Thanks to a newly created “digital twin” of the Pratt & Whitney F119 turbofan, a future software update for the Lockheed Martin F-22 will expand the kinematic performance in certain regions of the twin-engine stealth fighter’s flight envelope.

As digital engineering tools proliferate through the aerospace supply chain, operators and OEMs have touted benefits such as streamlining maintenance activity and refining the data used to inform new engines and aircraft as they are being designed.

• F119 engine upgrade validated in wind tunnel
• Velocity, acceleration rates improved

But the pending F-22 upgrade may show that creating and analyzing digital copies of physical parts can yield unexpected performance improvements at the midlife stage in the operational career of a combat aircraft.

Specifically, Pratt executives started collecting data on the usage history of individual F119s in 2018. As terabytes of data from real flights were analyzed, Pratt found that operators used the engine differently than the F119’s designers had assumed when calculating how long the parts could last until they needed to be replaced. In some areas of the engine, such as the core and low-pressure module, real flight hour data showed that the parts could last up to 20% longer than the company had predicted. The front fan also was more robust than expected, but not by the same margin.

Knowing that the engine’s parts could last longer than expected, Pratt gave the U.S. Air Force options. They could continue running the engines as they have been doing, and capture more than $800 million in cost savings over the aircraft’s lifetime by deferring the replacement of certain parts. Alternatively, the Air Force could use some of that additional strength in the part and extract more engine performance.

“You realize you have margin that you could potentially spend without a negative detriment, then that opens up the ability to expand the capability of the engine,” Scott Ackroyd, the F119 chief engineer from Pratt & Whitney, tells Aviation Week in an interview.

As an engine produces additional thrust or acceleration, the parts are sometimes exposed to higher temperatures. Since the data from Pratt’s digital twin of the F119 shows that the parts are more robust than intended, operators can expose those components to hotter temperatures without paying more for maintenance later. In this sense, the operator trades more performance in some areas of the flight envelope for long-term cost savings from operating normally and deferring maintenance.

Pratt’s software engineers revised the software code for the F119’s digital electronic engine control (DEEC), a computer that schedules and maintains the operating point of an engine by regulating conditions such as rotor speed and nozzle throat area.

“We changed the order of how we control the parameters inside the envelope to provide more capability and kinematics and certain regions,” Ackroyd says.

Using agile software development methods, Pratt delivered the DEEC software update in nine months, including regression testing and 100 hr. of engine testing in a wind tunnel. Pratt has now turned the new software over to Lockheed, which plans to include the engine performance upgrade in a future update of the F-22’s operational flight program.

Pratt cannot disclose the details of the performance improvement, citing Air Force security restrictions. The maximum continuous thrust rating of about 35,000 lb. for the F119 will not change after the software update, but kinematic performance—meaning, velocity and acceleration—will be improved in certain areas. The Air Force wants to improve performance in a specific area of the existing flight envelope for the F-22, and the tweaks made to the F119 control software enabled Pratt to make that change.

“We were lucky that they lined up exactly where they wanted,” Ackroyd says.

The use of digital twins may spread beyond the F119, but there are limits. For example, Pratt introduced a DEEC in a fighter engine with the F100-PW-229, but the decades-old processor would have to be upgraded to run the algorithms that deliver the improved performance in the F119. Pratt also is working to perform the same usage life analysis on the F135 engine that powers the Lockheed Martin F-35, which would be based on creating a digital twin of existing engines now in service.