A squadron of F-35As flying over Hill Air Force Base in Utah. (Photo courtesy of U.S. Air Force)
The F-35 Joint Program Office (JPO) and Lockheed Martin are undertaking a Power and Thermal Management System (PTMS) analysis to specify what systems the fighter will need to have between 62 kilowatts and 80 kilowatts of power to accommodate dozens of new weapons and sensors in Block 4 and the future “Block X.”
The House Armed Services Committee’s (HASC) Tactical Air and Land Forces (TAL) panel said that the JPO and Lockheed Martin are to finish the analysis by the end of this year.
“To date, the Block 4 aircraft modernization program has been underfunded and has delayed timely completion of the aforementioned analysis and implementation of its recommendations,” according to the panel’s portion of the draft HASC fiscal 2027 defense authorization bill.
An “under-funding” of Block 4 is an open question, as cost estimates for Block 4 have swelled from an initial $10.6 billion to more than $16.5 billion.
“The committee is concerned that any further delays could interfere with modernizing the architecture of the aircraft to meet installation and usage of more advanced and effective combat mission systems,” the HASC TAL panel said. “The F-35 JPO must appropriately manage its responsibilities to develop and field Block 4 capabilities, inclusive of the critical supporting subsystems for which both Block 4, and future capabilities beyond Block 4, are dependent. The Department [of Defense] expects the F-35 to have a service-life into the 2070s. Therefore, maximizing capability growth margin for future cooling demands is critical.”
The HASC wants the Air Force and Navy to submit a report by December on PTMS modernization to avoid further delays. The F-35 program is not planning to start production of a Power Thermal Management Unit (PTMU) until 2033.
Honeywell builds the F-35’s current PTMS and is offering a version of that for PTMU, while RTX‘s Collins Aerospace is offering its Enhanced Power and Cooling System.
Multi-Year Procurement of F-35 and F-15EX
In addition to the language on Block 4 and PTMS for the F-35, the HASC TAL panel’s fiscal 2027 proposal also proposes multi-year procurement (MYP) of the fifth-generation multi-role fighter and the Air Force’s F-15EX fighter by Boeing.
The proposal would allow Defense Secretary Pete Hegseth to enter MYPs for procurement of both aircraft after providing a certification to Congress that the buys include “a full complement of initial spares and alternate mission equipment” and, for the F-15EXs, “conformal fuel tanks.” The latter are to give the F-15EX a ferry range of 2,100 nautical miles versus 687 nautical miles without the extra fuel.
A version of this story originally appeared in sister publication Defense Daily.
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