The future of the F-35

How an engine upgrade and better cooling would unlock the fighter jet’s true power

Since the fighter jet first took flight, the amount of cooling needed to control waste heat from its many electronic systems has doubled. And that demand will continue to grow, as officials add to the increasingly high-tech stack of sensors, jammers and other systems that make the F-35 what it is: a flying data center and command post. Or, as military officials sometimes call it, a “quarterback in the sky.”

At the moment, the future F-35’s cooling needs are out of reach. But they don’t have to be.

To make them possible, two Raytheon Technologies businesses – Pratt & Whitney and Collins Aerospace – are proposing a pair of improvements:

  • An upgraded power module for the engine that would boost performance and provide the compressed air the cooling system requires.
  • A new, optimized cooling system that uses compressed air more efficiently.

Combining those upgrades, company experts say, would give the F-35 a fast and cost-effective way to stay formidable for decades – well into the forthcoming era of even more advanced aircraft.

“The F-35 has to be not just equal to the near-peer fighter threat. It has to be superior,” said Rick “Slash” Crecelius, a former F-35 pilot and retired U.S. Navy captain who now works as a director for customer integration at Pratt & Whitney. “But technological advantage is a temporal thing. If we take too long, we start falling behind.”

Powering the F-35, now and in the future

Pratt & Whitney has proposed an upgrade to the F135 engine as part of a plan to modernize the F-35. The upgrade has several advantages, including:

Icon - Engine

a 7 percent increase in range and thrust, and an architecture that has logged more than 1 million safe flight hours

compatibility with all three F-35 variants

Icon showing an award for excellence

more than $40 billion in projected cost savings over the life of the program

Icon representing a stopwatch

a projected delivery date of 2028

Step one: Block 4 modernization

Before we get too far into the future, there’s an immediate F-35 update to consider. It’s called the Block 4 modernization effort, and it will include dozens of improvements in areas such as sensing, jamming, communications and the computer systems that underpin it all.

To put the power behind Block 4, U.S. defense officials are considering what’s known as an adaptive engine – an entirely new technology that would cost more than $6 billion to develop and take more than a decade to integrate onto the aircraft.

Engineers at Pratt & Whitney are developing an adaptive engine, but they believe it’s best suited for a new generation of fighter jets. As a faster, more affordable and more practical option for the F-35, they propose what’s known as the Engine Core Upgrade – an improved power module for the fighter jet’s current engine, the Pratt & Whitney F135.

That engine has outperformed its original specifications, having supported three major upgrades to the F-35’s airframe and payload. It has also amassed more than 600,000 safe flight hours – or 1 million, if you count the safety record of the F119 engine it was based on.

The Engine Core Upgrade boosts the original F135’s performance, including a 7 percent increase in range and thrust, through better aerodynamics and optimized cooling flows. It also keeps about two-thirds of the existing engine’s parts – a factor that makes it easier and less expensive to produce than a new engine, said Caroline Cooper, Pratt & Whitney’s senior director for F135 strategy.

“When you leverage that existing production capacity and that 60 to 70 percent commonality in parts, it’s not a hard putt,” she said. “You retrofit into the old and produce for the new.”

And while an adaptive engine would mark a major move forward in fighter jet technology, its benefits to the F-35 don’t justify the added time and expense, said Jonathan Niemeyer, chief engineer for the F135 program.

“An adaptive engine provides lots of capability, but a lot of it isn’t required based on what our customer is telling us. All those things you’re adding on, they add risk and schedule,” Niemeyer said. “If the real threat is a fight on a date that’s soon, our focus has to be on delivering mature, low-risk capability on the schedule the customer is asking for. In my heart of hearts, I believe the Engine Core Upgrade is delivering exactly that.”

A man in a sport coat and a blue button-down shirt smiles while standing in front of an aircraft engine

“Our focus has to be on delivering mature, low-risk capability ... the Engine Core Upgrade is delivering exactly that.”

