The Lockheed Martin F-35 is the star of the US Air Force’s fleet of warplanes, offering the best stealth and being the most lethal, survivable, and one of the most technologically advanced fighter jets in the world.
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However, to retain its position as a super-advanced jet, the F-35 Lightning II will require further improvements than what they already have, something a new engine could provide.
The service is evaluating whether an advanced engine could offer better thrust, efficiency in cruise, superior stealth, reduction in carbon emissions than what the previous engine did. But has the USAF found a replacement for the F-35’s engines?
The three variants of the F-35 – the F-35A conventional takeoff and landing (CTOL), the F-35B short takeoff/vertical landing (STOVL), and the F-35C carrier (CV/CATOBAR)– all currently use the F135 engine developed by Pratt & Whitney.
Known as the heartbeat of the stealth jet, the engine provides more than 40,000 lbs. of thrust, unmatched low-observable signature, world-class thermal management, and the most advanced integrated engine control system delivering an unrivaled performance to 10 militaries globally.
But there is no rose without a thorn and there exists no engine that has no room for upgrades. With several reports of there being a shortage of engines, overheating and cracking of turbine blades and earlier than expected service requirements, the current F135 engines are encountering multiple issues.
This is, in turn, increasing the number of aircraft awaiting miscellaneous spare parts or are in need of upgraded F135 engine power modules and adding to the readiness issues faced by the service frequently.
Naturally, the Armed Service Committee is not satisfied with the aircraft’s sustainment and is on the lookout for an advanced engine that could deliver sizable gains in both costs as well as performance.
Adaptive Engine Transition Program
The 2022 National Defense Authorization Act (house version) requires the F-35 Joint Program Office to pursue a strategy for incorporation of the Adaptive Engine Transition Program (AETP) engine into the F-35 conventional takeoff fleet by the beginning of 2027.
The AETP is a research project by the US Air Force aiming to provide a 30% increase in range, an 18% decrease in acceleration time, and improved thermal management compared to the P&W F135 engine that currently powers the Lockheed Martin F-35 stealth fighter.
Additionally, the high-thrust mode of this adaptive engine will direct the majority of air through the engine’s core and bypass turbofan streams, delivering greater thrust for combat manoeuvering. Due to the third flow having a cooling effect, the core will run hotter further increasing the fuel efficiency.
Basically, what the USAF is looking for is re-engining the F-35A with an adaptive engine to increase the aircraft’s 2,220km range which is viewed as too short for attacking targets within China.
Options Before USAF
Pratt & Whitney, the manufacturer of the current F135 engines and is currently developing the XA101 AETP engine, has offered to make modifications to its F135 that would be sufficient to meet all the Joint Strike Fighter’s future power and thrust needs with a margin.
It argues that modifications to the F135 engine can improve thrust and efficiency and would be far less costly than giving the F-35 fighter a new powerplant developed through the Adaptive Engine Transition Program.
Equipping a combat aircraft with a new engine would add another $40 billion to the overall cost of the remaining expected 50-year life of the program, according to P&F.
GE Aviation, a rival company, has received $4 billion from the USAF to develop its XA100 engine which is in the final stages of testing. The problem that lies with the GE or even P&F rivaling to offer an engine that can fit into the F-35 fuselage and be integrated with other onboard systems is that it is designed for the air force variant and not for the marine and navy variant.
The new engines – GE’s XA100 and P&W’s XA101 – are reported to run throughout the year at Arnold AFB’s Engineering Development Complex near Tullahoma in Tennessee, according to the USAF Materiel Command.
But these new engine brings a gaping hole in the pockets of the budget of the united states compelling officials and experts to ask if the new, high-cost engines are worth the investment and R&D?
Ambiguity Over New Engines
Air Force Secretary Frank Kendall feels uncertain about the new engines saying that he favors pursuing a successor to the F135 only if it is affordable.
“If we have to, we’ll look hard at the affordability of going forward just as we have on the rest of the program. But those advantages are substantial. And I’d like to be able to pursue them if it’s affordable,” Kendall said during AFA’s Air, Space & Cyber Conference.
There are two contending issues regarding the new engines that are creating a sense of ambivalence and raising questions of viability, feasibility, and affordability.
First, since the new engine is intended to add to the newer F-35s along with the existing engines, the Air Force will have to incur huge costs maintaining two spare parts stores, two maintenance processes, and dual programs for training personnel. Second, the engine is only compatible with the Air Force variant which will be leaving the Navy and Marine services to use a separate support system.
Now, the responsibility F-35 Joint Program Office, which currently shoulders while conducting tradeoffs over the next 6-12 months, is to keep an eye on the feasibility and affordability concerns and define future options with the better range, stealth, extra thrust, and efficiency the new engine will bring in.