Why Upgrading the F135 Engine Core is the Smart, Strategic Choice
POLITICO | Raytheon Technologies
April 6, 2023
The U.S. Air Force has chosen to upgrade the fighter jet’s original and current engine – the Pratt & Whitney F135 – rather than develop an entirely new one.
The decision, announced as part of President Biden’s budget proposal and now under debate in Congress, “signals that the Department of Defense is laser-focused on delivering National Defense Strategy priorities, while carefully managing costs,” said Jen Latka, Pratt & Whitney’s vice president for the F135 program.
That strategy focuses on deterring attacks on the U.S., its allies and partners. Here is how upgrading the F-35’s engine – rather than developing and integrating a new one – can help.
Strength in maintaining interoperability
The F-35 program relies on international partnerships. Eight nations make up its core, and several more are procuring and flying the fifth-generation fighter jet. That results in what’s known as interoperability – a necessity in the face of new threats and conflicts on a global scale, Latka said.
“The fact that we have this international alliance and this interoperability in the air is an incredible strength and huge force multiplier,” said Latka. “That alliance is incredibly important. And the interoperability of the jet with our partners – that’s going to be the hallmark of this program when the history books are written.”
The F135 Engine Core Upgrade that Pratt & Whitney has proposed “is important to the F-35 international partners because they will field the same configuration and the same engine,” she said.
We will be ready to enter service in 2028, with meaningful capability out in the field – each service having squadrons of jets – sometime in 2030.
Jen Latka, Pratt & Whitney’s vice president for the F135 program
A targeted approach to deliver the warfighter’s needs
One of the Engine Core Upgrade’s advantages is that it would take far less time and money to integrate into the existing F-35 fleet. It is what’s known as a “drop-in” solution, meaning it requires no modifications to the airframe – and that it can use the global F135’s existing maintenance, repair, overhaul and upgrade depots.
In addition, Pratt & Whitney engineers were careful to replace only parts of the engine module – a decision that will result in a fast, cost-effective and low-risk path to Block 4 – the U.S. military’s current plan to bring the F-35 a new set of capabilities.
“What we are looking to do with the Engine Core Upgrade is keep the scope contained to the power module, which is the core of the engine,” Latka said. “The more elements you change on an engine and the more novel technology you bring in, the more risk to the program you introduce.” These targeted improvements will allow the jet to meet its power and cooling requirements, while also increasing thrust and range, resulting in lower costs and enhanced readiness.
The F135 is in full-rate production; 1,000 engines have been delivered, and production has become more efficient along the way. “We have already come down the learning curve and taken out 50 percent of the cost,” Latka said.
As a derivative of the F135, which itself is a derivative of the engine that powers the F-22 Raptor, the Engine Core Upgrade is significantly easier and less expensive to produce than a new engine. It is also “production-cost neutral,” meaning it will cost no more to make than the current engine.
“Schedule is one of the drivers in our thinking. We know that Block 4 is needed as fast as possible, and that’s what is most important,” Latka said. “We will be ready to enter service in 2028, with meaningful capability out in the field – each service having squadrons of jets – sometime in 2030. That is not how a ramp would look for a brand-new engine. It will take a long time. Building that producer base takes time.”
An imminent need for an upgrade
One unusual aspect of the F-35 program is that, nearly 10 years into its service life, it still uses the original engine configuration, despite three major upgrades to its payload and airframe.
The F135 – which both propels the F-35 and provides its electrical power – has outperformed original engine design specifications to continuously support the growing aircraft upgrades and performance demands.
“It’s really a testament to the product that this engine is managing double the [bleed air] specification while providing all the capability,” Latka said.
But now that a fourth set of upgrades is imminent, the need to modernize the engine in concert with the planned aircraft Power and Thermal Management System (PTMS) upgrades is critical.
“When we think about the roadmap for Block 4, there are more systems coming onto the F-35 – new mission systems, new weapons systems – that require more electrical power and more cooling,” Latka said. “And the engine is an enabler in both those areas.”
A smart choice for the future
Upgrading the F135 engine will save an estimated $40 billion, compared to developing and integrating the other option the U.S. Air Force considered – a technology known as the Adaptive Engine Transition Program. Pratt & Whitney is developing such an engine, known as the XA101, under a contract with the U.S. Air Force.
That type of engine, whose main advantage would be its ability to switch between fighter-jet-style flying and commercial-airliner-style cruising, will require time and money to develop – as well as a new production and maintenance infrastructure.
And that, Latka said, is part of the reason the F135 Engine Core Upgrade is a smart choice for the F-35.
“This investment is incredibly important to maintaining our nation’s technological advantage in the propulsion arena,” says Latka. “Pratt & Whitney is absolutely supportive of adaptive engines and quite proud of the one that we’ve developed and have at test right now. But rather than try to bring adaptive prototypes onto the fifth-generation F-35 jet, we believe that sixth-generation technology is best-suited for sixth-generation fighters.”