[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.