Why Does this Syrian Mil-8 Hip (Russian helo) Explode in Midair?

[Broncazonk]

Okay, here we go again. The question is: Why does this helo suffer from a midair catastrophic explosion? Turbine/turboshaft powered helos burn Jet A or Jet A-1 or JP-8 fuel which is kerosene based and while said fuel will burn uncontrollably, it usually will not go BOOM.

Please: No more cultural commentary as nobody cares how immature and culturally ignorant you are. Thank you.

http://www.youtube.com/watch?v=v3bdOoZn8x4

Bronc

 

[circle-5]

Please: No more cultural commentary as nobody cares how immature and culturally ignorant you are.

I always felt I might be immature and ignorant. I just needed someone to tell me. In bold letters, thankfully, because us kind of people is also blind.

 

[Orionblamblam]

The question is: Why does this helo suffer from a midair catastrophic explosion?

It's a military helicopter in a combat zone, it's out of control and on fire. Chances are good that something onboard kerploded. It's a chopper that often carries combat troops, so it's not unreasonable that someone onboard - in the process of being tossed around the cabin - touched off an RPG.

It's real honest-to-Admial-Ackbar onboard detonation from the looks of it, not something sedate like the fuel tank busting open. No AAM trail seems visible, so whatever happened, happened onboard.

Please: No more cultural commentary as nobody cares how immature and culturally ignorant you are. Thank you.

Say... isn't insulting someone because you disagree with them "cultural commentary?" It's a trap!

 

[chuck4]

It's one hell of an RPG to explode into a persistant fireball several times the size of a large helicopter.

 

[Abraham Gubler]

The nature of the explosion is a fuel feed fireball. Explosives don't blow up like this expect in Hollywood. As the chopper is falling you can see it leaving behind quite a 'smoke' trail which is probably fuel. I would expect said fuel and vapour was also filling the cabin of the chopper. It doesn't look as if there was anything burning in the aircraft after the initial hit but with enough fuel splling out and at least one engine still in operation or the aircrew trying to start them there are plenty of normal sorces of ignition. Despite it being jet fuel that doesn't mean it won't explode. Lots of jet fuel explosions in aircraft in this world to date.

 

[Broncazonk]

Thank you Abraham for your reply. The helo lacks self-sealing fuel tanks from the apparent amount of fuel in the air? This was like a fuel in air detonation then?

Bronc

 

[GTX]

Enough holes or a big enough hole in any fuel tank even a self sealing one will result in fuel loss. Just because they are self sealing doesn't make them impervious to all damage.

 

[Orionblamblam]

This was like a fuel in air detonation then?

Very unlikely. True detonations with fuel & air require either confinement (to produce a "pipe bomb" effect), or some fairly impressive supersonic shockwaves... the kind that might be found in regular military explosives going off.

No doubt fuel burning is what made the fireball, but somethig else very likey touched it off. Helicopters, unlike Hollywood cars, don't just explode because the fuel tank is leaking.

 

[Abraham Gubler]

No doubt fuel burning is what made the fireball, but somethig else very likey touched it off. Helicopters, unlike Hollywood cars, don't just explode because the fuel tank is leaking.

The fuel tanks aren’t just leaking they are completely perforated. That is an enormous amount of fuel flowing out the back of this aircraft. It is no doubt filling the interior of the aircraft and up into the engine bays as it is probably pulling some negative G in it’s downwards spin.

On the other hand there is no indication of some other explosion causing a fireball secondary. We could expect to see some indication of this before the fuel ignites but there is nothing. Nor is there a logical explanation as to what would have caused a primary explosion? The helo takes no further fires and if there was a smouldering fire on-board causing something to explode it would have ignited all that fuel pouring out the back.

For the record if you get a regular car, flip it onto its roof, perforate the fuel tank and leave the engine running (which usually doesn’t happen in natural occurrences of cars being flipped and fuel tanks pierced) then you will get a fireball.

