Collins Aerospace continues to press ahead with its bid to replace rival Honeywell Aerospace as the supplier of a critical onboard system for the Lockheed Martin F-35 stealth fighter.
The RTX subsidiary on 28 February said it successfully tested a demonstrator of the Enhanced Power and Cooling System (EPACS), which Collins hopes will eventually replace the F-35’s current power and thermal management system (PTMS) made by Honeywell.
Collins has long promised that the new system, unveiled in 2023, can deliver twice the cooling capacity of the current PTMS. The latest test of a fully-functional EPACS demonstrator indicate that goal is attainable, Collins now says.
“EPACS can deliver that cooling, and with our successful demonstrator test, we stand ready to begin the integration process with Lockheed Martin and help service members meet their urgent mission requirements,” says Henry Brooks, president of power and controls for Collins.
The company says the technology readiness proven by recent tests is equivalent to that required at the early stage engineering-and-manufacturing-development phase of new procurement programmes.
Notably, the Pentagon has not yet launched such a programme or even made a decision about how to address the long-term power and cooling needs of the prolific stealth fighter, which has been selected by 20 countries globally.
Upgrades to the F-35’s onboard computers and sensors – all of which require electrical power and cooling to function – have left the F-35’s single Pratt & Whitney (P&W) F135 engine operating outside its ideal tolerances. The need for extra cooling requires diverting additional bleed air from the turbofan to the PTMS, resulting in more-frequent F135 maintenance and, ultimately, earlier overhauls.
Auditors at the US Government Accountability Office (GAO) in 2023 estimated operating the F-35 in such a manner will cost the Pentagon an extra $38 billion in sustainment over the full life-cycle of the fleet.
While a separate upgrade programme for the jet’s F135 engine is under contract with P&W to address near-term power and cooling needs, the GAO review noted that the planned set of upgrades known as Block 4 will necessitate an even greater expansion.
“The addition of Block 4 will require even more cooling capacity,” the agency said in 2023.
Lockheed says Block 4 will feature improvements to the F-35’s long-range weapons systems, communications and onboard sensing capabilities, including data transmission at 5G speeds.
While the need for more electrical power and cooling is clear, how it will be provided remains nebulous.
While Collins is promising 80kW of capacity from EPACS, rival Honeywell is advancing a solution it argues will be equally effective at a lower cost.
Rather than design an entirely new system, Honeywell is pursuing an upgrade to the existing PTMS. In September, the company told FlightGlobal it was aiming to have that solution ready as soon as 2027.
“A new PTMS that is the same envelope, same interfaces, same everything, probably will not be very disruptive,” said Matt Milas, Honeywell president of defence and space technologies.
Honeywell has previously claimed that replacing the current PTMS with an entirely new solution would cost the Pentagon some $3 billion and involve retrofitting the global F-35 fleet and replacing spare parts globally.
US Air Force budget documents for fiscal year 2025 indicate the service concurs that a PTMS upgrade could be accomplished at “relatively low cost”.
Such an undertaking would involve using larger heat exchangers, shifting some systems from a cold-liquid loop to hot-liquid loop, increasing system pressure, increasing pump speeds and raising compressor discharge temperatures.
The juxtaposition of upgrading the existing system versus procuring a replacement is reminiscent of the drama that played out between engine makers P&W and GE Aerospace in recent years, with both companies vying to supply F-35 propulsion needs going forward.
P&W ultimately prevailed with an upgrade to the existing F135, which the company argued would be cheaper and faster than retrofitting the entire fleet with a new engine from GE Aerospace.
Whether that logic will prevail when it comes to power and cooling improvements remains to be seen.
In budget documents from 2024 and 2025 the US Air Force said the “existing PTMS will need to either be massively upgraded or replaced”.
“During multiple iterations of market research, it is clear that industry is capable of manufacturing a [thermal management system] that meets the F-35’s cooling and power demands,” the service says. “However, it is unclear which system will be best.”
The air force says it will continue to mature multiple potential solutions, before selecting a prime integrator based on still-to-be-determined cost, schedule and performance needs.
Additional cooling capacity is projected to be required starting around 2028 for F-35’s produced under Lot 22.
