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Pratt & Whitney anticipates F135 ECU critical design review in mid-2025

Pratt & Whitney F135 engine on a test stand. (P&W)

Pratt & Whitney anticipates completing its critical design review (CDR) of the F135 engine core upgrade (ECU) in mid-2025, company F135 programme manager Jenn Latka told reporters on 6 February.

“Our design phase is supposed to end in roughly the middle of 2025 [with] the critical design review, and our first engine [goes] to test in 2026,” Latka said. The first ECU-equipped engine is scheduled to enter service in 2029.

“We are on track to hit all of those milestones, design is going very well on ECU,” Latka continued.

The ECU is intended to provide more power for electronics aboard the F-35's upcoming Block 4 version. The Block 4 requires about 25% more electricity to power its larger computer processor and more complex weapons systems.

The company has roughly 500 people working on a digital design of the ECU, Latka said.

“We are working in a model-based systems engineering environment with ECU, so if we make one little design tweak to a part, it is running through an integrated model – all the structures analysis, all the thermals analysis, etc,” she added.

The US Department of Defense (DoD) selected the ECU in March 2023 over a new General Electric engine called the Adaptive Engine Transition Program (AETP). Both the ECU and AETP would generate more thrust and electrical power than the current F135 engine, but the equipment AETP required proved unable to fit inside the F-35B variant.

AETP relied on ‘third-stream' technology by which the engine could switch between high thrust and high efficiency, and both Pratt & Whitney and General Electric continue to work on completing third-stream engines.

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