Aside from coding, what prevents American fighters from firing foreign missiles (and vice versa?)

AIUI, the reason that fighters of a certain nationality (i.e., American) typically cannot carry or fire foreign missiles (i.e., Russian, French or Israeli) is because of 1) the coding or programming is incompatible and 2) the weapons pylons might not be compatible for loading the weapon aboard (wouldn’t fit in the ports/whatever-they-are-called.) What other reasons are there?

Well, I daresay if you’ve got hardware and software incompatibility, everything else is kind of moot. I suppose you could add to that the complexity of the training of ordnance loaders (pdf file on loading/unloading procedures for Navy and Marine airborne weapons crews) where they must follow specific checklists and procedures for each of the weapons on the planes they service. It’s not really a good idea to take a foreign-made missile and try to improvise a loading procedure with it. A well-disciplined crew wouldn’t even touch a missile if it was of an unfamiliar design and they hadn’t been thoroughly trained in how to load it, assuming its use on their planes was even physically possible.

Don’t forget about the red tape. It’s really tough to get approval to transfer any munitions tech from the US to non-Americans, and I imagine that the same is true of other countries.

“Hey, Chief, I just won an IRIS-T in a poker game with a bunch of Luftwaffe guys. Can I try sticking it on one of the Super Hornets?”

“Sure, why not? We don’t have a manual, but it’s mostly like a Sidewinder. We’ll just wing it. Get it, ‘wing it’. Ha, we have fun.”

Ha yeah, but what I was thinking of was the air forces that operate different types of fighters, like Malaysia’s MiG-29s and F-18 Hornets. It didn’t seem too extreme that, in wartime, if they lost all their MiGs (or Hornets) but still had some leftover missiles, that they would have planned many years in advance, “Hey, can we fit that AMRAAM onto this MiG (or Adder on to the F-18?)”

Assuming NATO specification conformance, if the decision is made to integrate the weapon with the aircraft, it will happen. The country of manufacture isn’t particularly relevant, other than as part of the integration decision.

Case in point: US ground-attack aircraft in Gulf War I used French-made Matra Durandal runway-cratering (rocket-assisted) bombs.

If no US munitions manufacturer has something to meet a specific mission need, the DoD will happily buy from an ally.

Yes, but in the Malaysian MiG and F-18 instance, the Malays couldn’t mate their Russian weapons to Hornets and vice versa, right?

In a certain sense, anything can be cobbled to anything else, given enough time, and given enough reason to do it. Bear in mind the reason to do it might likely be itself time sensitive.

Pylons can be fabricated; software can be patched; alterations in aerodynamics can be worked around. I recall even .303 rifles can be converted to .22 by the insertion of tubes down the barrel and modifying the loading apparatus.

But time is the critical player.

Specialisation tends to exclude adaptability and flexibility very quickly as one climbs the scale of tech advance. If all you have is a catapult, pretty much any old rock of appropriate size lying around will do. Arquebusses could be loaded with scrap metal. But by the time you get to aircraft weapons, a systems approach is necessary, so that the weapons are designed (or adapted) parallel with the airframe. They are perfected together long before their need in battle arises.

And for obvious political reasons, countries like the US, China and Russia build their own systems from scratch. While it might be possible in some sense to cobble a Russian rocket onto an F18, the real question is one of timing and planning. How long will it take you to whip up a poorly tested kluge as against begging down the line to Uncle Sam for a plane load of proper weapons? If you have not bought enough of some type of ordnance in advance, and in the middle of a battle run out, that is bad planning, but the demand for replacement weapons is likely to be so time critical that noodling about with a screwdriver and some software is never going to be a practical solution. As the old saying goes, amateur generals talk tactics, professional ones talk logistics. If you are in such a hole that you are even thinking about the need to cobble together Russian and US weapons, you lost the logistics war long before.

First it needs to hang on the rack. If your plane has a standard NATO rack, and the weapon is NATO, then the launch rails will mount up. Other weapons, probably not.

