WASHINGTON — Lockheed Martin’s decision to publicly back a new next-generation engine for the F-35 — breaking with the Pentagon’s move to upgrade the fighter’s current Pratt & Whitney-made engines — drew a forceful rebuke from Pratt.
Greg Ulmer, executive vice president for aeronautics, said in a Wednesday interview with Breaking Defense at the Paris Air Show that the company supports the Adaptive Engine Transition Program for the F-35 fighter jet.
“I’m going to advocate, and I do advocate, for [AETP], another engine,” Ulmer told Breaking Defense. “I think some of the approaches today are very short sighted and not considering a longer-term view.”
In an email to Defense News, Lockheed Martin said an AETP engine would provide greater power and cooling capabilities that would carry the F-35 beyond upcoming Block 4 upgrades. Block 4 is expected to give the F-35 new sensors, the ability to carry more weapons and advanced electronic warfare capabilities, among other upgrades.
“We stand ready to support and continue to work with the U.S. government on the capability and performance upgrades that best support their requirements for the F-35 for decades to come — including an engine upgrade,” Lockheed Martin said. “AETP technologies deliver more power and greater cooling capability, which is required as we modernize the F-35 beyond Block 4.”
In a statement to Defense News, Pratt & Whitney said Ulmer’s statement “undermines” the Pentagon’s budgetary decision to back the Engine Core Upgrade, the company’s name for its plan to modernize the fighter’s current F135 engines.
“AETP is a technology that will feed into [sixth-generation] fighter platforms,” Jill Albertelli, Pratt & Whitney’s president of military engines, said in a statement. “Lockheed Martin wants to put an unproven adaptive engine on a single engine fighter jet, regardless of the hefty price tag and the significant delay in delivering critical capabilities to the warfighter at a time of urgent need.”
Albertelli noted the Pentagon has not yet defined a set of capabilities that the next set of upgrades beyond Block 4 should carry. And she said Pratt’s planned upgrade of the F135 engine, coupled with an updated power thermal management system, could provide enough power and cooling needs for the F-35 throughout the life of the program.
The F-35 is expected to fly until 2070, Lockheed said, which means further upgrades are required for the decades to come in order to stay ahead of emerging threats. An upgraded engine will be needed to provide the aircraft with greater capabilities, readiness, range and thrust, the F-35 manufacturer added.
Lockheed also noted that both General Electric Aerospace and Pratt & Whitney are developing their own AETP engines. GE’s adaptive engine is called the XA100 and Pratt’s is the XA101.
But while GE has consistently pushed for putting its adaptive engine in the F-35, Pratt maintains an adaptive engine is better suited for a sixth-generation aircraft such as the Next Generation Air Dominance platform currently under development by the U.S. Air Force.
The Air Force was intrigued by the increased power and cooling abilities an adaptive engine would bring to its F-35As over an upgrade to the existing F135 engine. But the adaptive engine’s inability to fit in an F-35B variant, flown by the Marine Corps, and questions over how suitable it would be for the Navy’s F-35C version meant the Air Force was the only service seriously interested in an adaptive engine.
The Pentagon decided the cost of funding both engine options would be too great and announced a decision to go with the Engine Core Upgrade in the fiscal 2024 budget proposal. The department did not request funding for AETP.
But the House Armed Services Committee this month proposed a version of the FY24 National Defense Authorization Act that would add more than $588 million for AETP, alongside funding the Engine Core Upgrade.
Ulmer’s comments in Paris were a departure from his previous approach to the F-35′s future propulsion system, when he opted not to pick a side.
In an interview with Defense News in September 2022, Ulmer said he was “agnostic” over whether an adaptive engine or an upgrade to the F135 was the better way to go. Ulmer said at the time that Lockheed’s role is to provide the Pentagon with information on what the F-35′s power and cooling needs will be, and that the department would ultimately make the decision.
“It’s not mine to decide, it’s the customer’s,” Ulmer had said.
Stephen Losey is the air warfare reporter for Defense News. He previously covered leadership and personnel issues at Air Force Times, and the Pentagon, special operations and air warfare at Military.com. He has traveled to the Middle East to cover U.S. Air Force operations.