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A common theory from pro-Russian netizens surrounding the MH-17 tragedy is that it was a Ukrainian SU-25 ground attack fighter plane which shot down the civilian airliner. However, MH-17 was flying at 10,500m when the service ceiling of an SU-25 is 7,000m. They say that this discrepancy is made by the fact that the Ukrainian pilot used afterburners to get to the height MH-17 was flying at. Is this actually technically possible?

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The SU-25 looks wimpy, isn't it possible they used a better fighter jet such as a MiG? –  shortstheory Aug 27 at 7:57
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@shortstheory I guess the rumour specifically mentions the Su-25 because they were being used in the area around the time: one of them was shot down a few days before the MH-17 shoot-down, for example. –  David Richerby Aug 27 at 8:17
    
@DavidRicherby the Russians have also specifically claimed that they tracked an Su-25 close to MH-17 around the time of the attack –  Nigel Harper Aug 27 at 8:24
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@shortstheory they never do, you also have to consider what its mission is. And its mission doesn't require high speed or a high service ceiling (though the latter can be handy for ferry flights of course, but then again do you give a bulldozer roadwheels so it can drive on the motorway? of course not.) –  jwenting Aug 28 at 5:01
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It would be hard for a pilot to use afterburners on an Su-25, since it is powered by non-afterburning turbojets! :) –  egid Aug 28 at 6:12

3 Answers 3

up vote 36 down vote accepted

There is an excellent answer at http://scottlocklin.wordpress.com/2014/07/21/can-the-su-25-intercept-and-shoot-down-a-777/

  • The SU-25 is a ground attack fighter unsuited to intercepting and/or shooting down 777s. If the Ukrainian air force wanted to do so, they have better aircraft available.
  • The SU-25 max speed is slower than a cruising 777.
  • The SU-25 has an operational ceiling of 16000 ft with max weapons to 23000 ft clean, MH17 was at 33000 ft.
  • It is an unpressurised aircraft.
  • As a ground attack aircraft it probably only rarely carries air to air missiles. It can carry the R-60 infra-red air-to-air missile which has a 6 lb warhead effective against small aircraft.
    • An R-60 once hit and destroyed one engine of a small BAE 125 business jet at 35000 ft but failed to bring it down, apparently the missile failed to explode.
    • KAL902, a Boeing 707, was hit by an R-60 and made an emergency landing 40 minutes later.
  • The R-60 is a short-range missile (5 miles). The Russians claim the SU-25 came within two or three miles of MH17.

On the whole this makes the SU-25 a poor choice for shooting down a cruising 777.

It seems unlikely that a 777 would be shot down in this way. Not impossible, but far less likely than other proposed scenarios such as those involving BUK (SA-11) ground to air missiles.

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Results of an R-60 hitting a jet engine on a small business jet.

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Results of an R-60 hitting a Boeing 707 ... two R-60s were launched, one missed.

These R-60s were fired by supersonic interceptors, not by SU-25 ground-attack aircraft.

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Any idea why these pro-Russian netizens accuse the SU-25 instead of accusing a more suitable fighter available to Ukraine? I wonder if what's happening here is that some very sloppy conspiracy theorists are getting in the way of more competent attempts to blame it on Ukraine by creating a ready-made straw man argument ;-) –  Steve Jessop Aug 26 at 18:15
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@SteveJessop: I suspect the accusation was primarily intended for domestic audience as Putin gained huge popularity with the aggressive approach to Ukraine and couldn't admit mistake. And for commoners accusing Su-25 that is known to operate in the area might be more believable than accusing more suitable fighter that nobody mentioned so far though it makes the accusation clearly false to the knowledgeable. The accusation came from Ministry of Defence, so sloppy conspiracy theorist don't sound likely. –  Jan Hudec Aug 26 at 21:24
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@SteveJessop ever met a conspiracy theorist who knew what he was talking about? If you can come up with an improbable aircraft for the scenario, you can dream up improbable things like rocket engines strapped under the wings to get it up there as well (not that farfetched, such things were attempted with interceptors in the 1950s, but not realistic in this case, especially as the missile tracks coming out of Russian held territory intercepting the airliner were recorded). –  jwenting Aug 27 at 6:37
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@jwenting: The missile track is what I am most willing to discredit, because that is a word of USA Ministry of Defense (claiming to have recorded the track) against work of Russian Ministry of Defense (pushing this Su-25 theory). I consider the comments made by the separatists on Twitter and then deleted as more important evidence because the dynamics of the situation would make that much more difficult to fake. –  Jan Hudec Aug 27 at 7:20
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@JanHudec me too, I have my doubts about anyone's ability to record a missile track on radar like that unless they're deliberately looking for it at the time. And the US had no reason to have assets looking for missile tracks over the Ukraine that day. –  jwenting Aug 27 at 7:27

