Forum: General F-35 Forum

arkadyrenko said: "... the F-35 has one of the most powerful engines in fighter history, and it isn't expected to exceed the speed of sound." Under what circumstances. You make an amazing claim - any evidence?

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spazinsbad - sorry, I did not fully explain myself there. What I intended to say is that the F-35 has the most powerful engine in the history of fighters, yet its CONOPs do not anticipate sustained or significant supersonic flight.

As far as I can understand the CONOPs, it will cruise subsonic at 25k ft. Above the range of MANPADs and light flak and relying on its stealth to help avoid long range SAMs. The supersonic flight will help with A2A and evading long range missiles / dashing out of trouble. This is a perfectly acceptable CONOPs, though I may have totally unsupported qualms about it, but the general idea makes plenty of sense. Why, then, does the F-35 need so much thrust? I suspect it has to do with the combination of the short body caused by the Marine variant and the internal weapon bays.

Would the F-35s ability to carry an internal weapn load with lots of fuel be a factor in having such a large engine?

arkadyrenko wrote:

spazinsbad - sorry, I did not fully explain myself there. What I intended to say is that the F-35 has the most powerful engine in the history of fighters, yet its CONOPs do not anticipate sustained or significant supersonic flight.

As far as I can understand the CONOPs, it will cruise subsonic at 25k ft. Above the range of MANPADs and light flak and relying on its stealth to help avoid long range SAMs. The supersonic flight will help with A2A and evading long range missiles / dashing out of trouble. This is a perfectly acceptable CONOPs, though I may have totally unsupported qualms about it, but the general idea makes plenty of sense. Why, then, does the F-35 need so much thrust? I suspect it has to do with the combination of the short body caused by the Marine variant and the internal weapon bays.

A design like this would doubtless get more speed out of an F135,

but that's not why it's in the F-35. All that thrust is necessary, not for speed, but to facilitate the rapid changes in energy-state required of any modern fighter design.

Doing just abit more trimming down of the excerpt yielded the following horrors of the F-35.

Is there something on this list that you could eliminate and still have a viable program? It looks to me as if everything here is really needed by the buyers. That's why it is in the requirements.
Just as a mental exercise, strike a few items off the list (to fix the program -ha ha) then re-calculate how many of the program customers would walk away. Eventually you end up with 4-5 separate development programs to build niche aircraft and the same fools would cry out at the travesty of wasteful spending. Even if you had a time machine and could sneak back to halt LMs proposal somehow -- whatever would have emerged from the JSF program would still have the same list above that that would bring some level of compromise- enough to displease many. So you would have to go back even further in time and make all the players currently involved in the program NOT WANT this list above to meet their mission goals. How do you do that.... World Peace??? It's all rather childish pointless wishing. The F-35 or something like it was probably inevitable given the boiling pot of needs that spawned it.

Lets get on with it and embrace the 'good enough' nature of the thing.

One question is: if you stretched the airframe some, could you get the bulge from the internal weapons bay / fuel fraction to decrease? But, I don't know how / if that would work.

(ps. I do hope that someone builds another high speed interceptor. We just need to invent a warfighter's reason. "Chinese bombers attacking Okinawa"?)

Archeman: how about we strike the "very short take off..." and "short air frame design," along with the partial "trade offs between agility and low weight" from the list? Get rid of the Marine variant altogether. The JSF program looses 200? 300? customers and eliminates a massive engineering challenge. Or, the JSF program could have had a technology development core, which would create the new stealth materials and avionics, mated with smaller programs to develop the specific airframes for the different services. In fact, this is already beginning to happen. The airframe commonality between the different services has declined throughout the length of the program. What is correct is that the original idea of the JSF was not successful, it has not met its original targeted specifications.

I will say that it is important to recognize the mistakes of the JSF, so that we don't make them again. For example, some commentators seem to be open to the idea of combining the F-XX USAF 6th gen program and the F/A-XX USN 6th gen program into a single joint service 6th gen program. That would just repeat the mistakes of the JSF program, as originally devised. A joint technology development program leading to two separate airframes would hopefully reduce the risk. In addition, understanding the beginnings of the JSF allows one to understand the nature of the JSF. If we know that the JSF wasn't built originally as a pure aerodynamic speed demon, then we will have to expect an A2A CONOPs that does not emphasize the JSF's performance.

arkadyrenko wrote:

Archeman: how about we strike the "very short take off..." and "short air frame design," along with the partial "trade offs between agility and low weight" from the list? Get rid of the Marine variant altogether. The JSF program looses 200? 300? customers and eliminates a massive engineering challenge.

I agree ark that if you have to make a cut to separate, that is the apparently best place to try.

So the idea here then is we tell Briton and the Marines to go off and build a separate aircraft (Briton wanted the B at the start)? We still have an additional Strike/Fighter aircraft developing program running concurrently?
I think that the thinking at the start of JSF was that the replacement of the Harrier was the most urgent item for US/Briton so we should put the engine, stealth and systems development into that project instead of into JSF so that the later JSF program (sans STOL) can borrow them. Wasn't the Navy's recapitalization and F-18 replacement also urgent? Was the plan to use the same engine in the STOL project? If we are using separate contractor groups for the two projects, how much technical information and software can be shared between the two?