 

[Pioneer]

My 20-cents worth............

It appears to be a standard transport variant of the Hip. Hence minimal protective armour!
I support the analogy of a simple fuel cook-off, as the stricken plummets to earth, which results in a catastrophic explosion.

It would be interesting to find out what weapon was used to initially take out the Hip, as it was at a decent altitude! My guess is a MANPAD

Regards
Pioneer

 

[Orionblamblam]

For the record if you get a regular car, flip it onto its roof, perforate the fuel tank and leave the engine running (which usually doesn’t happen in natural occurrences of cars being flipped and fuel tanks pierced) then you will get a fireball.

A fireball, yes, but not an explosion that blows the cars into flinders. Note that the helicopter isn't simply engulfed in a fireball... it's *gone.* A fuel deflagration isn't going to do that; a detonation, and a sizable one, is what's needed.

 

[Broncazonk]

A fireball, yes, but not an explosion that blows the cars into flinders. Note that the helicopter isn't simply engulfed in a fireball... it's gone. A fuel deflagration isn't going to do that; a detonation, and a sizable one, is what's needed.

Well, that's what I found so unusual. The explosion vaporized the helo. Maybe a piece or two came falling out, but for the most part it was gone.

On the other hand, from the color of the fire, and the lack of a high velocity shock wave, this looks like a great big "Hollywood" fuel explosion without any enhancing/secondary explosives.

Look at this video--another Syrian helo going down on fire.

http://www.youtube.com/watch?v=gtSJzODchj0&feature=fvsr

This is more "normal." One thing is for certain: Mil-8 Hip pilots and crew deserve credit for flying them. They appear to burn like Japanese Zeros when they get hit.

Pioneer wrote, "It would be interesting to find out what weapon was used to initially take out the Hip, as it was at a decent altitude!" I'm hearing ZU-23-2 in the background.

Bronc

 

[GTX]

Mil-8 Hip pilots and crew deserve credit for flying them. They appear to burn like Japanese Zeros when they get hit.

Actually, from the accounts I have read, especially in Africa, the Hip family are very rugged (for a helicopter) designs that can withstand a lot of punishment. The term flying truck seems very appropriate.

 

[Orionblamblam]

Maybe a piece or two came falling out, but for the most part it was gone.

Indeed. It's like it was made out of cardboard.

On the other hand, from the color of the fire, and the lack of a high velocity shock wave, this looks like a great big "Hollywood" fuel explosion without any enhancing/secondary explosives.

The onboard explosion needed to be big enough to convert the chopper into confetti... but once it was big enough, it could've been a *lot* bigger, and the result would probably look about th same. The detonation would spray the fuel out in a nice big burst no matter what, and the fireball would look pretty much the same no matter what.

I remain of the opinion that some onboard explosives (anti-tank rockets,a box of grenades, some "car-bomb-in-a-kit" packages headed for Lebanon, whatever) were set off internally. The damage was done by the detonation; the pretty fireworks by deflagration.

 

[Abraham Gubler]

I remain of the opinion that some onboard explosives (anti-tank rockets,a box of grenades, some "car-bomb-in-a-kit" packages headed for Lebanon, whatever) were set off internally. The damage was done by the detonation; the pretty fireworks by deflagration.

But there is no visual evidence of another high explosives explosion especially one that would generate its own high energy fragments. Nor is there any indication of what would have ignited such an explosion.

Jet fuel is highly explosive. I don't know why people are claiming otherwise!

Further when the fuel explodes it forms three main fireballs. An initial smaller central one (fuel in the cabin) and two large sideways balls (fuel in the exterior sponsons). This circular arrangement of fireballs is why the smoke ring forms.

 

[Orionblamblam]

But there is no visual evidence of another high explosives explosion...

You mean other than the helicopter exploding?

Nor is there any indication of what would have ignited such an explosion.

You man other than a helicopter on fire and out of control?

