The ‘P40’ upgrade to the F-35’s existing systems would offer a 25% increase to onboard cooling capacity.
Honeywell Aerospace has unveiled its proposal to upgrade the power and cooling system installed on the Lockheed Martin F-35 stealth fighter.
The aerospace manufacturer says its “P40” solution will offer a 25% increase to the F-35’s onboard cooling capacity, increasing to 40kW from the current 32kW level.
Importantly, the P40 upgrade would be a modification to the Lockheed fighter’s current Honeywell-made Power and Thermal Management System (PTMS), using software updates and “targeted liquid-cooling enhancements”. Honeywell has hinted for over a year that it was developing such an upgrade.
The company says the package will not require any airframe modifications and can be rolled out in tandem with the ongoing Engine Core Upgrade programme to overhaul the F-35’s single Pratt & Whitney (P&W) F135 engine.
“Operators need additional cooling capacity and improved readiness on a timeline that matters,” says Matt Milas, president of Honeywell’s defence and space unit. “P40 delivers both by building on the proven PTMS architecture already operating across the global F-35 fleet. It provides meaningful near-term cooling growth while preserving a scalable path to support future modernisation requirements.”
The PTMS is a key component on all three F-35 variants, cooling each jet’s powerful sensors and electronic systems.
However, improvements to the multinational fighter’s onboard systems since its original design have left the F-35 operating outside its original design tolerances for power and cooling, requiring more frequent maintenance on the F135 turbofan and increasing long-term sustainment costs.
That led the Pentagon to pursue a multibillion dollar engine core upgrade for the F135, which P&W is designing.
Rival enginemaker GE Aerospace had pushed for a complete engine replacement, offering up its XA100 as an alternative to the F135, promising substantial improvements to aerodynamic performance and range. The Pentagon ultimately opted to upgrade the existing powerplant after a multi-year industrial battle.
A similar situation is now unfolding around the PTMS, which government auditors say will also need to be upgraded to allow for new weapons, sensors and communications to be incorporated into the F-35 over the long term.
RTX subsidiary Collins Aerospace has proposed an entirely new mechanism it calls the Enhanced Power and Cooling System (EPACS), while Honeywell is suggesting a more modest upgrade to the existing PTMS.
As with the engine debate, the incumbent Honeywell argues that an upgrade will be cheaper and faster with less engineering risk, while the competitor Collins is pushing for a wholesale replacement on the promise of substantial performance increases.
Collins has long said the EPACS will be able to more than double the F-35’s current cooling capacity with a potential output of 80kW. The company completed simulated high-altitude testing on the EPACS prototype in August.
Honeywell says its P40 package will be ready to field between 2029 and 2030 – a roughly similar timeline to the F135 engine upgrade programme.
The Pentagon and F-35 prime contractor Lockheed Martin have not yet made a formal decision on how they will handle the PTMS upgrade.
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