Aviation systems manufacturer Honeywell aims to have its power-and-cooling upgrade for Lockheed Martin’s F-35 fighter ready as soon as 2027.
That is according to Honeywell president of defence and space technologies Matt Milas, who says Honeywell intends to have the system ready within a few years – at about the same time Pratt & Whitney (P&W) starts rolling out a separate F-35 engine upgrade.
The Pentagon has not yet decided how it will address the long-term need for more power generation and thermal management capacity aboard the advanced combat aircraft, saying the decision will be left up to prime contractor Lockheed.
But Honeywell is positioning itself to provide the solution with an upgrade to the F-35’s existing Power and Thermal Management System (PTMS), which it produces. A competing proposal has also been announced by Collins Aerospace.
“We’re looking at how we can meet the needs of the [US] air force and other partners, [with] up to 80kW of cooling,” Milas told FlightGlobal during the recent Air & Space Forces Association (AFA) conference near Washington, DC. “We have solutions that are already designed and progressing through that evaluation.”
Honeywell’s current PTMS works in conjunction with the F-35’s P&W F135 turbofan to provide electrical power for onboard systems and to manage heat generated by the aircraft’s powerful sensors.
However, as capability improvements have been made to those systems since the F-35’s debut, onboard power and cooling requirements have increased. That requires diverting additional “bleed air” from the powerplant to the PTMS, reducing engine performance and increasing degradation.
While P&W maintains the F135 can operate under such conditions, it comes at the cost of longevity. A report from the US Government Accountability Office (GAO) found that overtaxing the F-35’s engine could add $38 billion in extra maintenance costs to the F-35 programme.
The Pentagon responded in late 2023 by awarding P&W a lucrative contract to develop an engine core upgrade (ECU) for the USA’s three F-35 variants. The programme is expected to generate billions of dollars in revenue for the engine maker over several years. Rival GE Aerospace had unsuccessfully pushed for Washington to nix the F135 powerplant entirely and replace it with a next-generation “adaptive” engine based on GE’s experimental XA100.
P&W aims to have its upgraded F135 engines flying on operational fighters as early as 2029.
With that target in mind, Honeywell wants its PTMS upgrade ready by 2027 or 2028, potentially allowing jets to undergo both upgrades simultaneously. “I think it would be really beneficial if we could get it into that same timeframe,” Milas says.
Hitting that target depends on if and when Lockheed hires Honeywell to supply the PTMS upgrade. Milas says the upgrade will be a “drop-in” design, making it relatively quick and easy to install even if the timeline slips beyond P&W’s ECU plan.
“A new PTMS that is the same envelope, same interfaces, same everything, probably will not be very disruptive,” he says.
However, decisions made by the Pentagon and Lockheed could necessitate more work. If Pentagon brass desire more cooling capacity than Honeywell’s PTMS upgrade can provide, changes to the F-35 airframe could be required.
Although reaching the 80kW output target will require additional cooling capability, Milas says Honeywell’s PTMS upgrade would not require changing the F-35’s structure. The company is also studying tweaks to the existing PTMS that could generate additional cooling, potentially reaching 40kW output.
This would reduce demand for engine bleed air, which is a primary culprit behind maintenance issues generated by overtaxing the F-35’s power supply.
While the Pentagon showed preference for upgrading the jet’s existing engine rather than developing a new powerplant, it remains unclear if the government will follow a similar strategy when addressing power and cooling requirements.
Honeywell rival Collins – a sister company to F-35 propulsion supplier and fellow RTX subsidiary P&W – has entered the fray with a competing solution. Collins announced its proposed Enhanced Power and Cooling System (EPACS) at the Paris air show in 2023.
Honeywell immediately fired back. It says replacing the PTMS with a new design would cost US taxpayers at least $3 billion – far more than a PTMS upgrade.
US Air Force (USAF) funding requests offer some insight into the service’s intentions.
In fiscal year 2025 budget documents, submitted this year, the USAF says it began funding a PTMS upgrade in 2024. The service received $266 million in the FY2024 budget to fund programmes related to modernising the F-35’s engine, power and thermal management systems.
The FY2025 budget request includes just under $268 million for the same purpose, with $27 million in dedicated funding for engineering and development work to mature a PTMS upgrade design.
USAF spending plans indicate the F-35 family of jets will require additional cooling capacity starting in production Lot 22, scheduled to begin in 2028.
“Due to the massive leap in cooling and power needed to support post-2029 mission system upgrades on the F-35, the existing PTMS will need to either be massively upgraded or replaced,” the USAF says.
While the service has concluded that capable solutions exist, “it is unclear which system will be best”, air force officials say.
The service plans to mature multiple potential solutions and leave prime integrator Lockheed to select the power and cooling system that “best meets the government’s cost, schedule and performance needs”.
The service apparently concurs with Honeywell that the existing PTMS can be upgraded within the existing housing bay and using available components that are “relatively low-cost and already at a high technical readiness level”.
Developing, certifying and building out production capacity for such a programme would take five to six years, according to USAF estimates.
