Pratt & Whitney says more frequent geared turbofan disk inspections needed
By Sean Broderick July 25 2023
A fresh look at data gleaned from shop visits has led Pratt & Whitney to consider shortening inspection intervals on more than 1,000 PW1100G-JM engines with a suspected manufacturing problem, setting affected operators up for potentially significant fleet disruptions well into 2024.
Inspections of high-pressure turbine stage 1 and stage 2 disks made from late 2015 through early 2021 and flying on Pratt-powered Airbus A320neos have been mandated since late 2022. Pratt’s previous analysis concluded the checks—which require removal and disassembly of the engine—could wait until scheduled maintenance shop visits. But updated analysis from recent inspections led Pratt to conclude more frequent checks are needed, the company revealed July 25.
The process will start with a surge of checks in the next few months.
“Based on the current assessment, Pratt anticipates by mid-September that approximately 200 PW1100 engines will be removed for enhanced inspection,” Chris Calio, President and COO of Pratt parent RTX, formerly known as Raytheon Technologies, said on an earnings call.
Results from those checks will help determine the next steps, including any inspection interval revisions.
Pratt is anticipating that another 1,000 engines will require inspections by mid-2024, “but the exact number of engines and the timing of those removals is not yet finalized,” Calio added.
The affected engines have one of some 2,070 PW1000G-JM stage 1 and 2 disks flagged by Pratt as containing contaminated powder metal (PM) that can reduce a part’s service lift.
The problem was discovered during the probe of a March 2020 engine failure on a Vietnam Airlines A321ceo. In that case, a contaminated IAE V2500 HPT stage 1 disk failed.
Pratt’s initial analysis flagged a small subset of legacy engine parts with contaminated PM. It later broadened its root-cause analysis and found more affected parts, including some on current-generation PW1000G geared turbofan (GTF) family engines. The findings prompted regulatory mandates, but they affected only a handful of parts on V2500s and several PW1000G variants.
Further analysis flagged the 2,070 disk serial numbers listed in a July 2022 service bulletin that also spelled out Pratt’s recommended inspection protocol. The FAA and other regulators mandated the checks, setting the interval as the next scheduled shop visit.
Every inspection yields new data, which Pratt incorporates into its service-life model for the parts.
“Based upon everything that we knew until very recently, we believed that the life of the turbine disk was such that we would see these disks in the shop and be able to inspect them before we ever had an issue,” RTX Chairman and CEO Greg Hayes said. “As we looked at the data again over the last couple of months, our safety risk assessment [experts] went through their process of updating the data based on all the recent findings. And they said, ‘You know what, we’re not absolutely positive that the lifing model is accurate. We want to take a look at these disks at a much-accelerated basis.’”
Potential Disruptiveness
The near-term ramifications for affected operators is unclear. Some of the inspections can be done during already scheduled shop visits, while others may lead to slight changes in airline maintenance schedules.
But many are expected to take place well before airlines had planned them, which could lead to significant fleet disruptions.
“Right now, we’ve got to now work through how we define the work scope and the turnaround time that’s required,” Calio said. “GTF is going to have a lot of shop visits here in the back half of 2023 and into 2024. We need to figure out how many of those are incremental and what the true impact of the fleet is, but that’s ongoing.”
The Aviation Week Network Fleet Discovery database shows about 920 A320neos were delivered from late 2015 to early 2021, the time period when the suspect disks were made. Indian LCC IndiGo has the largest potentially affected fleet by far, at 135 aircraft. Others with sizable numbers include Air China (46), Go First (45), Volaris (44), and Spirit Airlines (43).
Volaris extended leases on six aircraft that were supposed to exit the fleet in 2023, in part to help offset both new aircraft delivery delays and engine availability issues. Volaris CEO Enrique Beltranena said it was too early to calculate the real impact of the latest issue with the PW1000G engines, “but I think [Pratt] has the provisions and has been working on an accelerated way to try to control the impact.”
The new wave of inspections will add complexity for some airlines that have seen their GTF fleets plagued with durability issues and premature engine removals for years. An Aviation Week analysis of Tracked Aircraft Utilization data in April found 11% of all PW1000G-powered aircraft, mostly A320neos and A220s, were either grounded or flying less than once per week. In many cases, airlines were waiting for Pratt to provide needed spares or free up slots in engine shops to make needed repairs.
Pratt has been adding GTF overhaul capacity to its network as part of a planned ramp-up to meet both scheduled overhauls and address the long-running durability issues. Pratt has 13 GTF overhaul shops and planned to add six more by 2025. That timeline and near-term support strategies are shifting, however.
“We’re going to have to accelerate some of the tooling,” Hayes said. “We’re going to have to dedicate some spares to a rotable pool of engines to support some customers.”
Pratt also is developing a “project” shop visit to handle the new checks that minimizes the required work and related engine downtime, Calio said.
“When you think about that 2024 shop visit population, we’re going to take a look at the utilization on those … and working with our customers making a decision, a mutual decision on ‘is this the right candidate for a project visit? Or should that work scope increase to take on additional work, which will benefit the time on wing and the interval of that engine moving forward several years?’” Calio said. “That is a conversation that we will have once we better understand again how many of these visits are truly incremental in 2024 and then [what are] the related fleet impacts.”
“We’ve got this,” Hayes added. “It’s going to be expensive. We’re going to make the airlines whole as a result of the disruption we’re going to cause them.”
The PM issue, linked to material supplied by a Raytheon-owned plant and processed at Pratt’s Columbus, Georgia, manufacturing facility, was corrected on the production line in 2021, so recently delivered engines are not affected.
“New engine families do have reliability issues, whilst the aero supply chain problems are well known—the fact that this latest issue is all internal arguably makes it worse,” wrote Vertical Research Partners analyst Robert Stallard. “But at least it has been spotted and should be addressed over the next year or so.”
Among the few slivers of positive news is that Pratt’s inspections have yielded few disks—less than 1% of the 3,000-plus examined from multiple Pratt and IAE engines—that needed immediate replacement.
“Of course, if we had to replace the turbines, then we’d factor that into the turnaround time,” Calio said. “But our assumption, based on everything that we’ve seen thus far, is that the fallout rate [on the new inspections] will be very low.”
