[cpgxiii]

This whole "multi-service aircraft can't work" meme has been going for essentially a century, and has been wrong just as long.

The F-4 Phantom, probably deserving the title of greatest Western multi-role aircraft of the cold war, had long successful service with both USAF and USN (and USMC), with fewer inter-service airframe differences than between the F-35A and F-35C. Multi-service aircraft are totally workable, the services just don't like having to play nice with each other.

The F-35 is better thought of as a family of tightly-related aircraft which share as many major systems as possible (avionics, sensors, engine, cockpit) while having differing airframes. Doing exactly the kind of reusable engineering a major project should be doing. You can claim that different project management might have been cheaper, but the idea that three separate airplanes, one for each service, could have been engineered and produced for less is just wishful thinking.

[indymike]

> This whole "multi-service aircraft can't work" meme has been going for essentially a century, and has been wrong just as long.

I'm not sure that's really the case. When we see successful cross-service adoption, it's because the aircraft simply was that so good the other branch saw a lot of value in buying it. So far the only program that has worked from inception is the F-35. The others failed to get traction in the other service (F-111, F-16). What all other aircraft that have crossed services have in common is iterative design resulting in a superior aircraft:

Air Force to Navy

- F-86 Sabre designed for Air Force, Navy adopted it as FJ2 Fury (straight wing) and FJ3 Fury (swept wing version of FJ2). The FJ3 was a counter to the MIG-15 and was a navalized F-86. It's performance was superior at the time.

Navy to Air Force

- F-4 Phantom II. Naval multi-role fighter was just that good... better than most mission-specialized Air Force fighters at their own missions. Iterative design from the McDonnel F3H Demon that borrowed some ideas from the Douglass F5D Skyray.

- A-7 Corsair II. Naval attack aircraft. It's primary value was that it was inexpensive to operate and hit a sweet spot for payload and range. Iterative design from F-8 Crusader (which was probably the best air superiority fighter of it's era).

[cpgxiii]

My point is that multi-service aircraft are entirely possible, and have been all along. That several notable aircraft emerged as multi-service aircraft is all the more evidence that a multi-service aircraft (really, a family of tightly related aircraft) can be designed as such. The reason there are more USN->USAF success stories is that it is much easier to design an aircraft with the stresses of carrier operation in mind than it is to navalize a entirely ground-based design, and it is much easier for the USN to make the case politically that a USAF aircraft "can't possibly meet their requirements" than the reverse.

The USAF and USN are just incredibly unwilling to have to compromise to work with each other, and for most of the cold war had the budgets and supplier diversity to acquire entirely separately.

[indymike]

> The USAF and USN are just incredibly unwilling to have to compromise

I don't think that is the case. The issue is that most of the joint programs fail because they start with such a broad difference in requirements the program can't work. Here are two examples:

F-111/TFX - Navy wanted a fleet interceptor / air superiority fighter built around the Phoenix Missile. Air Force wanted a heavy attack aircraft. The F-111 led to the Navy having to do a crash development to get the F-14 Tomcat.

F-16 LWF - Navy wanted a twin engine. AF wanted single engine. Joint program died immediately... so we the taxpayers ended up with the USAF buying F-16 (great aircraft) and the Navy ordering an update on the YF-17 which became the F/A-18 Hornet (another great aircraft). Incidentally, the YF-17 was a twin engine iteration of the F-5 (which is an iteration of the T-38 Talon), and the F/A-18 is an iteration of the YF-17.

> for most of the cold war had the budgets and supplier diversity to acquire entirely separately.

I think you are on to something: lack of supplier diversity will be a forcing function in the future...

[cpgxiii]

> The issue is that most of the joint programs fail because they start with such a broad difference in requirements the program can't work.

Agreeing on requirements is the most important compromise. You can always come up with different requirements that make collaboration impossible. Sometimes these differing requirements are fundamental - e.g. the E-2 and E-3 (E-7 in the future), while performing similar roles, are necessarily very different platforms - that a joint program would never be considered. Sometimes these requirements are not so fundamental - e.g. the many years of single-engine versus twin-engine disagreement - that a joint program is possible, albeit challenging.

While the JSF program has had plenty of issues, the fact that it has been successful in delivering the envisioned aircraft is a testament to (a) technology improving to the point that many once-dealbreaker requirements (e.g. single-engine) could be swept aside, (b) the rise in costs making it clear that completely separate development programs were impractical, and (c) explicitly providing requirements flexibility via the "family-of-aircraft" approach (no way the F-35C would have been acceptable financially to anyone other than the USN, no way the F-35A would have been suitable for carrier use).

> ...lack of supplier diversity will be a forcing function in the future...

The consolidation of the 90s and 2000s is directly the consequence of lower budgets. Consider the fighter/strike fleets of the 1980s:

- USAF: A-7 (LTV), A-10 (FR), F-4 (MD), F-15 (MD), F-16 (GD), F-111 (GD), F-117 (Lockheed)

- USN: A-6 (Grumman), A-7 (LTV), F-4 (MD), F-14 (Grumman), F/A-18 (MD)

versus today:

- USAF: A-10 (none), F-15 (Boeing), F-15E (Boeing), F-16 (LM), F-22 (LM), F-35A (LM)

- USN: F/A-18E/F (Boeing), F-35C (LM)

there's just not enough business to support much more than the Boeing/LM duopoly keeping both production/support running and enough capability to be competitive for the NGAD programs.

[coredog64]

I generally agree with your thesis, but:

The F-4 was built for the Navy and the other services saw what a great plane it was and bought in.

The F-35 is intended as a lightweight multi role aircraft, so it’s full of compromises already.

The F-111A/B as a shared USAF/USN aircraft is much harder as there’s not as much margin for compromise in something that is supposed to be the pinnacle of current performance.

