NATIONAL HARBOR, Md.–The F-35 Joint Program Office and RTX‘s [RTX] Pratt & Whitney have contacted
Honeywell [HON] about its Power and Thermal Management System (PTMS) for the Lockheed Martin [LMT] F-35, but no substantive discussions about upgrading the existing PTMS are underway, as the F-35 JPO analyzes the future thermal requirements for the F-35 and the best path to hit those requirements, a Honeywell official said this week.
Pratt & Whitney said that it has established firewalls between its F135 Engine Core Upgrade (ECU) and the Enhanced Power and Cooling System (EPACS) design effort by another RTX subsidiary, Collins Aerospace, for a new F-35 PTMS (Defense Daily, Aug. 16). PTMS is under Lockheed Martin’s F-35 airframe purview, while ECU is under Pratt & Whitney’s responsibility for the F135 engine, and thus Honeywell needs special dispensation from the F-35 JPO to hold talks with Pratt & Whitney, F-35 program and Pratt & Whitney officials have said.
“It’s been pretty quiet as far as them sharing any additional information on the ECU, which is a bit disappointing because we are ready to go with the technology roadmap that gets us to 60 to 80 kilowatts of cooling capability–double to triple the cooling capacity of what we’re doing right now, and we have a high TRL [Technology Readiness Level] path to get there,” Matt Milas, president of Honeywell’s defense and space business, said in an interview at the Air and Space Force Association’s air, space, and cyber conference.
“One of the key features is we’re ready to go now, while the ECU timeline is right now,” he said. “If we wait to develop some sort of new power and thermal management type of solution, that’s years out of…the ECU timeframe so we’re gonna be disjointed once again between the engine and the airframe.”
Honeywell’s Torrance, Calif., plant builds the F-35 PTMS, which supplies main engine start and auxiliary and emergency power needs, in addition to 30 Kilowatts of aircraft cooling, but the F-35 JPO and industry representatives say that the current PTMS needs an upgrade or replacement to accommodate the cooling requirements of new weapons and sensors for Block 5 of the F-35, which is to field after 2030, and possibly for Block 4.
“The JPO is in the early stages of determining next steps for PTMS modernization,” Jen Latka, Pratt & Whitney’s vice president of F135 programs, wrote in an email last month through Pratt & Whitney public affairs. “We will support them in their efforts as required. The JPO asked us [in] mid-June 2023 not to share any information on ECU with potential PTMS providers because it could turn into a competitive effort. Based on this request, Pratt immediately developed and implemented a mitigation plan that includes firewalls between our Pratt ECU and Collins EPACS teams to avoid conflicts of interest. We respect the JPO’s desire for a fair competition on PTMS.”
Collins Aerospace said at June’s Paris air show that the company had conducted a lab test in Windsor Locks, Conn., of the EPACS (Defense Daily, June 28). Collins Aerospace said that EPACS will provide “more than twice the current cooling capability to support additional growth beyond Block 4 and is expected to provide enough cooling capacity for the life of the aircraft.”
EPACS includes a Collins Aerospace air cycle system, electric power generator and controller and an auxiliary power unit (APU) by Pratt & Whitney. The F-35 now has Honeywell’s GTS130 APU.
Jill Albertelli, president of Pratt & Whitney’s military engine business, has said that “the F135 ECU paired with an upgraded PTMS can provide 80KW [kilowatts] or more of cooling power for the F-35, which will exceed all power and cooling needs for the F-35 through the life of the program.”
Honeywell said last month that it has been working with Lockheed Martin and the F-35 JPO to lend up to 17 kilowatts more of cooling for the F-35 for a total of 47 kilowatts of cooling on the Block 4 F-35.
The addition of 17 kilowatts of cooling includes two kilowatts to be fielded in PTMS next year under the F-35 Continuous Capability Development and Delivery effort. The two kilowatt improvements include “optimizing the cold liquid loop architecture and increasing the ability to use the jet’s heat sinks via the thermodynamic cycle,” Honeywell said.
From Honeywell’s standpoint, the 17 extra kilowatts may be enough extra cooling for the sensors and weapons on F-35 Block 4, while Block 5 after 2030 will likely require additional incremental changes like additive or other advanced heat exchangers to give the fighter 60 kilowatts to 80 kilowatts of cooling. The requirements for Block 4 and Block 5 thus far are not firm.
In May, a Government Accountability Office (GAO) report highlighted a lack of bleed air from the F135 and said that the F-35 will need a new or improved PTMS to accommodate future weapons and sensors on the aircraft (Defense Daily, May 30). The question appears to be when.
“The way we’re designing the PTMS upgrade you don’t need any additional bleed,” Milas said this week. “We’re designing with the current F135 [engine] in mind because we don’t have the ECU data. We found a way to reduce the amount of bleed required by turning on the combustion mode of the APU that’s part of the PTMS system so you can decrease the amount of bleed which reduces the stress on the engine, but also provides a higher level of cooling capability.”
Milas has said that replacing, rather than upgrading, the existing F-35 PTMS, which is integrated in the F-35’s electrical and life support systems, is like “doing heart surgery” and that a new PTMS could cost $3 billion (Defense Daily, Aug. 14).
Pratt & Whitney and Collins Aerospace declined this week to comment on PTMS beyond what they had already said.