On Dec. 13, 2023, Maj. Kristin “Beo” Wolfe pilots an F-35 Joint Strike Fighter during training at Hill Air Force Base in Utah.

Due to an additional degree of assessment added by the government, the F-35 fighter jet’s engine upgrade is scheduled for many months beyond first planned.

A representative of Pratt & Whitney, the RTX-owned business that produces the F135 engines for the jet, informed reporters on Tuesday that the initial design review for the Engine Core Upgrade program is scheduled until May 2024.

That is more than the firm had anticipated when it announced in the fall of last year that the evaluation would take place in January 2024, around one month after the company anticipated finishing its preliminary design.

The F-35 Joint Program Office stated in a statement to Defense News on Friday that the design review is “event driven” and has not been postponed, but it is examining the engine improvement in more detail.

The JPO stated, “We have extended the timeline to include a senior-level engineering and technical review, which is scheduled for February/March.” “As we go toward the PDR [preliminary design review], the JPO and our industry partner Pratt & Whitney continue to decrease risk.”

Heather Uberuaga, a spokeswoman for Pratt & Whitney, stated that the Engine Core Upgrade program, or ECU, is proceeding as planned and directed any further inquiries to the JPO.

The goal of the initiative is to increase the F-35’s thrust, power, and cooling capacity. This is required for a broad range of planned Block 4 fighter modernizations that would increase the aircraft’s weaponry capacity and enhance its sensors, targeting, and electronic warfare capabilities.

The F-35’s present Pratt & Whitney F135 engines are still in use, but last year the Pentagon upgraded them rather than designing a whole new engine to give the aircraft the thrust, power, and cooling capability it needs.

Pratt’s vice president for the F135 program, Jen Latka, also said reporters that the firm is on schedule to complete the engine upgrade’s design by the middle of 2025 and begin testing it the following year. Next year is anticipated to see the completion of the ECU’s critical design assessment as well.

According to Latka, this will enable the engine update to be delivered in 2029.

Executives at Pratt & Whitney have played down the risk of a prolonged continuing resolution on the long-term schedule of the ECU program. Air Force Lt. Gen. Michael Schmidt, the program’s chief executive, alerted legislators in December that if a 2024 budget isn’t approved, money for the engine improvements may run out in a matter of months.

Latka informed reporters that an extended continuing resolution for a longer duration would have an impact on ECU and other programs, as approving a budget is essential. She did, however, note that it is doubtful that a longer ongoing settlement will cause the 2029 engine modifications to be launched later than planned.

According to Latka, “a lot of different design pieces are progressing at different rates right now.” “The exact day the money runs out and the timer goes off is unknown to us.”

According to Latka, the F-35B variant’s configuration will be different, but all variants of the fighter, including the “B” model with a tilting engine that allows the fighter to hover, will fundamentally employ the same core improvement.

According to Pratt & Whitney, it will take around 18 months to replace the engine cores in every F-35 that is currently in service. According to Latka, the military’s own maintainers could install the new engine core in a few shifts at depots or maybe on the flight line once it is ready.

Latka said, “It’s a fairly simple exercise, but it’s not a one-shift job.”

According to Latka, Pratt & Whitney is primarily utilizing digital design methodologies for the F135 modifications, which should increase the quality of the engine’s componentry while also saving time and money. She stated that all pieces are being designed by the company using a computer model, and when the digital blueprints are completed, the company will submit them to suppliers for construction.

The entire “digital thread” for every component will benefit in the military services’ preventative maintenance programs, according to Latka. She also mentioned that Pratt & Whitney’s proposal for a next-generation adaptive propulsion engine will likewise employ a totally digital procedure.

Pratt & Whitney’s president of military engines, Jill Albertelli, also mentioned the company’s intention to test prototypes of its next-generation adaptive propulsion engine in the late 2020s. This engine would be used in the Air Force’s Next Generation Air Dominance fighter.