MIDDLETOWN, CT -- The F-35 program is approaching its first wave of scheduled engine maintenance in 2023, and in preparation, engine-maker Pratt & Whitney is readying its architecture and processes for what the company views as a test of whether the engine sustainment enterprise is positioned to maintain readiness as it takes on additional workload.
The forthcoming scheduled depot work -- which is slated to begin at least two years later than previous projections due to lower aircraft utilization rates -- comes as the broader program chases a cost-per-flying-hour target of $25,000 by 2025. According to Pratt officials, that means the engine portion of that metric is set to rise just as the rest of the program’s costs are trending lower.
Speaking with reporters during a visit this week to the company’s Middletown, CT, production facility, F-135 Vice President Jennifer Latka said Pratt has “identified opportunities” to cut about 36% of the cost of the first scheduled maintenance visit.
F135 Sustainment Director Amanda Glode said the company anticipates the cost will be on par with that of legacy programs. However, because of where the engine sustainment effort is in its lifecycle, the cost trajectory doesn’t necessarily align with the JPO’s flying-hour cost targets.
“There is improvement coming,” Glode said. “It’s just not necessarily dialed in to all of the models that the JPO is using right now for planning purposes.”
Examples of measures Pratt has taken to lower costs include reducing the number of days an engine module is in depot or developing repairs before an engine arrives at the depot. The company is also learning from the unscheduled repairs and limit-expansion work it has performed to date, which Glode said will also help.
But perhaps the best way to reduce engine sustainment costs, Glode said, is to keep them on wing longer and lower demand for both scheduled and unscheduled maintenance.
“If we can use parts for longer or combine events into one so the engine only comes off wing once, those are some of the focus areas,” she said.
The program’s current strategy calls for scheduled maintenance approximately every 2,000 flight hours, Glode said, and as the company seeks to keep the engines flying longer, it may see that interval stretch longer or it may be able to extend the life of the engine hardware.
Those results will likely materialize in the first scheduled maintenance wave in the mid-2020s. Costs will still go up during that phase, she said, but the intent is to contain them where possible.
“We’re trying to bend the curve and make it slope less,” Glode said. “It’s never going to go away. You’re never going to be flat. It’s just the nature of propulsion. It comes in sine waves as scheduled maintenance comes and goes.”
Meanwhile, as the first scheduled maintenance cycle approaches, the program has struggled over the last year to meet unscheduled maintenance demands while maintaining engine availability.
The Pentagon revealed early this year the program was facing an engine backlog at its Heavy Maintenance Center at Tinker Air Force Base, OK, due to a power module shortage. The backlog left as many as 41 F-35As without engines in July.
Glode told reporters this week approximately 9% of the fleet is currently non-mission capable due to engine issues -- below the program’s 10% NMCR threshold requirement, but higher than its 6% objective.
“It’s been a tough 2021 because of power modules,” she said, noting that prior to this year, the NMCR for the F135 typically hovered around 4%.
While the F135’s mission capable rate does fall within the customer’s requirement, Glode said the company understands the frustration, especially because legacy Air Force programs have typically required a 0% NMCR and have had the spares and the depot capacity to support that performance.
The F-35 program, however, is spared at lower levels -- around 11% for engines compared to about 25-30% for legacy programs -- and early funding issues delayed depot capacity standup.
“We’re very comfortable working in any construct that the customer requires and certainly we’ve been encouraging the JPO to work with the partners and the services to try and understand what ‘good’ looks like and how they want to change the program,” Glode said. “Because we hear and we understand the feedback that what is executed today is not satisfying. But we can’t go and change the program ourselves.”
Pratt has discussed with the JPO the prospect of increasing the program’s engine spares ratio, Glode said, with a particular focus on the power modules. She said the JPO and the services are entertaining the idea.
“They see and they appreciate the fact that they have chosen over the years to make different outcomes because of what they’ve spared to,” she said. “It implicates some readiness challenges.”
But beyond spares, Glode said depot capacity presents a bigger challenge.
“The depot network is about five years behind in terms of where it should have been based on the program design and architecture, in large part because funds were diverted earlier in the program because there were other needs,” she said. “Sustainment just didn’t get the budget that was required in a timely manner to set up that architecture.”
The program expects to make strides over the next few years to increase its depot footprint. Beyond the depot at Tinker AFB -- which can perform a wide range of engine maintenance -- Australia, Norway, Japan and the Netherlands are upping their production capacity and will each come online between now and 2024. And the Navy’s depot in Jacksonville, FL, is expected to be fully activated for the F-35 in 2023.
Glode said there has also been a focus over the last 18 months on making sure the depots are appropriately staffed, mechanics are sufficiently trained and technical data and support equipment is in place.
“So, capacity is expanding,” she said. “Lots of lessons learned, lots of hard work, lots of corrective actions in place, and we feel like we’re on the right glide slope to continue that growth over time. And certainly that will be helped by the additional capacity coming online from those other sites.”
Latka said the program has seen a particular improvement at Tinker AFB, where maintainers are on track to “significantly exceed” their power module production target of 40 modules. Last year, the Heavy Maintenance Center produced just 14 modules.
The Tinker depot has also reduced its turnaround time from about 200 days in 2020 to an average of 120 days.
“They’ve just had a tremendous amount of progress this year, and that’s really a testament to the joint Tinker and Pratt & Whitney team that’s in Oklahoma and the JPO,” she said.