[cpgxiii]

I'd say the F-111 is a particularly odd case, given the vastly different initial requirements involved. To be clear, everything that made the F-111 a great long-range interdictor for the USAF would have have also made for a great long-range interceptor and strike platform for the USN. It wouldn't have made a good air superiority fighter, and the experience over Vietnam made it clear that this capability was still very much necessary, and there was nowhere near enough budget (or, more critically, carrier deck and hangar space) for the USN to operate both an air superiority fighter and a dedicated long-range interceptor.

There is a very long list of could-have-been multi-service aircraft, though. If you look at the number of ground-based operators of the F-18, clearly the USAF could have been satisfied with it as well. The USN probably could have been satisfied by a navalized F-22 derivative (the story of 1990s/early 2000s procurement is complicated), the USMC definitely could have been satisfied by a navalized AH-64 rather than developing the AH-1Z, etc.

The services are just very resistant to ever needing to compromise on procurement issues unless Congress and the DoD make it clear that they have to. The USN feels their needs are special, and that the USAF would dominate any shared procurement and force them to compromise too much, while the USAF feels like every pound added for carrier operation is a direct affront. Neither view is entirely wrong - the development delays and compromises of a navalized platform like the Dassault Rafale are another good example of the costs of shared development - but the simple reality of modern aircraft development costs and defense budgets means joint platforms are here to stay.

[greedo]

The USN didn't need an air-superiority fighter when they were working on the F-111B, they needed a fleet defense fighter capable of lifting a huge radar and missile set. When the terrible engines in the B model gave them an out, they took it and moved forward with the Tomcat (which used the same engines and weapons set). Little did they realize the TF-30 would remain a terrible engine for so long, and replacing it with F110s would take almost two decades.

I'm not sure that the F-22 would have ever worked for the USN either. I think that its stealth coating are just too fragile for a marine environment. And the USMC could never afford the AH-64.

[cpgxiii]

The engines certainly gave the USN the out it wanted, but the thing that truly killed the F-111B was the need for a dogfight-capable fleet fighter. There was no way they could have afforded two separate fighter development programs at the time, and Grumman had just the design they wanted ready to jump to.

The NATF program probably would have worked out fine, albeit expensively. There has always been speculation that part of the selection of the F-22 over the F-23 was because the F-22 was considered more suitable for a navalized version - and the comparatively small design differences between the F-35A and F-35C designed later by the same group suggest that a similar amount of work would have been involved in navalizing the F-22. Coatings would have been an issue in the 90s, but would largely have been solved by an realistic service entry date in the late 2000s. What killed the NATF was post-cold war budget reductions and shortsighted policymakers, not technical challenges.

The story of a navalized AH-64 is an equally strange saga. To hear the USN and USMC tell it, you would think it impossible to operate the AH-64 from a ship, yet the RN has done so extensively with relatively minimal modifications to the airframe. Given the small production run of the AH-1Z/UH-1Y program, it's questionable if much was saved. Certainly if you look at foreign customers, the capability/price of the AH-64 has been much more appealing than the AH-1Z.

[greedo]

Regarding the Sea Apache, it really would have been a huge redesign. Deleting the 30mm Chain Gun, moving the landing gear to the wing stubs, adding a nose mounted radar, and Harpoon/Sidewinder capability. Now some of these requirements were Navy specific, but some would have been required had it been selected just for the USMC.

I think that even an unmodified Apache would have been just too expensive for the always cash-strapped Corps. Plus the airframe and engine commonality with the UH1s they flew simplified their logistics tremendously. It's always a gamble comparing unit costs since so much is either hidden or excluded, but the latest info I found showed a new build AH-1Z was around $30M in 2018, while a new build AH-64 is currently around $52M. And I'm pretty sure the Corp has simply been rebuilding older airframes to the new "Viper" standard. (Turns out most were rebuilds, but some were new construction.)

Regarding the RN flying Apaches, is this from large decked ships, or from anything with a pad? I know the Merlin had a neat winch type thing to help it land in bad weather, and I just wonder how much more likely a rollover would be on a small decked ship versus something like HMS Ocean etc.

[cpgxiii]

I think the Sea Apache design was doomed to failure, potentially deliberately, by including so many modifications to the base design. A reasonably scoped modification for the USMC would have been the standard increased corrosion resistance, folding main rotor, tail wheel moved forwards, and folding tail fin+rotor (i.e. all the same modifications made to the base S-70 design for shipboard use).

The cost question is a very tricky one, hence why I used the comparison of foreign orders between the two types as an assessment of overall value. My understanding is that more AH-1Z/UH-1Y airframes were new builds than was originally planned (hardly a surprise), which strongly suggests that airframe reuse did not save as much in production as hoped. The strongest argument for the AH-1Z cost-wise was the commonality with UH-1Y, but had the USMC considered switching entirely to AH-64 + SH-60 derivatives instead I don't think that argument would have been as strong (after all, the whole rest of the USN operates SH-60 variants, including the ships that operate USMC AH-1/UH-1s).

The RN has flown WAH-64s from their large deck ships, so roughly equivalent size-wise to anything that routinely operates AH-1Zs. The only important modification in the WAH-64 design is a folding rotor to reduce storage size, but that doesn't affect takeoff/landing abilities. With some minor changes like pulling the tail gear forwards (e.g. as on the {S,M}H-60{B,F,R}), you could fit an Apache on anything that can handle a Seahawk (i.e. basically everything with a pad). Notably, the AH-64 wheelbase is not that different from the spacing of the skids on an AH-1, so it's not going to be hugely different in terms of stability on a large deck ship. There's also been a fair number of training exercises between US army AH-64 units and USN ships, so shipboard Apache operations aren't exactly foreign to the US either.