Jet fuel is highly explosive.

No, it's not.

I don't know why people are claiming otherwise!

Physics. Jet fuel is *flammable,* not *explosive.* While Hollywood might not understand the difference, the real world does.

 

[Abraham Gubler]

You mean other than the helicopter exploding?

If a bomb of some sort had exploded to cause the fuel to explode where is the indication of a primary explosion. And why is there three fireball explosions? Did they happen to store their RPGs inside the fuel sponsons?

You man other than a helicopter on fire and out of control?

The helicopter is out of control but there is no indication that is on fire before the fuel explosion.

Physics. Jet fuel is *flammable,* not *explosive.* While Hollywood might not understand the difference, the real world does.

Actually jet fuel is not flammable, it is combustible. And since we are not dealing with kerosene in a controlled lab we have to take into account that its explosive limits are from 0.6 to 4.7% by volume in air. Explosions are just energetic ignitions and jet fuel has proven this quality time and time again.

 

[Broncazonk]

How about this possibility?

1) The helo's fuel tanks were full,
2) The fuel tanks got sieved by 14.5mm and 23mm ground fire,
3) Fuel began spewing out the holes and several hundred gallons exited the helo,
4) The fuel got mixed and distributed around the helo by the churning action of the blades,
5) A large 120 foot wide "bubble" formed around the helo, this bubble was super-saturated with jet fuel,
6) An ignition source,
7) KA-BOOM!
8) The KA-BOOM detonates the fuel in the fuel tanks and the helo disintegrates.

I don't know anything about this stuff, but does this seem plausible?

Bronc

 

[Orionblamblam]

You mean other than the helicopter exploding?

If a bomb of some sort had exploded to cause the fuel to explode where is the indication of a primary explosion.

The explosion is a pretty good indicator of an explosion. You know, the point at which the focus of the video changes from "helicoper in trouble" to "shower of fine particles."

And why is there three fireball explosions?

Because a helicopter is not a spherical chicken in a vacuum.

The helicopter is out of control but there is no indication that is on fire before the fuel explosion.

Other than the rather obvious smoke trail?

Physics. Jet fuel is *flammable,* not *explosive.* While Hollywood might not understand the difference, the real world does.

Actually jet fuel is not flammable, it is combustible.

Wanna think that one over?

	flammable (ˈflæməb ə l)
	— adj
	liable to catch fire; readily combustible; inflammable

Explosions are just energetic ignitions

Ahhh... no. Take a gallon of gasoline and pour it on a bonfire, you don't get an explosion. Pour it on a lit oxy-acetylene torch, about as energetic an igniter as you can get, you still don't get an explosion.

And perhaps you should think through the likely outcome of a gas-vapor explosion within the confines of a helicopter. Sure, it'll blow the doors off. But will it turn the helicopter into a cloud of *nothing?*

 

[Orionblamblam]

Here are the relevant frames from the video. One of the important things to note is the smoke trail. It's clearly a smoke trail rather than a fuel-mist trail because even though there is a *massive* fireball connected to it *and* below it, the trail makes absolutely no effort to catch fire. If we are to believe that "combustible-but-not-flammable" fuel made a detonation within the confines of the aircraft, it's a puzzlement why a big cloud of the stuff in the perfect position to catch fire didn't.

 

[Orionblamblam]

I don't know anything about this stuff, but does this seem plausible?

The stumbling block is that the helicopter got freakin' vaporized. Not what you see with leakin fuel tanks.

Additionally, while the video quality is sucko at best, you can see that the blast radiates from a central point, not a cloud of external flammableness.

 

[Abraham Gubler]

One of the important things to note is the smoke trail. It's clearly a smoke trail rather than a fuel-mist trail because even though there is a *massive* fireball connected to it *and* below it, the trail makes absolutely no effort to catch fire. If we are to believe that "combustible-but-not-flammable" fuel made a detonation within the confines of the aircraft, it's a puzzlement why a big cloud of the stuff in the perfect position to catch fire didn't.