Do we delay the Air Force tanker recapitalization or NGB to pay for all three projects with STOL and JSF development happening serially, or raise taxes to pay for all four concurrently?

My only point here is that splitting up the buyers to develop separate projects isn't a magic tonic that cures all ills. You just get different list of ills. Those industry folks closer to the project can probably add more to this list.

But, if you separate the different programs, then the Marines have to justify diverting x amount of their budget to the F-35B, the Navy has to justify diverting x amount of its budget to the C variant, and so on. From the USAF's perspective, dividing the programs would be the best outcome, as they have the most customers and the biggest purchase order, hence they will suffer the lease from any division.

The way technology should have been developed is this: a central program office develops the 'key technologies' for a 5th generation strike fighter. They then use those technologies in the separate airframe development programs.

And, the USAF is already putting the NGB and the tanker recap on the backburner to fund the JSF. Splitting up the programs would have the added benefit of isolating the worst cost overruns and allowing the biggest offenders to be cut. Thus, the 5th gen recap can be saved more easily at the expense of a few.

Ohhhhhh, so we separate the programs so we can delete one.
Why not just delete Marine aviation first? Then you don't have to be bothered to split the JSF and STOL programs?

Tell the Marines that they don't really need their requirements.
STOL is a silly idea that overtook them on a whim (for the last 20 years).
They can make due on whatever the Navy doesn't want - like the good ole days.

No, the Marines should justify buying the STOVL JSF using their own portion of the budget. The current structure of the JSF program puts the STOVL's problems on the back of the other services. The true cost of STOVL is hidden.

If Marine air and the Marine STOVL requirement is really worth it, then it shouldn't matter if the Marines have to build their own STOVL aircraft. Such an act would be justified by the benefits of that airplane.

ark: Thanks for the friendly banter, I just want to try to push the thrust of your point to an actionable conclusion, if that could be done.

I agree that no participant should be able to change the design so much that the other participants cannot get the aircraft that they need.
That in part was a message sent to Israel when they wanted changes as a condition of purchase.

So are we sure that because there a B model that the A and C models can't do their job?
That remains to be proven, if those A and C models pass their tests then they must be what the respective services who requested them asked for.
Like they say in politics, a vote with your nose plugged is still a vote.
I think though that what you are really talking about is trading good enough A and C models for better A and C. Unless I am mistaken in your suggestion?

Would you agree at least that the current B model, assuming it also reaches the end of it's testing in one piece, is just about the best STOVL strike aircraft the Marines could ever ask for? At least it will be the best example of the type ever built or planned anywhere anytime.
If so, then we aren't talking about the Marines being booted out of the JSF program, you are actually talking about everybody else walking out to build something else.

arkady has a 'B' in his bonnet about the 'B'. Very Happy

The F-35B is the fourth best fighter in the world now, after the F-22, F-35A, and F-35C. Delete the F-35A and F-35C, and it's still the second best fighter in the world, by a very wide margin. And while the A and C can do their jobs better than the B, neither variant can meet the B's STOVL requirement at all. Moreover, as archeman pointed out, despite the lettering order, the B was the first variant specified in the program. The program was an up-funding of the USMC aircraft to save money by meeting the needs of the other two services for less than the price of developing the other two from scratch. Plus the B wound up much better for it than the USMC could have funded alone. Developing three separate planes would've unequivocally been far more expensive than developing three variants of one.

The way to have done this on a tighter budget would have been to delete the A and C, and tell the USAF and USN they were using the USMC plane. They could add funding to it to make it better for their own uses as well, but the Harrier replacement was the most urgent and it was going to be built to meet the USMC's needs 100%. Then let the USAF and USN develop more specialized variants of it later, after the USMC plane was operational with all three services. You'd wind up with the F-35A almost exactly as it is now for almost nothing in extra development costs; replace the lift fan with a fuel tank and the 3BSM with a non-moving nozzle, strengthen a few bulkheads, and the only real difference left is which way the IPP's exhaust points. The USN probably couldn't afford the F-35C so more than a third of the program costs would be saved (C was, until SWAT, more expensive than B), but the F-35B can land on carriers, and is still a much better aircraft than their F/A-18s. The primary justification for the C is not its increased capabilities (though they are significantly increased) but that its CATOBAR flight needs then further justify the USN retaining their CATOBAR carriers against future budget cuts.

arkadyrenko wrote:

One question is: if you stretched the airframe some, could you get the bulge from the internal weapons bay / fuel fraction to decrease? But, I don't know how / if that would work.

(ps. I do hope that someone builds another high speed interceptor. We just need to invent a warfighter's reason. "Chinese bombers attacking Okinawa"?)

