the front fan to spin at one-third the rate of the source of its power. That slower speed means P&W can extend the length of the fan blades, increasing the fan diameter and, thus, the bypass ratio.
So far, the fan drive gear system has delivered as promised, reducing airline fuel bills by double digits. The problem for P&W has arisen in unexpected places using conventional, proven technology. It follows a familiar pattern across the engine industry. P&W's rival for A320neo orders, CFM International, is still months behind on planned deliveries of Leap engines because of a lack of forgings and castings. Rolls-Royce seems in even worse shape, with approaching 50 Boeing 787s parked awaiting a promised fix for a growing pool of defective compressors in Trent 1000 engines.
The overlapping troubles have turned 2018 into something of a recovery year for the turbofan engine, a 50-year-old technology being pushed to new limits of performance amid an unrelenting super-cycle of record production. At the same time, the same manufacturers are facing new pressure from Boeing on pricing and aftermarket sales, while GE Aviation and R-R in particular are dealing with corporate-level financial difficulties.
For P&W, the outlook overall looks relatively bright. Lockheed Martin is ramping up production of the F-35 stealth fighter, which is powered by the P&W F135. Although the rate of PW1100G deliveries is behind schedule, the ramp-up is still faster than anything P&W has seen in high-bypass turbofan engine era. Once the design problems are behind it, the company's only challenge will be to catch up with CFM's orders lead on the A320neo-family backlog.
The company appears almost ready to move on. A raft of new performance and durability ugprades is being prepared. Opportunities for new applications of the geared turbofan architecture are being submitted. But the focus now remains on addressing the stockpile of durability problems that have accumulated over the last three years, and the company has taken stock of its situation.
"I think we all learned a hard lesson [on the knife-edge seal issue]," Calio says. "We were moving quickly to support the fleet and put upgrades in to help our customers."
P&W plans to take an intentionally slower approach to rolling out future durability and performance upgrades.
"In some cases, we've pushed [upgrades] out to the right to allow for less success-based testing. We will allow for learnings. We definitely learned our lesson from the knife-edge incident."
The production freeze in March did not help the recovery plan, but its impact is soon to be overcome. By early June, a backlog of about 100 assembled A320neos were waiting for PW1100G engines. Although A320neo engine rival CFM also is running behind on engine deliveries, Calio acknowledges the PW1100G's share of the problem.
"I'm not absolving us from putting some strain on Airbus, because we did do that," he says.
Echoing the company's message before the knife-edge seal problem appeared in January, Calio says P&W is now ready to move forward on the geared turbofan programme.
There is a lot to be done. CFM's Leap-1A has a growing lead over the PW1100G, but about one-third of Airbus's customers in the backlog have yet to decide between the two propulsion options. Meanwhile, P&W's supply chain is committed to delivering more than 2,500 engines over the next three years. The company delivered a total of 512 PW1000G-series geared turbofan engines in 2016 and 2017 combined. Beyond the family's five existing customers, P&W is also hoping to attract new applications, but has dropped consideration of switching to a different reduction-gear configuration for larger engines.
Although the company is ready to move forward, the immediate focus is still on completing the recovery from its original design mistakes.
"Some of these [removal issues] will continue to fly for a while," Calio says. "They will probably all get removed at some point – I want to say, early to mid-2019."
As each engine is removed, the pressure is on P&W to have enough spare engines on hand to keep all of the aircraft flying. The need for a larger pool of spare PW1100Gs will continue for months after the last engine is removed from an aircraft. The timeline for returning all removed engines from the shop could still "leak into 2020", Calio says. The pace will be driven by the "turnaround time at our MRO shops", he adds. "Many should get back out in 2019."
A special focus will be on the return-to-flight of several PW1100G-powered A320neos in India. Two of the initial A320neo operators, Go Air and IndiGo, have been hit especially hard by the PW1100G problems, with Indian regulators taking a hard stance on precautionary groundings.
"The highest proportion of our fleet is today between IndiGo and GoAir. So we've had to stay very close to the customer and the regulatory authorities there because, I think, there has been a higher sense of scrutiny," Calio says.
"In India you still have a fair amount of engines with the prior configuration," Calio says. "We're still going to see those removal events. We're still going to be challenged making sure we have enough spare assets."
Source: Cirium Dashboard