The following is the Dec. 2, 2022, Congressional Research Service In Focus report, F-35 Joint Strike Fighter (JSF) Engine Options.
From the report
The Department of Defense (DOD) is considering whether to upgrade the F-35 Joint Strike Fighter’s (JSF’s) existing F135 engine—the Engine Enhancement Package (EEP)—or to develop and procure a new engine for the aircraft—the Adaptive Engine Technology Program (AETP). Congress has long expressed interest in issues relating to the F-35’s engine. Section 242 of the FY2022 National Defense Authorization Act (P.L. 117-81) required DOD to develop an acquisition strategy for transitioning the engine of the Air Force version of the JSF (the F-35A) to the AETP. Section 243 required DOD to develop a separate acquisition strategy for transitioning the Marine Corps and Navy versions (the F-35B and F-35C, respectively) to some form of advanced propulsion.
History of F135 Engine
The F135 —designed and built by Pratt & Whitney (P&W) of Middletown, CT—is the only engine that currently powers the F-35. (For more on the F-35 program, see CRS Report RL30563, F-35 Joint Strike Fighter (JSF) Program, by John R. Hoehn.) DOD awarded P&W the F135 contract in 2001. P&W decided to derive the F135 from the F119 engine, which powers the Air Force’s F-22 fighter, to speed up the F135’s development.
General Electric (GE) and Rolls Royce (RR), alternatively, collaborated to develop an engine for the JSF called the F136, and the F-35 program initially planned to use both engines. The Navy ended its participation in the F136 program. Following DOD’s F135 contract award in 2001, GE and RR continued to develop the F136. In FY2011, Congress ended development funding for the F136, and GE and RR announced in December 2011 that they would no longer continue developing the F136.
P&W has experienced design challenges with the F135 engine, such as bleed air requirements and sustainability issues. Air Force Lieutenant General Eric Fick, the Program Executive Officer for the JSF program, testified in April 2022 that DOD originally defined the F135’s requirements for bleed air (compressed air taken from within the engine) during early development. However, engine capability design modifications and new requirements emerged during the F-35 Continuous Capability Development Delivery (C2D2) program. The F-35 C2D2 program provides “incremental … improvements to maintain joint air dominance against evolving threats.” He stated that “[t]o provide the necessary bleed air, the engine was required to run hotter, and early engineering assessments suggest that this increase in operating temperature could decrease engine life, driving earlier depot inductions and an increase in life cycle cost.”
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