Honeywell Develops Cooling System Upgrade for F-35 Engine

Honeywell has a fix for the F-35's engine cooling needs. (Image: Honeywell Aerospace)

Honeywell has demonstrated the ability to upgrade the current cooling capacity of the F-35’s Power and Thermal Management System (PTMS) to 80kW. With this significantly enhanced cooling capability, Honeywell now far exceeds the current 32kW cooling needs of the U.S. military and its allied partners.

In a 15-page Government Accountability Office (GAO) report published in December 2023, data provided by the Department of Defense (DoD) showed that the cooling systems featured on current in-service F-35 jets are overtasked, requiring the engine to operate beyond its design parameters. The extra heat is increasing the wear on the engine, reducing the engine’s life, and adding a projected $38 billion in maintenance costs over the life of the aircraft, according to the report.

The program has assessed some engine and cooling improvement options, but the military services have not fully defined future aircraft cooling requirements. DoD is now in the sixth year of a $16.5 billion modernization effort — known as Block 4 — to upgrade the F-35’s hardware and software systems. The agency intends for Block 4 to help the aircraft address new threats that have emerged since aircraft’s original requirements were first established in 2000.

"The PTMS, a system designed by a Lockheed Martin subcontractor, uses air pressure from the engine to provide cooling to aircraft subsystems that generate heat, such as the radar, to ensure they do not overheat and fail. It is a complex subsystem that includes the equipment necessary to provide aircraft main engine start, emergency power, cockpit conditioning, equipment cooling, and some electrical power," GAO notes in the December 2023 report. "Because the original estimates of the need for cooling proved to be incorrect, the PTMS uses more air pressure from the engine to cool subsystems than originally specified in the requirements, which is reducing the life of the engine and increasing costs."

Honeywell has now proven that it can offer a low-risk and affordable solution that meets the fighter jet program's future needs all while utilizing the existing supply base and sustainment network.

To demonstrate the 80kW cooling capability, Honeywell used a Digital Twin of the PTMS, which utilized data from over 2,500 hours of performance testing in Honeywell’s test facility, and more than 750,000 hours of in-flight experience. The Digital Twin incorporated low-risk advancements to heat exchangers and controls changes that further optimize system performance. These modest changes significantly increased cooling potential, while simultaneously maintaining all existing critical interfaces with airplane thermal systems without invasive redesigns or concurrency.

“Today, we have successfully demonstrated that we not only meet the F-35’s current operational needs, but we are ready to service future F-35 modernization upgrades without the need for expensive changes to the aircraft for either forward-fit or retrofit scenarios,” said Matt Milas, President, Defense and Space, Honeywell Aerospace Technologies. “By enabling F-35s to update cooling capacity within our existing PTMS architecture, we can now eliminate the risks that would otherwise come from qualifying and fielding a new system that would cost taxpayers billions of dollars without any additional benefit.”