Jonathan Niemeyer | Chief Engineer, F135 program | Pratt & Whitney

Step two: Block 5 and beyond

The Block 4 improvements are expected to keep the F-35 competitive for years. But given the level of investment in the aircraft by the U.S. and more than a dozen other countries – and the fact that the U.S. plans to fly it until 2070 – it’s important to think even farther into the future.

That’s where the cooling capacity comes in. The more energy-hungry, heat-intensive systems the F-35 carries, the more it will rely on its cooling system to keep them running.

“Look at how competitive the battlespace is. They want to be able to see farther, to shoot farther and more accurately. And they need the mission equipment to accomplish that,” said Henry Wu, an associate director in the Power & Controls business at Collins Aerospace. “The problem is, the cooling system they have today can’t keep up. If you buy the new radars and jammers without the cooling, you couldn’t really put them on the jet because they wouldn’t work.”

Managing the waste heat from those systems takes a good bit of energy in itself. To better serve the cooling needs of a future-state F-35, Collins has developed the Emergency Power and Cooling System – a combination of an air conditioning unit, an electric power generator and an auxiliary power unit, all packaged to fit into the current cooling system’s footprint.

A computer rendering of the Collins Aerospace Emergency Power and Cooling System

This rendering shows Collins Aerospace's Emergency Power and Cooling System, a technology the business is proposing to manage waste heat created by the many electronic systems on the F-35.

The system’s key advantage is its efficient use of what’s known as “bleed air,” or compressed air from the engine. That air is a valuable resource; the engine uses it to create thrust, and the cooling system uses it as a source of power.

But there’s only so much bleed air to go around. The more the cooling system takes in, the harder the engine has to work. And that will cause even the best of engines to wear out faster than expected.

Conversely, Wu said, more efficient use of bleed air “reduces the burden on the engine, and that means durability will go up.”

Collins’ confidence in the system comes in part because of the business’ close collaboration with Pratt & Whitney. Because both are part of Raytheon Technologies, the teams have much easier access to one another than they would otherwise. 

“If we get the ability to combine the EPACS with the Engine Core Upgrade, we can provide superior results,” said Bill Dolan, Collins’ vice president of engineering and technology for Power & Controls. “We know each other. We understand what each other does. There’s a clear advantage, if we can do these things in collaboration, for the end customer.”

Bill Dolan Vice President Power & Controls Collins Aerospace

“If we get the ability to combine the EPACS with the Engine Core Upgrade, we can provide superior results.”

Bill Dolan | Vice President, Power & Controls | Collins Aerospace

Cooling: A key to the F-35’s future

The F-35 needs a powerful cooling system to operate its growing stack of onboard technology. To meet that need far into the future, Collins Aerospace has developed the Emergency Power and Cooling System, or EPACS. Its advantages include:

more than double the cooling capacity of the current system, but within the existing footprint

icon depicting an engine

less engine wear through more efficient use of bleed air

a more efficient thermodynamic cycle

Icon showing a bar chart that increases with value over time

the ability to meet the cooling needs of Block 4 F-35s as well as future versions

The F-35’s future starts now

To Crecelius, who helped train the Navy’s first-ever F-35 pilots, the benefits of combining the F135 Engine Core Upgrade and Emergency Power and Cooling System are many.

It will save about $40 billion over the life of the program, according to a Pratt & Whitney cost analysis. It’s available not just to new F-35s but the existing fleet as well. And it would run on an established supply and maintenance network – a key concern when you need to put planes in the air at a moment’s notice.

“It wins on cost, it wins on schedule,” Crecelius said, “and it wins on performance.”

A man in a leather flight jacket gestures in front of two aircraft engines during an interview

“It wins on cost, it wins on schedule, and it wins on performance.”

Rick “Slash” Crecelius | Former F-35 pilot | Pratt & Whitney

All about the F-35

Feature story

All about the F-35

Read more