Honeywell’s Power and Thermal Management System (PTMS) turbomachine for the F-35 remains the only operational system of its kind, with a performance track record backed by more than 1 million flight hours across nearly 1,200 F-35 aircraft delivered to the United States and allied nations.
The turbomachine incorporates advanced technologies that allow the PTMS to function as an auxiliary power unit, emergency power unit, environmental control system, and thermal management unit—seamlessly integrated into a single system.
Honeywell’s established, certified global supply network consistently manufactures and maintains the F-35 PTMS turbomachines. The 1,750th unit is scheduled for delivery this month. This resilient and dependable supply infrastructure plays a key role in the broader Defense Industrial Base, with components produced and supported in the United Kingdom, Canada, Mexico, France, the Netherlands, and the Czech Republic.
Scalable PTMS Upgrade with Minimal Risk
The PTMS remains a central component of the F-35 program’s international sustainment and industrial framework. Honeywell recognizes that all 19 global partners in the F-35 program are seeking a scalable, low-risk upgrade path for the PTMS—one that reduces the cost of development, production, retrofitting, and long-term maintenance across more than 1,156 aircraft currently on order.
To meet this need, Honeywell intends to rely on its current industrial base to reduce upgrade costs, offering a flexible solution that avoids unnecessary expenses tied to increased cooling capacity not required by all users.
Lori Schneider, Vice President, Defense Original Equipment Manufacturing, Honeywell Aerospace Technologies, commented, “Through our internal investments, we’re making great progress on a software-only upgrade to partially increase F135 engine life through reduced bleed air usage while the Engine Core Upgrade is developed and fielded. In addition to cutting engine overhaul costs, this low-risk software upgrade will increase cooling capacity 25 percent to 40kW and enable next-generation avionics upgrades by 2029.”
Honeywell is also investing in hardware enhancements aimed at expanding PTMS cooling capacity to 80kW. This increase has already been validated using F-35 digital twin simulations. These updates are structured to control cost and mitigate risk by retaining 95 percent of existing PTMS hardware, preserving current system interfaces, and safeguarding critical aircraft capabilities.
Due to the PTMS’s deep integration with F-35 systems, a complete redesign would involve significant risk and considerable expense, requiring a full-scale reintegration and retesting process to requalify 14 mission- and safety-critical functions. These include cockpit pressurization and cooling, oxygen delivery to the pilot, backup power for flight controls in the event of engine or generator failure, and ram air supply for avionics cooling during emergency landings.
Reliable Global Support for Proven PTMS
Rich DeGraff, President, Control Systems, Honeywell Aerospace Technologies, added, “Upgrading our proven PTMS is the smart choice for domestic and international taxpayers and warfighters. Our low-risk solution builds on more than $100 million in recent investments across military and commercial programs—advancements that are already flying today.
“That dual-use experience accelerates fielded capability by at least 3 years compared to a clean-sheet design and avoids costly, redundant development. We’re delivering a solution that saves over $7 billion in development, production, retrofit, and sustainment—while minimizing potential disruption to warfighter readiness and the supply base.”
Honeywell’s PTMS is supported by a globally positioned maintenance and service infrastructure. The company has worked in coordination with Lockheed Martin, the F-35 Joint Program Office, and allied nations to build PTMS repair capabilities across Europe and the Asia-Pacific region.
In 2022, Honeywell transferred turbomachine repair capabilities to Aeronamic, located at the Royal Netherlands Air Force base in Woensdrecht. A modular test cell is scheduled for delivery to Aeronamic by late 2025, which will support full post-repair testing of turbomachines.
Honeywell is also exploring further development of repair capabilities in Australia, focusing on select PTMS components to strengthen regional support.
