WASHINGTON — As the Defense Department starts to put money toward advancements that will keep the F-35 relevant against Chinese threats, incumbent engine manufacturer Pratt & Whitney is making the argument that F135 propulsion system upgrades should be part of the equation.

Over the next decade, the Pentagon is set to upgrade the Lockheed Martin-made F-35 with a suite of new weapons, computing technologies and software that will make the jet a more capable foe, as Russia and China field their own improvements to fighters and air defense systems.

But F135 engine modernization is not included in those Block 4 upgrades — at least not currently, said Jen Latka, Pratt & Whitney’s vice president for the F135 engine program.

“Now is the time we need to get the requirement in place, the funding, and then start the program,” she told Defense News in an Aug. 6 interview.

In March, Pratt & Whitney delivered a study to the F-35 Joint Program Office on F135 engine upgrades, which proposed two enhanced engine packages, which could be applied to all three variants of the F-35.

“Our objective was to provide the most cost-effective solution we could identify to meet the future requirements on the air vehicle,” Latka said.

The F-35 joint program office told Defense News in a statement that it is evaluating the Pratt & Whitney study “and data from other sources as we assess future power, cooling, and air vehicle performances needs of F-35 beyond Block 4.”

The company believes that an enhanced engine would provide an 11 percent improvement in range, 10 percent improvement in thrust and a 50 percent increase in thermal management — an important factor for enabling the F-35 to retain its stealth characteristics.

While Latka declined to detail the development and non-recurring engineering costs of proposed upgrades, they are designed to be “production cost neutral” — meaning that once the improvements are spliced into the production line, the Pentagon will be able to buy advanced F135s at the same price as the older model.

The upgrades are also designed around making the engine less expensive to sustain. An enhanced engine could generate approximately $40 billion in sustainment savings over the life of the program, according to Pratt & Whitney estimates.

The F135 is already being operated in excess of its specifications as new capabilities have been added to the F-35, Latka said.

That is only going to become more of a problem as the Pentagon upgrades the F-35 with Technology Refresh 3 — a new core processor, memory unit and panoramic cockpit display — and adds the Block 4 hardware and software capabilities, which will further tax the jet’s existing weight and cooling thresholds.

“[The services] have a very ambitious modernization program,” Latka said. “They’re going to continue to put capabilities on that jet. And so we need a requirement in propulsion that is commensurate to support … the added weight [and] all the performance requirements that come with adding capability.”

Lt. Gen. Eric Fick, the Pentagon’s F-35 program executive, has previously acknowledged that the F-35 engine will likely need increased power and thermal management to accommodate Block 4 technologies.

“I think the need to look for options from a propulsion system perspective is present,” he told lawmakers during a July 13 hearing.

However, it’s unclear whether the Defense Department will seek to upgrade the existing F135 design or move toward a brand-new propulsion system. The Air Force is currently testing three-stream adaptive engine prototypes made by Pratt & Whitney and General Electric as part of the Adaptive Engine Transition Program.

Fick saw GE’s engine prototype while visiting the company’s facility in Evendale, Ohio, earlier this summer.

“Candidly, I was impressed,” Fick said, adding that while “there’s a lot of work to be done before that becomes a production engine, before that becomes a reality for the F-35 program perhaps,” he would work with the services to explore alternative engine options.

While the F135 meets the Air Force’s current requirements, the service will have tested and garnered data from prototype AETP engines by the end of FY22, which will help inform future F135 upgrades, Air Force acquisition executive Darlene Costello said during the hearing.

Lt. Gen. David Nahom, the service’s deputy chief of staff for plans and programs, told lawmakers that the service is “very excited” about the increased power and efficiency the AETP engines could bring to the F-35. However, fielding it would require a “significant investment” that is not currently part of Air Force budget plans.

“Right now, given the current top-line we have right now, we’re going to struggle to get any further with this technology,” he said.

Brig. Gen. Dale White, who leads the Air Force’s program office for advanced aircraft, poured even more cold water on the idea of upgrading the F135 with AETP technologies during a Aug. 12 roundtable with reporters.

“The technology that is inside AETP is very different than what we use on the fielded systems we have,” he said. “And so trying to change a power plant in … a fielded system is extremely complex, and there’s a lot that goes with that. And so you have to think about what the return on the investment might be there.”

Valerie Insinna is Defense News' air warfare reporter. She previously worked the Navy/congressional beats for Defense Daily, which followed almost three years as a staff writer for National Defense Magazine. Prior to that, she worked as an editorial assistant for the Tokyo Shimbun’s Washington bureau.

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