Since some are wandering about the issue, this post is an explanation of why we can't just integrate AMRAAM on our JF-17.
Lets explain just one of the several issues.
One of the most fundamental reasons, we cannot integrate AMRAAM missile with JF-17 aircraft is lack of access to the accurate missile dynamics model for the AMRAAM.
In general, a missile dynamics model includes details of missile motion parameters such as its turning performance, climb rate, velocity ranges etc. as well as its response to aerodynamic forces and moments ( i.e. torques) due to changes in its control surfaces, thrust vectoring as well as due to the deformations of missile body and control surfaces. In other words such a model tell us how the motion of the missile is affected by control inputs that reorient the missile control surfaces as well as thrust vectoring nozzles (in case missile has thrust vectoring incorporated) to achieve a certain performance.
Even when the two missile looks exactly the same with exactly the same control surfaces and thrust vectoring, their motion may be completely different. This may be due to a variety of factors. For example the missiles in question may have bodies made of different materials leading to different deformation patterns under the same load which would make them experience different aerodynamic forces as result, leading to different motion. This is because motion is a function of aerodynamic forces and moments experienced by the missile. As the missile surface deforms anywhere, the nature of aerodynamic forces acting on it changes which leads to different dynamic behavior of the missile. Furthermore how the mass is distributed within the missile (i.e. its inertial properties), burning solid fuel geometry etc. also have profound impact on how the missile is going to behave when subject to certain aerodynamic forces.
In plain English what I’m trying to say is, as we all already know, each missile is different than the other even when they look and appear to be the same.
This difference is captured in what is known as missile dynamical model which uniquely characterizes each missile performance .
In other words a mathematical model of the missile tells us how the missile is going to behave under what kind of conditions. More specifically the mathematical model of the missile tells us about its performance i.e. things such as how best it can turn when traveling at a certain velocity without breaking up or deforming too much leading to increased drag and resulting energy losses or without experiencing flutter etc. This mathematical model can predict things such as how high it can fly, how fast it can travel in short what’s the best it can do under what circumstances.
If you have such a mathematical model for a missile then we can incorporate such a missile model within our aircraft’s weapons computer. Without it aircraft cannot effectively integrate a new missile.
So why would aircraft’s weapons software module need a high fidelity meaning extremely accurate mathematical model of the missile?
Well the answer is simple and most readers probably already know that. We want to launch a missile when you have high enough probability of kill. When the aircraft is flying, around it there is always a volume of space within which a "missile with a certain performance" can destroy a "certain kind of aircraft" with a high probability of kill.
This volume depends on both the missile and the performance of the target aircraft. In most real world cases we do not know the target motion characteristics in advance, in other words performance of the enemy aircraft is unknown. Still we can assume it in a probabilistic sense and even update it based on intelligence, industrial espionage, or just observation of the aircraft motion during actual engagement. Which leaves us the need to have missile motion model so that we can calculate its probability of kill within a certain range around our aircraft. This way if the probability of kill is high, we will launch the missile and won’t end up wasting it.
In every aircraft say F-35, F-16 etc., weapons aiming computer/software continuously calculates the probability of kill for each target. It can only do it if it has a high fidelity missile model. Since without it, weapons aiming computer cannot calculate accurately whether a certain missile can perform a certain motion necessary (i.e. can take certain amount of turns, can accelerate to a certain velocity in a given time etc.) to hunt down the enemy aircraft. For a given target this probability of kill is then used to calculate “the launch success zone”, within which if a given missile is launched, it has a high enough probability of kill.
In conclusion, therefore to achieve a high probability of kill we need a highly accurate missile dynamics model. This mathematical model, usually a 6 degree of freedom model in its best form, represents the true performance of the missile under all operational circumstances. In other words a high fidelity model is used to calculate the probability of kill which guides the pilot (i.e. gives him/her cues when to shoot) so as to when to fire the missile under the right circumstances. Without it pilot will be very ill-informed on what to do. Do realize that the aiming software does that for the pilot, calculating moment by moment what needs to be done. Such calculations are extremely fundamental to successful kill since successful attack depends on sometimes split-second accuracy. That is if we missed the fire-window for a second, our missile may not have the performance necessary to successfully hunt down the enemy aircraft.
So in conclusion to integrate a certain missile with every aircraft requires supplying the aircraft manufacturer with the high fidelity missile mathematical model. This is usually given by the missile maker after a lot of legal paperwork to safe guard the technology.
If we are not given such a high fidelity missile model by the missile supplier, then in principle we can still estimate such a mathematical model using techniques such as system identification (using either frequency domain or time domain approaches).
But that would mean buying the missiles, attaching additional sensors on them for data collection, firing them on extremely highly maneuvering targets so as to push the missiles to their limits and then based on measurements of their motion parameters (i.e. velocity, angular velocity such as turn rates etc.) among other things, calculating the required high fidelity missile dynamics model. Which means wasting dozens of missiles for such a task.
Once we have such data, we can calculate the required high fidelity missile model for any missile. Any masters in aerospace engineering who has taken a system identification course can do that (though post PhD is a better candidate for such a job since he/she likely has greater mastery, but it depends). While companies do keep their missile dynamical models a.k.a. missile dynamics models secret, they do supply them to aircraft manufacturers within their own country. Also they do know and fully understand that any country with a reasonable technical ability can estimate such high fidelity mathematical models of the purchased missiles.
As I said an average PhD who has worked on system identification for a while or even a masters student can do it as part of his/her masters level research, though it might actually lead to thesis good enough for a PhD. Note that does not include data collection effort. We are assuming data is being collected by Pakistan airforce engineers. Then such a PhD thesis can be produced, providing us with the missile dynamics modal. Collecting data itself is a separate headache.
There are other ways to calculate missile dynamics models which are usually too complicated and too involved. For example, in principle we might be able to do it by first extensively characterizing the various properties of the missile such as its inertial properties (due to mass distribution), structural properties, thrust and aerodynamic response characteristics (from CFD or wind tunnel testing). But that would be quite complex and frankly requires too many resources. It may save the missiles since we don’t have to fire them (and waste them as result) in this case but otherwise it would be costly in its right, time consuming and most importantly personal consuming task. We can also estimate such a missile model, from missile hardware and software analysis using an approach called "formal methods" but that would be extremely time consuming and complex also. Or we can a mix of the above approaches.
There are other issues which are too specific for given missiles, sensor systems and aircraft firing those missiles. These are too technical and require too much typing to explain them.
Rest assured Pakistan can in principle integrate AMRAAM with JF-17 but that would mean wasting a lot of missiles to collect data or spending a lot of resources to develop accurate missile dynamics model as described above. It’s much better and safer to just buy the Chinese PL-15 for JF-17.
Of course it is possible that after we have calculated a high fidelity missile dynamics model, Americans may force us not to integrate their missile on our aircraft anyway. Which would mean waste of effort. But from a technical and engineering point of view the main fundamental problems can be solved by us, absolutely. We can integrate any missile if we are determined enough and most importantly can face the political pressure if any.
On the other hand, if we have enemy missile dynamics models, we can then in principle (read in principle) incorporate that into our aircraft flight control software so that it can guide the pilot so that he/she can best avoid the missile. That's why countries do not supply such models.
IF we get our hands on say few indian missile or collect enough data on those missile flying around, we can synthesis a mathematical model of those missiles quite accurately which we can then use to update our flight simulators and train our pilots to best avoid them.
P.S. Kindly, this would be my last post for a while.