First, a disclaimer: I am not a pilot nor an air traffic controller, and I never served with air defense units. I did spend some time with an airforce, but my role was one of electronic intercept analysis. So what follows are just the musings of an uninformed amateur. Caveat emptor.
What I will try to do here is present a possible scenario which takes into account the basic facts established so far. Here goes:
The plan was for the Ukies to shoot down the MH17 using a totally inappropriate aircraft: the Su-25, which is a “tree hugging” close air support aircraft. Why? After all, the Ukies do have some Mig-29s and even some Su-27, but these are much fewer in number and much easier to track. A few of them have been seen in the skies over Novorussia, but only rarely. In contrast, the Su-25 has been a ever-present presence in the skies ever since the conflict began. Some say that the Su-25 cannot fly over 7’000m. That is not true. The problem is that it’s cockpit is not pressurized, but the airframe itself has powerful engines which can bring the aircraft well over 10’000m. All the pilot would need is some good warm clothing and an oxygen mask. No, the big drawback of sending the Su-25 so high is that it’s engines are not designed to be used at that altitude and that it will not be able to fly fast enough to catch-up with a cruising Boeing. But what if the Su-25 carried a missile?
Turns out that the Su-25 can carry the R-60 air-to-air missile which can fly at over 3’000km per hour and thus easily catch up with a cruising airliner. So the Su-25+R-60 combination has a flight envelope which is sufficient to attack a Boeing.
There is something else that the Su-25 lacks to function has an interceptor: a radar. Well, this is not quite true, the Su-25 has a radar, but it is designed for navigation, not air-to-air combat. However, the R-60 missile does not need a radar, it has its own infrared homing warhead. So if the pilot of the Su-25 can point his aircraft in the general direction of a heat emitting target, and if that target is not too fast or too far away, the R-60 will be able to lock on to it and close in. The R-60 is a pretty small missile with a short range, under 8’000m, but it so happens that that Russian radar operators reported the Su-25 at about 3-5’000m from MH17.
Still, it is not easy to visually acquire the correct aircraft from the cockpit of a Su-25, then get within the correct range and then fire. There are clouds, sunlight, other aircraft. And the Su-25 has no air-to-air radar with a search and track mode. So what could the Ukies have done? Provided another radar?
In comes the 3 BukM1 transporter erector launcher and radar (TELAR) and the at least one early warning (long range) radar which all had just been moved in the day before MH17 was shot down, and then immediately withdrawn. The radars of each Buk TELAR and the long range early warning radar whose signal have been detected by the Russians could have easily guided the Su-25 to its target, either by a encrypted datalink or even by radio commands.
Combining all of the above, here is my totally primitive and possibly completely mistaken hypothesis:
The Ukies guided the Su-25 to MH17 by using the Buk radar capabilities. As soon as he was in reach, the SU-25 fire a R-60 missile which hit one of the two engines. At this point, the MH17 sharply turned to one side and lost altitude (the hit engine would lose power and its drag would sharply pull the Boeing to one side). The Su-25 then easily closed in and opened fire with his cannon, which has a range of 4’000m, shredding the cockpit and cabin with 30mm rounds. Had the pilot of the Su-25 failed to catch with MH17 or if the R-60 missile had failed, the Buks on the ground were ready to shoot, but they probably did not have to. Once MH17 was clearly destroyed, the pilot of the Su-25 could have easily landed anywhere in the Ukraine without drawing any attention.
This was a good plan, but it failed to take into account the sharp turn made by MH17 which instead of continuing on its path towards Russia turned around and fell into a contested by Resistance-controlled field.
One more thing: if my hypothesis is correct and the first impact on MH17 was from a rather small R-60 missile (3kg warhead) into an engine, the flight deck did probably not suffer an immediate and catastrophic depressurization. If so, the pilots would have had the time to report an explosion. This is why the recordings of the Kiev ATC were seized by the SBU and why the result of the analysis of the flight recorders takes so much time: the Empire needs to wipe away the recording of the pilots’ last words. Conversely, if MH17 had been destroyed by a BukM1 missile (70kg warhead) the depressurization would have been immediate and catastrophic. The problem with wiping the flight recorders is that if the pilots had the time to send a mayday then it would have been recorded not only by the USA and Russia, but by at least two more West European countries. Even if the latter would comply with the US orders, the Americans are probably terrified that the Russians have the recordings of the MH17’s mayday and they are probably trying to negotiate a deal with Russia. If not, they need to carefully prepare the public opinion by, for example, organizing careful leaks through the Dutch and Malaysian press to say that nothing was recorded in order to denounce any recording presented by Russia as a “fake”. All of this is, again, pure speculation on my part.
Ok, now please feel free to tear this hypothesis into shreds. These are just the musings of an amateur and most definitely not an expert opinion. I submit it only as a basis for discussion.