Pratt F-35 engine upgrade clears preliminary design review
The Engine Core Upgrade program is “on track” to field “as early as 2029,” according to Pratt & Whitney.

Breaking Defense

By: Michael Marrow

July 15, 2024


WASHINGTON — RTX subsidiary Pratt & Whitney has cleared an early design hurdle for a planned upgrade to the F-35’s engine, which the company maintains is “on track” to field by 2029.

“Pratt & Whitney is upgrading the F135 engine with technology from multiple development programs to deliver increased capability and performance for the warfighter,” Chris Johnson, Pratt’s vice president for the F135 program, said in a press release today. The F135 is the official designation for the F-35’s engine. “Upgrading the F-35’s propulsion system to ECU [Engine Core Upgrade] is a critical step toward ensuring the F-35 remains the world’s premier air dominance fighter.”

The design milestone, known as a preliminary design review (PDR), is a key step in the development process, which paves the way to more detailed work. A PDR, for example, typically must be in place before a major acquisition program can proceed with a Milestone B decision, which serves as the beginning of the engineering and manufacturing development phase.

The ECU enhancement effort is expected to offer improvements for features like thrust and fuel efficiency for the stealth fighter, and be compatible with all three F-35 variants. The Pentagon last year — not without controversy — opted against developing a brand new engine for the fighter, and formally sole-sourced the ECU work to Pratt, which manufactures the F135.

An upgrade to the current engine is needed, officials say, due to a cooling problem long known with the F-35. Essentially, the fighter’s engine is being overworked because its cooling system needs to draw more air pressure, known as “bleed air,” from its powerplant than designers originally expected, forcing the engine to run hotter and reducing its lifespan in turn. The upgrade is expected to restore engine life and offer better performance.

A suite of forthcoming upgrades to the plane itself known as Block 4 is expected to turn the F-35’s heat factor even higher and require more cooling as a result. Both Pratt and the F-35 Joint Program Office have said the ECU will not only address the bleed air issue but will fully enable Block 4 capabilities as well. The F-35 program is also planning a separate cooling system upgrade to address needs beyond Block 4.

A recent Government Accountability Office report raised questions about the timeline for the ECU’s fielding, with the watchdog stating that the F-35 program won’t deliver aircraft with updated engines until 2032. Still, in the time since and in responses to Breaking Defense today, Pratt maintained its goal of fielding the ECU by 2029.

“Completion of the PDR confirms F-35 propulsion modernization remains on track. Pratt & Whitney will continue ECU development and is positioned to support Initial Service Release as early as 2029,” Pratt said in a statement.

Pratt is separately competing against GE Aerospace to develop a new engine that will power a planned sixth-generation fighter for the Air Force. That engine effort is known as Next Generation Adaptive Propulsion, though service Secretary Frank Kendall recently raised the possibility that the program may need to explore redesigning the engine to bring costs down.

Click here to view this article as it originally appeared on the Breaking Defense website.