Pratt & Whitney will lean on its growing but saturated engine overhaul network to mitigate the ramifications from years’ worth of production-quality mistakes requiring hundreds of PW1100G engines to be pulled from service, and could see 650 Airbus A320neos grounded early next year.

A “fleet management plan” unveiled by Pratt parent RTX, formerly Raytheon Technologies, on Sept. 11 laid out the painful reality for affected A320neo operators. Pratt, with the backing of regulatory mandates, will pull 600-700 engines in the next two years for accelerated shop visits in addition to 500 or so already scheduled for overhauls. Most of the unplanned removals will come by “early 2024,” said RTX President and Chief Operating Officer Chris Calio. This includes 137 that must be pulled by the end of September.

The engines will be torn down and high-pressure turbine (HPT) stage 1 and stage 2 disks, or hubs, will be inspected for possible cracks. Pratt is projecting an eye-watering 250-300 days to turn each engine around—a function of an overhaul network already overbooked with PW1000G-series engines that need restorative shop visits to offset long-running durability issues.

Add it up and A320neo operators could see a peak of 650 aircraft on the ground awaiting at least one airworthy engine at the peak of the shop visits, projected to be sometime in the first half of 2024. Pratt is expecting the grounded aircraft count to average 350 aircraft through 2026.

“The impacts to our customers vary,” Calio said. “Certain operators are impacted more than others. We’re working operator by operator on mitigation and support plans.”

The flagged engines are part of a subset of 3,000 made from mid-2015 to mid-2021 that may contain high-pressure turbine (HPT) or high-pressure compressor (HPC) disks containing contaminated powder metal (PM), a common ingredient in engine parts.

Microscopic bits in PM—if they are not detected and wind up incorporated into parts—can lead to cracks. In the case of these parts, Pratt’s traditional inspection methods used during production did not detect the contaminants.

“We somehow or other introduced a contaminant into the powder,” RTX CEO Gregory Hayes says. “But it wasn’t a contaminant that we’d ever seen before.”

The problem was discovered during the investigation of a March 2020 engine failure on a Vietnam Airlines Airbus A320ceo. In that case, a contaminated IAE V2500 HPT stage 1 disk failed.

“We made improvements to the powder metal production process, and a new angle ultrasonic inspection was deployed,” Calio said. This replaced a long-used linear inspection.

Pratt’s analysis flagged a small batch of V2500 parts with contaminated PM. It later broadened its root-cause analysis to look at parts on other engines made during the same time period, which Pratt narrowed down to late 2015 through mid-2021.

That turned up more affected parts, including some on current-generation PW1000G-family engines.

Pratt developed fleet plans, and regulators mandated them. A 2022 FAA airworthiness directive flagged 189 engines on U.S.-registered aircraft and mandated disk inspections during routine, service life-driven shop visits that happen every 7-10 years. It was based on a Pratt service bulletin that lists nearly 2,100 affected PW1100G-series disk serial numbers, which appear to be the entire population of A320neo engines that have contaminated PM.

But Pratt’s probe of a December 2022 engine shutdown on a PW1100G-powered A320neo prompted a broader reexamination of the PM problem.

“Investigation of that event caused us to increase our assumptions on the likelihood of a GTF powder metal part having a crack at the time of manufacturing,” Calio said.

A closer look at inspection results coming in led to more changes.

“We found cracks that were larger than we had anticipated, which required us to increase our assumption on the rate at which a crack would grow,” Calio said.

On an earnings call in July, RTX revealed the anticipated ramifications of Pratt’s findings. About 200 engines need accelerated inspections by the end of September 2023, and perhaps 1,000 more will need checks by September 2024, the company said.

The updated fleet management plan cuts the overall number of early removals but also compresses the window in which they will take place.

“Since our call in July, we’ve now developed a holistic fleet management plan that ensures the continued safe operation of the fleet while balancing the impact to our customers,” Calio said.

Pratt’s current assumptions call for inspections every 2,800-3,800 cycles, depending on engine thrust ratings. The parts under scrutiny have a new, reduced life limit of 5,000-7,000 cycles.

Aviation Week Tracked Aircraft Utilization data shows the busiest  A320neos fly 200-250 cycles per month. At that rate, the highest-thrust engines would need inspections roughly every year. With turnaround times approaching 10 months, affected operators will be clamoring for permanent fixes.

An Aviation Week analysis shows more than 900 Pratt-powered A320neo-family aircraft were rolled out in the time frame that matches when the suspect engines were made and delivered to Airbus. India’s IndiGo operates the most by far, with 135. Five other carriers—Air China, Go First, Volaris, Spirit Airlines and Lufthansa—each have at least 40.

Pratt’s goal is to replace as many turbine and compressor disks as possible during the overhauls with parts made since the third quarter of 2021, when the PM issue was resolved in production. But it will not be able to make enough disks to send each engine home with new, problem-free parts, leaving some operators exposed to periodic inspections.

The OEM has no plans to divert spare engines from its pool of planned deliveries to Airbus, which is ramping up A320neo production, Calio said. If more spare engines become available, it will be from an overall boost in PW1100G output, he suggested.

Instead, the MRO network’s expansion will become a central focus.

“The best thing that we can do to help operators is, yes, continue to produce the spare engines that are in the plan and try to ramp that to the extent that we can, but [also] driving the industrial ramp needed for MRO output,” Calio said.

Pratt was adding PW1000 overhaul capacity to help address the engine family’s durability issues before the severity of the HPT disk problem became clear. It said in April that it had 12 shops globally that could handle PW1000 work and planned to add seven more by 2025.

“We’ve had some part constraints and shortages and labor in our MRO network, which has impacted our ability to output MRO to the levels that we and our customers want, which is why we’re adding more capacity to that MRO network,” Calio said on an April earnings call.

Timelines for opening these new shops are being accelerated where possible to help offset the PM issue’s ramifications.

“We are completely focused on ramping up production on HPT and compressor disks driving capacity throughout our MRO network, and reducing the turnaround time in our shops so we can get these assets back to our customers as quickly as possible,” Calio said.

The fleet management program will cost Pratt and its PW1000G program’s partners $6 billion-$7 billion, RTX estimates. The charges, which will cover labor for inspection and customer compensation, include $3 billion-$3.5 billion for RTX, which plans to take a $3 billion charge this quarter to help reflect the costs. The rest will be shared by the PW1000G’s risk-sharing partners.

Customer compensation will account for 80% of the costs, with the rest covering shop-visit labor and materials.

Still to be determined is how the PW1500G-powered Airbus A220 and PW1900G-powered Embraer E-Jet E2 fleets will be affected. Pratt is still analyzing the PM risk and determining potential risk-mitigation strategies. Executives are confident that any disruption to the affected A220 and E2 fleets will be minimal compared to what A320neo operators will face, however.

“We’ll have [a plan] in place for the PW1500 and PW1900 soon,” Hayes said.

The Aviation Week Network Fleet Discovery database shows about 260 PW1500G-powered A220s and PW1900-powered E2s were built when PM-contaminated disks were produced, along with 450 V2500-powered A320ceo-family aircraft. Executives are confident that after multiple revisions, they now have an effective plan for fixing the PW1100G fleet, and are confident the V2500 inspection regimen is good enough to detect any issues.

Pratt and RTX declined to answer multiple Aviation Week queries.