Moving to replace the F-35 fighter engine is probably not affordable


Secretary of the Air Force Frank Kendall did new last week by stating in a conference speech that he was in favor of pursuing a successor to the current F-35 fighter engine “if it is affordable”.

Kendall is an exceptionally gifted public servant who holds an Aerospace Engineering degree from CalTech and a Juris Doctoris degree from Georgetown Law.

Previously, he held high-tech positions at the Pentagon, and when not in government he was active in the human rights field, often providing his legal services on a pro bono basis.

Kendall is as close to being an honest broker on technological issues as our current political culture is likely to – he is knowledgeable, objective and committed.

He sees the potential of new propulsion technologies as the Air Force has been maturing for over a decade.

But he also sees the dangers of going too far at a time when defense spending is expected to remain relatively stable.

So Kendall is probably ambivalent about a House Armed Services Committee proposal to start replacing the existing engine as early as 2027.

The F135 provides propulsion for all three variants of the fighter and is widely recognized as the most powerful and sophisticated military propulsion system in service today.

The Air Force plans to use a version of the engine on its future B-21 bomber.

The current engine has encountered readiness issues, which are at least in part attributable to the fact that spare parts and maintenance capability have been underfunded in the F-35 program compared to earlier tactical aircraft efforts.

The Armed Services Committee is not satisfied with the state of sustainment of the fighters and believes that a more advanced engine could bring significant gains in terms of cost and performance.

Performance expectations are well established: historic engine manufacturer Pratt & Whitney (a contributor to my think tank) has been competing since 2016 with General Electric Aviation to develop a next-generation engine offering 25% greater fuel efficiency and 10% greater push in a research effort called the Adaptive Engine Transition Program.

Although not necessarily intended to replace the F135 engine, the program requires competitors to offer an engine that can fit into the fuselage of the F-35 and be integrated into other on-board systems.

Both companies say testing of their respective prototypes is “on track,” without doing much else.

So, at least in principle, an alternative to F135 is in the works.

Whether it meets Kendall’s affordability test, however, is another matter.

Since its inception, the affordability of the overall effort of the F-35 fighters has been based on parts common to all three variants.

Using different versions of the same engine is a key feature of this similarity, as it allows all three reception departments to rely on the same supply chain and maintenance practices to keep their aircraft in flight.

The F-35 Joint Program bureau chief said this wouldn’t be possible if GE’s new engine was used, as it certainly won’t run on the Navy variant of the fighter and may not run on the Navy variant.

It was designed for the Air Force version of the fighter.

Thus, the Armed Services Committee’s proposal to search for a replacement engine could force the maritime services to use a different support system than the Air Force.

If Marine Services do not use the new engine, then the Air Force will have to pay all costs of developing the new engine to the point where mass production is possible.

This in itself is probably not feasible in future Air Force budgets.

But the affordability problem is even more difficult than it seems, because by the time the new engine, either GE’s or Pratt’s, becomes available, the joint force will have acquired over a thousand. of F-35 fighters.

This means that half of the Air Force fleet could end up with the existing F135 engine and the other half with its successor.

So, no matter what happens with the maritime services, the Air Force should operate parallel spare parts stores, parallel maintenance processes and parallel programs for personnel training.

The service could still be a net beneficiary given the projected gains in fuel efficiency, but that depends on what it expects the fuel to cost in the future.

This could be a net loser on the cost front.

Of course, it would still deliver performance gains with the new engine – assuming it achieves reasonable levels of productivity and reliability – and the Air Force says it needs those gains to maintain performance. propulsion of the hunter in phase with his other upgrade plans.

Needless to say, Pratt & Whitney is less enthusiastic about replacing its F135 engine than GE is; GE was repeatedly pushed back in its efforts to offer an alternative engine for what appeared to be the most ubiquitous tactical aircraft in the world until the middle of the century.

Pratt says he’s ready to offer a next-generation propulsion system, but argues that technologies from the Adaptive Engine Transition Program could be incorporated into the existing engine to deliver performance gains without a corresponding price increase.

The F-35 Joint Program Office will compromise over the next 6 to 12 months to define options for the future.

With those in hand, Secretary Kendall and his Marine Service counterpart will have to decide what makes sense.

There is no doubt that either company can develop a more advanced engine, but I bet when Kendall sees the price and considers all the uncertainties associated with integrating that engine into the force, he’ll be cold. to the eyes.

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