F135 Depot Extends Rebound From 2020 Nadir, Sets Record Pace

Pratt & Whitney F135 engine
Credit: U.S. Air Force

The only heavy maintenance center for the Lockheed Martin F-35 engine plans to deliver 60-72 repaired power modules this year and ramp-up to an annual output of 120 in 2026, US Air Force and industry officials say. 

The maintenance center for the Pratt & Whitney F135 is rebounding from a dismal performance in 2019 and 2020, which led to an engine shortage and the grounding of more than 50 F-35s in the U.S. fleet by last year. 

In less than two years, a joint effort by Air Force maintainers and Pratt & Whitney process managers have slashed the average length of a depot visit for the F135 turbofan engine by more than half, says Col. A.J. Griffin, commander of the 76th Propulsion Maintenance Group at the Oklahoma City Air Logistics Center. 

The engine shortage has declined to the point where there are now 30 grounded F-35s in the U.S. operational fleet, Griffin says.

The Air Force expects the center to deliver at least 60 F135 power modules in 2022, but Griffin has set a stretch goal to ship up to 72 out the door. 

A power module comprises the core of the engine, which includes the combustor and the low-pressure and high-pressure spools. 

If funding is approved in future budgets, the center plans to ramp up to deliver at least 90 power modules in 2024, 105 in 2025 and 120 in 2026. 

The ramp-up contrasts with a slow start by the heavy maintenance center in 2019. 

As an unexpected spurt of unscheduled engine removals flowed into the Oklahoma City depot, power module deliveries stalled. Only 14 power modules were delivered in 2020, with each taking more than 240 days to repair. 

A series of process improvements quickened the pace. By October 2021, the center had reduced the interval for each power module to 122 days, Griffin says. To achieve the stretch goal of 72 deliveries this year, the interval must shrink to 105 days. 

Steve Trimble

Steve covers military aviation, missiles and space for the Aviation Week Network, based in Washington DC.