You're asking 4 things here:

  1. Can aircraft fly higher than their stated service ceiling?

    Service ceiling can be exceeded, depending on the aircraft type, loadout, atmospheric conditions, and flight profile, but usually not very far or for very long.

  2. Does an SU-25 have afterburners?

    The SU-25 (NATO reporting name Frogfoot) has no afterburners, so that part of the claim is bonkers.

  3. Does an SU-25 have the capability to shoot down aircraft?

    It can carry light IR guided missiles for self defense, and of course has a gun, but would have no way to intercept an airliner at altitude, it doesn't have the endurance there nor the equipment to detect and track the aircraft (though in theory a ground controller could guide it of course).

  4. Would an SU-25 be used for an intercept like that?

    Why should the Ukraine use an SU-25 ground attack aircraft when they have dedicated air defense fighters far more capable for the job?

So no, the claim is utterly bonkers.

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The SU-25 has a very powerful gun, though--it's meant to tear through tanks, it certainly could shred an airplane. Finding it, getting up there and getting hits would be very problematic indeed, though. –  Loren Pechtel Aug 26 at 22:47
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@LorenPechtel yes, it does (as I mentioned). And weirder things have brought down aircraft. For example in Iraq a USAF A-10 brought down a helicopter by dropping a 500lb bomb on it :) –  jwenting Aug 27 at 6:34
    
@LorenPechtel: Yes it does. But for one thing if it can't reach the altitude, the distance would be rather large for good aim and for another the damage would look different from the shrapnel damage that was actually observed. –  Jan Hudec Aug 27 at 7:00
    
… which leads me to another argument. The debris show shrapnel damage to the front section of the aircraft. That is not consistent with IR-guided missile which would go for the engines from behind nor with cannon with shells exploding on contact. It also indicates heavier warhead than the few kg found in most air-to-air missiles. –  Jan Hudec Aug 27 at 7:05
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@JanHudec Most A2A missiles use proximity fuses and there are an enormous number of variables determining the area of the aircraft taking the brunt of the damage. Because the nose is peppered means nothing. Nor does the amount of damage correlate to the assumed weight of the warhead. The conspiracy theory is, as they always are, nonsense but the size and area of damage are not indicators (without other evidence) to prove or disprove air-2-air or ground-2-air. –  Simon Aug 27 at 19:58

Parabolic trajectories above the service ceiling are possible. Just go up fast enough, and rely on inertia instead of lift to carry you upwards.

Of course, parabola's have the property that there's a long way up, a sharpish bend at the top, and a long way down again. That's not a practical way to intercept another aircraft, especially if your plane isn't designed to use off-board AA radar guidance to get the intercept course right (and a ground attack aircraft like the SU-25 wasn't designed like that at all - The Soviets had proper high-altitude interceptors for that)

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More importantly you are exchanging speed for altitude, so at the top you are flying slower. And you must still fly fast enough to be above stall speed and (true) stall speed increases with altitude. So the aircraft would have to fly very fast before starting the climb. With the altitude difference probably faster than it's actual top speed. –  Jan Hudec Aug 26 at 20:49
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To put some numbers out: Looking over how the zero-g flights are conducted we find that you can trade 260kph for 1000m of height. With more engine power you could get higher but you still have to fly a course between the Scylla of mach buffet and the Charybdis of stall and unless I'm making a math error you're not going to get 2000m out of it. –  Loren Pechtel Aug 26 at 23:02
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Flying on such parabolic trajectories also reduces the aircraft's ground speed as most of the speed is in the vertical direction. Which means it makes the already slow aircraft very much slower than the 777's cruising speed. So the only viable way for it to work is if the pilot starts climbing very far ahead of the 777 hoping to reach max altitude exactly when the 777 arrive. That's just silly. –  slebetman Aug 27 at 14:54

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