Because fuel trails from flying aircraft don’t work like Wyile Coyote pouring a line of gunpowder from his Acme Road Runner trap. It is not a continuous line of fluid and has a range of disruptive effects upon it like wind and the blast shockwave.

I’ve seen multiple F-111 dump and burns and the fuel dump starts before the reheat provides the ignition and never has the trail of fuel been ignited only the new fuel being dumped into the flame. And that would be an ideal situation for a fuel cloud to form a flame trail.

If it was smoke from a fire we could expect to see some flames but there is no sign of that.

The stumbling block is that the helicopter got freakin' vaporized. Not what you see with leakin fuel tanks.

Jet fuel can provide very energetic explosions. But apply some context and a closer look at the evidence. The explosion does not vapourise the helicopter. You can see quite a few fragments coming out of the fireball. Including what clearly looks like rotors and the intact transmission from the rotor head to the counter torque rotor. The airframe has been vapourised but this is a cargo helicopter. It has no lift bearing wings, it has no pressurised fuselage. It is simply an aluminium can that has a massive fuel explosion go off inside it.

Additionally, while the video quality is sucko at best, you can see that the blast radiates from a central point, not a cloud of external flammableness

The entire point I’ve been making is the leaking fuel is filling the cabin creating a mixture of fuel and air ripe for a massive explosion. The cabin is at the centre of the Mi-8 helicopter. On these helicopters fuel is stored in sponsons yet there is clearly a fuel feed fireball from the centre of the aircraft with the two lateral sponsons causing their own fireballs. If this is not a fuel explosion in the centre cabin then why is there are centre cabin fireball? If there is some other type of explosive causing this central explosion there would be some sign of it. Which is another point I made from the beginning.

 

[yasotay]

Oh for Pete sake gents!

The darn thing blew up. Two or more aviators are beyond caring. Syria has one less helicopter.

Thats good news or bad news depending on where you live.

 

[Orionblamblam]

It is not a continuous line of fluid and has a range of disruptive effects upon it like wind and the blast shockwave.

The smoke trail leads *directly* into the fireball, before, during and after the exlosion. This would be the *perfect* setup for combustion, especially since the fuel is *above* the fireball, rather than below or to he side of it. And yet there is *zero* evidence of any flame propagation up the column of smoke. And that's because smoke, unlike jet fuel, desn't burn.

I’ve seen multiple F-111 dump and burns and the fuel dump starts before the reheat provides the ignition and never has the trail of fuel been ignited only the new fuel being dumped into the flame.

Tell me: how does the fire get going?

If it was smoke from a fire we could expect to see some flames but there is no sign of that.[/ quote]

1) The "sign of flames" *IS* the smoke.
2) It's clear that the fire is internal.




Lots of smoke. Little to no visible flame. Does this mean what we're seeing are actually clouds of jet fuel?

It is simply an aluminium can that has a massive fuel explosion go off inside it.

If by "fuel" you mean "high explosives with a hydrocarbon chaser," then, sure.

Some years back a 747 exploded due to a fuel-air mix in the gas tank. The plane was not destroyed utterly as this chopper was, ever though it had the bnefit o flying far, far fast. It was simply torn in two.That's because such fuel-air explosions have truckloads of heaving force, but crap for brisance.

The entire point I’ve been making is the leaking fuel is filling the cabin creating a mixture of fuel and air ripe for a massive explosion.

Yeah, but your point is not supported by the facts.

If this is not a fuel explosion in the centre cabin then why is there are centre cabin fireball?

Because the primary explosion scattered the fuel.

If there is some other type of explosive causing this central explosion there would be some sign of it.

What exactly would you expect to see that's not quite visible here?

 

[Abraham Gubler]

Oh for Pete sake gents!

The darn thing blew up. Two or more aviators are beyond caring. Syria has one less helicopter.

Thats good news or bad news depending on where you live.