Archeman: how about we strike the "very short take off..." and "short air frame design," along with the partial "trade offs between agility and low weight" from the list? Get rid of the Marine variant altogether. The JSF program looses 200? 300? customers and eliminates a massive engineering challenge. Or, the JSF program could have had a technology development core, which would create the new stealth materials and avionics, mated with smaller programs to develop the specific airframes for the different services. In fact, this is already beginning to happen. The airframe commonality between the different services has declined throughout the length of the program. What is correct is that the original idea of the JSF was not successful, it has not met its original targeted specifications.

And how many jet fighter programs meet their original targeted specifications? I would say none.

At this point, the cost of these "challenges" are sunk and are not likely to affect the A or B version's development... particularly since the decoupling that occurred during last years BUR. So what you want already exists.

Furthermore you're probably not going to see any substantial changes to the F-35's structure or performance until after 2020. What you see is what you get. So suggesting you should sever the program and increase the A or C's capabilities is completely unfeasible. It would just add tens of billions in order to obtain relatively marginal performance upgrades that would not meet any objective cost benefit analysis. Furthermore it would be an act of utter idiocy for the US military to cancel the STOVL version at this stage. Suggesting that commonality is decreasing is a huge canard on your part. ITs still immense. If the commonality was purely based on avionics alone, that would more than make it worth it.

arkadyrenko wrote:

I will say that it is important to recognize the mistakes of the JSF, so that we don't make them again. For example, some commentators seem to be open to the idea of combining the F-XX USAF 6th gen program and the F/A-XX USN 6th gen program into a single joint service 6th gen program. That would just repeat the mistakes of the JSF program, as originally devised. A joint technology development program leading to two separate airframes would hopefully reduce the risk. In addition, understanding the beginnings of the JSF allows one to understand the nature of the JSF. If we know that the JSF wasn't built originally as a pure aerodynamic speed demon, then we will have to expect an A2A CONOPs that does not emphasize the JSF's performance.

This paragraph is based on a number of innacuracies, which undermine your argument. Overall we don't live in the 1960s or 70s. This is the post Goldwater-Nichols era, just as much as it is the post cold war one. Services must not operate as independent silos, and they don't. Furthermore fighter costs are increasing rapidly and developing three separate fighters, would be exorbitantly expensive.

It wasn't a mistake to combine three programs into one. Its still one of the biggest selling points with all things considered. All of the services remain huge supporters of the program. The advantages of commonality (both from an operational standpoint and a maintenance one) is huge. It would be unimaginable to develop three fighters independently that have all the capabilities of the F-35.

And the view that DoD should fund joint technology is really oblivious about the costs and development associated with this area. First off a large portion of the F-35's "ground level" technology is funded independently by the contractors and sub-contractors. These are dual use technologies that have other military or commercial applications. DoD funds the rest because firms do not find it commercially viable... so what you're asking for already exists but not in the fashion you think.

Really the main aspect of development costs emerge during the system integration phase, where they are all brought together to create a useful capability. So your suggestion would not save money, rather, it would force the military to spend more money on the most expensive part of the SDD process. You can't just make a generic avionics suite that is common to all the fighters. Its something that must be custom fitted to each design.

Starting from the top.

Archerman - the F-35B is the best STOVL fighter plane yet developed. Hands down. But, that doesn't mean that it was worth adding it to the JSF program. Having the most advanced STOVL airframe doesn't do anything, if STOVL airframes are unimportant in the era of modern conflicts. (I'm not answering that one way or another)

river_otter - that is putting airframe priorities backward. The USAF and the USN's air units are objectively more important to US national security than Marine Air. That is a fact which should have been in the minds of everyone who ran the JSF program. Once the USAF and the USN requirements and wishes are met, then we can deal with the Marines. Unless, it is determined that STOVL is a capability which is a critical national priority. A program should have its key priorities in mind. Or, putting it in other terms, the JSF program should have prioritized from the beginning.

hb_penic - Saying that few planes reach their design goals isn't the issue here. My endless problem with the B variant is that it needlessly lowered the design target, and thus eventual design completion, of the A and C variant.

But, to the future design. The problem with combining airframes is that the USAF and the USN will probably want very different aerodynamic emphasis. The USN absolutely needs more range on its carriers. USN carriers need to be able to operate outside the Chinese A2AD network and thus they'll need longer range strike and air defense. They may be willing to sacrifice aerodynamics and raw speed to achieve that goal. I don't know what the USAF is looking for in its F-22 replacement, but if its markedly different from the Navy then we get a problem again. The JSF worked, to a degree, because the USAF and the USN wanted similar aircraft: a light stealthy strike fighter. What happens if those requirements are very different? Who do we sacrifice? (If I had to guess which is more important for US national security, the USN air superiority fighter > USAF air superiority)

Here is a question: does the integration phase depend on the airframe or the avionics and sensors? That is probably changing given the different role of dispersed sensors over the airframe. And if it does, is there a way to generalize that process to make it easier? Here's a DARPA hard question. If you're right, that avionics integration with the airframe is more important, than that's going to be a problem which will call more than a little service acrimony.

Forum: General F-35 Forum

Wheeler: F-35s problems started in the Clinton Admin