The UK has a a substantial industrial base on its own, like most of Europe they have to count pennies yes.
But Germany and France have there own budget issues.
yes they do but then again the UK has in the past operated its own capabilities and still sits near the top of the list easily #3 Italy #4 Spain is civil aviation their military is no where to be found. They buy from everyone else and in small numbers. That military capabilities they had were sold off to Airbus
Not to long ago the German army was issuing painted broom sticks to training units to stand in for machine gun barrels that they couldn't afford.
France right now is in financial trouble and has been enacting Austerity measures this most visibly took the form of the yellow vests riots.
Germany and France however created this fighter and tank program in a move to centralize European military power and R&D between Germany and France. Who in many ways already centralized the EU power base into a Franco-Gemanic Empire.
This move might face kick back from EU and NATO states who prefer there own industrial bases and prefer not to take orders from Berlin or Paris.
Increasingly the Eastern NATO states those who peeled off the former Warsaw pact have been placing pressure to get more power and there interests and voices heard.
We can see this in the Russia divide. Where Germany is pro Russian investment and Poland and the Eastern states don't want Russian interests ahead of there own.
The UK also seems to have been on a similar mind to this and traditionally has maintained there own military industrial complex and maintained only observer status in the EU to hold some measure of its own statehood. Even beyond that The UK exports more to the EU than the EU does to the UK.
Worst comes to worst the fall back for the UK and Italy Tempest doesn't automatically fall to the FCAS it could still go to the US F/A-XX which is more multi role and more inline with the Objectives laid out (vs F-X) Remember the US and UK have a tighter relationship than most mil to mils sometimes tighter than the US-Canada relationship and we are joined to them at the hip.
When either the British or US has a new military technology not even nessisarily ready for export one of the first partner offers goes to the other. Cobham armor on the Abrams, President Reagan's offer of F117, And the JSF partnership where as much as the USAF or USMC the Brits were given a seat at the table for F35B. X35B and X32B were flown by British pilots no other partner had that.
Like I said here before Italy has Leonardo. So they have their own military-industrial capabilities. Read my prior post for more details.
It is easy for someone who does not know about the Italian aerospace sector to underestimate their capabilities.
Spain (ex-CASA now Airbus Military) mainly manufactures turboprop military transport aircraft.
For example they manufacture the C-295 aircraft. It is a decent aircraft in its segment with a lot of foreign customers.
The Spanish also have licenses to manufacture a couple of army weapons systems. Their naval military industrial sector is probably the most advanced of the three branches.
If they cooperated in a fighter program they could probably only work on manufacturing fuselages or doing software work.
If for whatever reason Airbus Military in Spain could not participate their collaboration would probably be restricted to software work.
France is having economic issues, yes, but their industry can do a fighter program. It is a matter of national will to do it.
They dominate all aspects of the required military-industrial domain knowledge.
Germany simply lacks the domain knowledge of too many requisite military technologies to do their own program.
People really overestimate their capabilities. They are good at some weapon systems like small arms, armored vehicles, and diesel-electric submarines but that is it.
At least the Germans could not do it without either substantial expense and a protracted development period and/or purchasing major components abroad.
They have some know-how in materials technologies. So they could aid with the fabrication of engine components. But they can't design an engine by themselves.
They have aerospace R&D centers which could help with airframe design but little practical experience in actual combat aircraft design. So I think there would be a high chance of them flopping if they had to design an airframe. Their airframe manufacturing facilities are IMHO less advanced than the Italians. Believe it or not.
Heck I would rather be in a fighter program with the Swedes than the Germans if know-how was the issue rather than selling planes.
The UK has other possible partners if they look outside the usual places. South Korea and Japan for example have their own stealth aircraft programs.
Japan could make contributions in basically any sector of the design. South Korean expertise is more limited although they have a really robust civilian sector which they have proven more than once in the past is able to easily contribute to advanced and complex military programs. Particularly in electronics.
There is also Turkey but it would likely run into issues with US export controls and their economy is a bit chaotic. It is unlikely they could make major design contributions but they can do some limited fabrication.
There are a lot of possible clients for these aircraft if, for whatever reason, the US denies the sale of stealth aircraft to the Gulf states.
But I would not rely on it.
Poland has a right-winged government right now which is breaking EU treaty obligations. Same situation applies to Hungary. I think it is extremely likely that they will both get their EU council voting rights suspended in the middle term. I know they currently have grid-locked this decision
But I think it is not impossible to do it if Germany and France really push for it.
I think all it requires is some, uh, creative interpretation of the EU treaties to break the gridlock.
The current government of Poland made leaving the EU part of their campaign platform. So we might see a Pl-exit, and even a Hu-exit soon.
The situation in Italy is also sketchy at best but the Italians always wag their tail at the Germans so they will probably remain unless they are kicked out.
Do not count on a significant UK participation on a joint US program. The UK expended a not insignificant amount of resources on the F-35 program and I see little that justifies it so far. It might even happen that the UK simply buys more F-35 planes and skips this project altogether. I am not kidding.
There are precedents for this like the TSR-2 cancellation and the failed F-111 purchase. I think it would be a big mistake for the UK not to have a long distance strike platform however and the F/A-XX is simply too far away in time for it to be relevant I think. The F-15X purchase also makes the possibility of a US fighter program being accelerated doubtful I think. Between that and the F-35C I think the other fighter programs will run at a snail's pace.
The UK already has the engine work they made with GE for the ATF program and the alternative engine for the F-35.
From what I understand the program is at a high technological readiness level and is more advanced than the current engines the US operates.
The Italians already have the radar technology. It would take little effort to do it.
The UK already seems to have decided on an airframe design. The only question is will be Italians be interested in that kind of program.
What is it to be? An interceptor? A long distance reconnaissance and bombing platform?
If it was me I would design it as an interceptor and add the bombing capabilities later.
The Franco/German program is way too different for it to be folded into the UK/Italian program. Because those countries will not purchase the F-35.
So understand that they will have totally different design requirements. That's why I think participating with Japan would be a better idea.