AFAIK we are not having a personal battle but rather a debate of ideas and information. Which is good for knowledge and understanding. Since no one is calling each other names or whatever why not let us pursue the matter?

 

[Abraham Gubler]

The smoke trail leads *directly* into the fireball, before, during and after the exlosion. This would be the *perfect* setup for combustion, especially since the fuel is *above* the fireball, rather than below or to he side of it. And yet there is *zero* evidence of any flame propagation up the column of smoke. And that's because smoke, unlike jet fuel, desn't burn.

It would be a perfect setup for combustion if the vapour trail was a solid line of liquid as if poured out on the ground. But it isn’t, it’s a mist. And even if far more solid streams of dumped fuel don’t ignite in a manner never before seen in the world of aerospace accidents and shoot downs why should this one?

The Tell me: how does the fire get going?

It is ignited by hot compressed air.

1) The "sign of flames" *IS* the smoke.
2) It's clear that the fire is internal.

Some interesting photos but none support your argument on a detailed level. First of all those structures from winter built houses to hi rise buildings are far more solid and enclosed than a Mi-8 helicopter. Also none of those buildings are moving through air which fans flames. Show me a photo of an Mi-8 (or any other flying helicopter) that is on fire without any visible flames and you might have an argument.

The second big point your photos demonstrate is that smoke has certain colours. Light white smoke is only generated by grass fires. Anything more substantial has some solid medium grey smoke. Jet fuel and metals burning generates dark grey smoke. Unless they have a bale of hay in the back of the Mi-8 that is on fire this is not smoke coming from it.

1Some years back a 747 exploded due to a fuel-air mix in the gas tank. The plane was not destroyed utterly as this chopper was, ever though it had the bnefit o flying far, far fast. It was simply torn in two.That's because such fuel-air explosions have truckloads of heaving force, but crap for brisance.

Like I said before the fuselage of a 747 type aircraft is far strong than a cargo helicopter. Your explosion is from inside a fuel tank which is designed to be resilient.

 

[Bill Walker]

You guys need to read a recent copy of NFPA 921. The relationship between fuel type and smoke colour is generally discredited these days, because it is subject to so many "ifs" and "buts".

If the white trail is spilling fuel, that is a sign that fuel vapours could be accumulating inside and around the airframe. When they reach the right fuel/air ratio, and an ignition source is present, a very large fire ball could result. Remember, Hollywood fireballs are usually gasoline vapour, plus a relatively small ignition source. An RPG would do it, as Blamblam suggests, but so could a good size 24V arc.

If the white trail is smoke, then there is a competent ignition source on the aircraft, waiting for an adjacent fuel air mixture to reach the right ratio. I would have to call this one as "unknown cause", although Blamblam's scenario is plausible (but only one of several plausible ones). If you could get me some large chunks of wreckage, and video shot from different angles, I might be able to narrow it down a bit more .

The apparent three stage fire ball is very typical of fuel air explosions or rapid burns. As the aircraft spirals, different fuel/air ratios will accumulate inside various areas inside the helicopter from fluid leaks, and even outside the helicopter. The upwind side will have a different ratio than the downwind side, for example. All it takes is one zone to reach a combustable mixture ratio, and have an ignition source present, to go boom. The rapid release of heat resulting from the first event will upset the ratios in adjacent zones (by moving air and fuel around) and other zones may then light off within a fraction of a second.

Bill Walker, CFEI, CVFI

 

[Abraham Gubler]

You guys need to read a recent copy of NFPA 921. The relationship between fuel type and smoke colour is generally discredited these days, because it is subject to so many "ifs" and "buts".

Every image I’ve ever seen of a fuel jettison is a nice white mist of smoke coming out the back. Every image of a burning aircraft is thick black smoke.

An RPG would do it, as Blamblam suggests, but so could a good size 24V arc.

