F-135 Block 4 Advances As RTX Pratt & Whitney Completes Engine Core Upgrade Preliminary Design Review

Engine manufacturer Pratt & Whitney (P&W) announced on Monday that it has completed the Preliminary Design Review (PDR) for the F-135’s Engine Core Upgrade (ECU). With this announcement, P&W confirms that the ECU design is “on schedule and exceeding expectations.”

The Preliminary Design Review

Throughout the PDR, the manufacturer looked at the proposed design changes as well as the technologies associated with the engine’s propulsion. In a statement, Chris Johnson, P&W’s vice president for the F135 program, said:

“Pratt & Whitney is upgrading the F135 engine with technology from multiple development programs to deliver increased capability and performance for the warfighter. Upgrading the F-35’s propulsion system to ECU is a critical step toward ensuring the F-35 remains the world’s premier air dominance fighter.”

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The ECU, as proposed by Pratt & Whitney, is the only modernization solution available for the F35’s propulsion system, which the US Department of Defense selected in 2023. In March this year, the ECU received full funding as per the fiscal year 2024 Defense Appropriations bill. F-35 Propulsion Program Manager, US Navy Captain Mitchell Grant said:

“The PDR was a successful first step toward the capability the ECU will provide in meeting the challenging performance and durability requirements of the F135. The ECU will ensure that the U.S. and our international partners remain well positioned to outpace adversary threats.”

What is the ECU?

The ECU program is a block upgrade for the F135 engine, providing cost savings and operational improvements. The manufacturer says the ECU provides “an affordable, low risk, and agile pathway to fielding meaningful propulsion capability for all F-35 customers.”

Photo: Richard Whitcombe | Shutterstock

The restoration of engine life is essential for this aircraft, given that, according to Lockheed Aeronautics’ executive vice president, Greg Ulmer, the F-35 is expected to fly until 2070.

In an interview with AFM, Pratt & Whitney noted the improvements that the ECU will provide:

The ECU is the current iteration of those upgrades [undertaken over the past years] which will restore the engine to full life while increasing the power and cooling capacity needed to fully enable Block 4 and beyond capabilities for the F-35. P&W was selected by the US Department of Defense (DOD) to modernise the F-35’s propulsion system in 2023.

The manufacturer is targeting 2029 for the first deliveries of the upgraded F-35 engine. The first tests are expected to be run by 2026, and a critical design review will follow the PDR, with completion by mid-2025.

Controversy: Lockheed Martin and the Adaptive Engine Transition Program

F-35 manufacturer Lockheed Martin has publicly shared concerns over the choice of the ECU program in the past. In fact, back in June last year at the Paris Air Show, Lockheed Martin’s Ulmer said in an interview with Breaking Defense that “some” of the current approaches to the modernization of the F-35 engine are “short-sighted.”

“I’m going to advocate, and I do advocate, for [the Adaptive Engine Transition Program], another engine. I think some of the approaches today are very short-sighted and not considering a longer-term view [for the F-35].”

He believes that, given that the F-35 will fly for decades to come, additional upgrades will be needed later.

“Let’s put as much margin in the airplane as we can today, such that in the future, I don’t have to put another motor in. I don’t have to bring new power and thermal management cooling into the airplane.”

GE Aerospace, in particular, has been advocating for prototypes through AETP. Ulmer’s comments came at the expense of P&W, despite them being the ones chosen by both the US government and endorsed through funding. Contacted by Defense News, P&W responded that Ulmer’s statement “undermines” official governmental support to the ECU. President of Military Engines, Jull Albertelli, said:

“Lockheed Martin wants to put an unproven adaptive engine on a single engine fighter jet, regardless of the hefty price tag and the significant delay in delivering critical capabilities to the warfighter at a time of urgent need.”

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