But that’s only the first part. You need to hook it up. The electrical connectors are different, so you’ll have to make some that match. What signals are required? What are the power requirements? Do you even have a spare breaker? Don’t forget to wire up the “weapon present” loop so the aircraft knows it is there.

What software is needed? If the aircraft/helicopter software doesn’t support the weapon, it won’t show up as a choice in the display. It’ll just be dead weight.

Now comes the engineering part. What happens to the aircraft when you fire this strange new missile? Do the exhaust gasses burn the wing? Get sucked into the engine and cause a flameout? Will it ignite the fuel vent vapors? The missiles on the next rack? What does firing it do to the cg? Can the aircraft survive the loads from a hang fire?

How is the accuracy? If you’ve gotten this far, you’ll still need to do a lot of test firing to verify the weapon can even hit what you want.

And what happens in an emergency? If you have to pickle the weapons, will they clear the fuselage in all flight attitudes? You’ll never get a pilot to fly if he’s in a much danger of dying from the weapon as is the enemy!

Think out of the box!

I’d imagine that they might be motivated to do so as the alien city-buster ship* was bearing down upon their base, and those missiles were the only option available.

*And why are they sooo slow?

But note that bombs (which are dropped from the plane and fall a long way before going off) are quite different from missiles, which are fired off right there under your wings.

I’m thinking it’s partly a matter of trust. Something like a missile, the only thing stopping the warhead from detonating whenever is the computer inside the missile, right? Would you trust munitions made by a foreign power? Well…

And partly production volumes. Any real war, you’re gonna need a crap-ton of the munition in question.

But yeah it seems like you ought to be able to just CNC up an adapter relatively quickly that screws into whatever socket is on the aircraft for the pylon itself and has the right mounting solution for the missile. Inside the adapter would be a circuit card. If you were in a huge rush, you’d have a marginally mil-spec custom circuit board in there. One one side it would receive commands from the aircraft’s communication bus “start missile, get status, launch missile” and the other side it would send commands on whatever bus format and baudrate and voltages the missile is expecting to receive.

There’s RS-485 and CAN bus and serial and all kinds of one-off military busses I don’t know about. Each one electrically would use different timings, different voltages, and so on.

In addition, something like a missile will probably require that you “sign” a command. Maybe just with a checksum or CRC, maybe with a frame sequence number and CRC, maybe a public/private key.

Come to think of it, this is harder than it sounds. If you don’t have access to the original documentation this would not even be possible.

Integrating a new weapon into an aircraft system is a rather long and costly process. To illustrate why, we can go through the life of e.g. an air to air missile on a fighter Jet from loading to firing to see what happens

At first, it gets loaded onto the aircraft, usually onto a pylon under the wing or weapons station on the fuselage. This interface needs to be compatible, otherwise you run into the first problem. Additionally, the missile gets connected to the aircraft systems. Here you might also have an incompatibility if the plug on the aircraft does not fit the missile. Even if physically compatible, the aircraft system might use a different bus system (e.g. different Signal types, Levels etc).

Let’s assume that we got the missile fitted and connected. The next problem is flight physics and mechanics. If you strap something to a wing, you create drag and additional forces, e.g. when doing a high g turn, so you need to make sure that your aircraft can take these Forces without breaking apart. Furthermore, depending on the missile mass, Center of gravity and Moment of inertia, you could induce something called flutter in the wing (see e.g. this video https://www.youtube.com/watch?v=egDWh7jnNic) which can destroy your aircraft pretty fast.

Next up is the targeting information. You made it into the air without the missile falling off or your aircraft shaking apart and you find another aircraft you want to fire upon. Most modern missiles (e.g. AMRAAM, AIM-9X etc.) get a lot of information from the aircraft systems regarding which target you want to fire upon, where the target is relative to you etc. The seeker head for the AIM-9X for example can be controlled by the pilot by turning her head towards the intended target. This communication interface needs to be programmed.

You finally were able to get a target lock and push the weapons release button. Depending on where the missile is attached to the aircraft it is not just fired. To get enough separation between the aircraft and the missile, they usually get ejected and then fired. Depending on the combination, the ejection force (or lack thereof) something like this https://www.youtube.com/watch?v=fPTnmZ_HPAs might happen. Even if you just fire it of the rails like this https://www.youtube.com/watch?v=i_vwxDDFnv4 you still might run into problems if it does not leave the rail as planned, because now you have a rocket engine strapped to your wing or if the exhaust singes your aircraft.

So all in all, there are a lot of things that need consideration when integrating a modern weapon on a modern aircraft. The only thing that might be realistically feasible with less effort is to integrate a dumb bomb onto a slow flying aircraft with compatible harware interfaces.

Missiles? We don’t even use conventional ammunition unless it’s NATO standard. We (the US) require complete production records to include all destructive and non-destructive testing related to production. The ammunition is grouped into lots by manufacturing and supply chain down to the smallest component and material. This includes screws, coatings, alloys. Missiles are further broken down by individual serial number. Case in point. During Desert Storm II, electric boogaloo, the powers asked if we (ammo guys) could authorize US troops to fire 155mm HE projectiles and propellant that Saddam had laying around in great quantities. NO. Research showed we (US) had licensed production of the M107 round to 17 other countries but no one did it quite the same way. Dimensionally every thing was good but: We X-rayed the body after the steel billet was forged. X-rayed again after welding on the base closure, X-rayed again after the TNT / Comp B was poured into the shell. We maintained complete records from production of the original steel alloy. We also had/have a robust suspension/restriction program that monitored the projectile lots until expenditure or demilitarization. We had no records to trace any foreign production. Use was “absolutely not.”

The propellant was a no-go from the start. Most artillery is nitro-cellulose based and begins deteriorating the day after it was produced. We monitor master samples direct from production and fielded quantities on a periodic basis. When the stabilizer is consumed, any remaining propellant from that lot of production is destroyed. Laying around in the desert heat/cold cycles with no records; we burned 70,000 to 100,000 lbs. each slow (rainy) day to get rid of the foreign propellant before self-ignition got started at just the one site I was at (Objective Arlington). This was for a dumb HE projectile and bulk propellant; a missile is out of the question.

There was one exception: 7.62mm and 5.56mm rounds are standardized within NATO. The .50 cal rounds are not. In actuality, NATO allies all make the .50 cal rounds alike, the links are the same, they even come in the same M2A1 can in 100 round increments. European production differs in the propellant (environmental constraints) and is slightly “dirtier” in the chamber and barrel (you have to clean the weapon after each engagement which should be done anyway). US forces were short .50 cal rounds - long story - but Saddam had a couple hundred thousand new in cans from the French some years back. We did some test firing at the base and the rounds performed well. Word got out and our local protectors - M1 tankers - requested all we had beyond our own use. I explained the potential fouling problem, they tested, and enthusiastically used up the rest until US supplies caught up. Wasn’t strictly legitimate but we did test fire, emphasized the cleaning aspect AND we were out of .50 cal. This was a shooting scenario, not some training exercise.

I will comment that these are the actions by a wealth country. Not just a wealthy country, but the payer (the DoD) isn’t spending it’s own money per say. And all this careful work happens to enrich defense contractors who happen to fund lobbyists who happen to give money to politicians who write up the budget and decide how much to borrow from China to fund it all.

With that said, another big difference between 50 cal rounds and artillery rounds is that if the warhead in the artillery shell goes off inside the barrel, it’s going to kill the crewand soldiers nearby. If the propellant in the 50 cal round is a little hot it’s not going to break the barrel, and machine gun barrel breaches will generally at most injure the gunner.

What kinds of armament do Iran’s F-14 Tomcats use ? Just the missiles and projectiles that came with the planes in the 1970s ?

Those, and refurbished ones, and reportedly reverse-engineered copies…plus American surface to air missiles modified to be air-launched.

Technically not the craziest after-market aircraft weapon I’ve heard of, at that.