He is actually suggesting that the primary explosion from a non-fuel source is what caused the energetic explosion that blew the helicopter apart. No RPG could do that though of course it could be an ignition of a fuel based explosion.

You The apparent three stage fire ball is very typical of fuel air explosions or rapid burns. As the aircraft spirals, different fuel/air ratios will accumulate inside various areas inside the helicopter from fluid leaks, and even outside the helicopter.

What I’ve been saying from post #1 in this thread.

 

[Orionblamblam]

It would be a perfect setup for combustion if the vapour trail was a solid line of liquid as if poured out on the ground. But it isn’t, it’s a mist.

Oy.

If you want to guarantee ignition, "mist" is the way to go.

The Tell me: how does the fire get going?

It is ignited by hot compressed air.

But here you're arguing that not just "hot compressed air," but air that is actively *combusting* in direct contact with the supposed mist of fuel over a duration of several seconds, is unlikely to spark ignition?

Some interesting photos but none support your argument on a detailed level.

All show internal fires with external smoke but no external flame, adequately demonstrating that a helicopter on fire need not look like a Hollywood special effect.

Jet fuel and metals burning generates dark grey smoke.

Depends on the density of the smoke, doesn't it. A house on fire has nice dense smoke, because the smoke is in no hurry to go anywhere. With this burning helicopter, it's moving through the air at a pretty good clip. It's not burning terribly aggressively; it's a relatively small fire compared to a vehicle entirely engulfed in flames. But as to jet fuel fires being necessarily dark gray:

Huh?

Whuzzat?

Who's doin' what now?

And as for metal fires, the metal in question here would be, if any, aluminum. And you've never seen anything whiter than aluminum oxide smoke, lessin' it's magnesium oxide smoke. In any event, this is not an aluminum fire; the smoke comes most likely from a relatively small hydrocarbon fuel fire.

Like I said before the fuselage of a 747 type aircraft is far strong than a cargo helicopter.

A Russian cargo helicopter is not such weak structure that a relatively minor "puff" such as you'd get from a fuel-air burst would completely shred not only the cabin, but the tail, the rotors, the cockpit, the whole thing. What you'd get in such a case would most likely be to blow the thin skin off, leaving the structure kinda-sorta intact. Probably fold up the rotors. But not the utter devastation you see here.

 

[Orionblamblam]

Since no one is calling each other names or whatever why not let us pursue the matter?

 

[Orionblamblam]

Every image of a burning aircraft is thick black smoke.

ERRRRR. Wrong, but thanks for playing!

He is actually suggesting that the primary explosion from a non-fuel source is what caused the energetic explosion that blew the helicopter apart. No RPG could do that though of course

Ah. So it's impossible that something like an RPG could have set off a crate full of Semtex? Do we know what the chopper was carrying? It could have been troops. It could have been ammo. It could have been rockets, bombs, parts and technical crew for the forest moon. Unless a manifest has been made public, we don't know. But we *do* know that it was a military chopper in a combat zone. Such vehicles are known to carry loads of explosives. And loads of explosives are known to explode from time to time, especially when you shake them around and set them on fire, both events that were clearly happening inside this chopper. But has anyone *ever* seen a helicopter turn itself into chaff with nothing more than a fuel leak?

 

[Abraham Gubler]

Since no one is calling each other names or whatever why not let us pursue the matter?

OK I'll withdraw what I said about this being a polite conversation. It isn’t.

It’s the mighty ego of Scott Lowther and his grade school science providing scenario wish fulfilment. Far from making any informed scientific conclusions you have simple definition debating. When some acts like a lawyer in their argument it’s a *surefire* indication they don’t know what they are talking about.

On the other hand we have Bill Walker a certified vehicle fire inspector basically agreeing with my conclusion that the explosion is likely caused by fuel and fuel alone (with of course some sort of ignition). I think it’s safe to leave it there though I’m sure Scott will have to make a few more posts proving to anyone without any experience in fuel fires that he was right.

 

[Orionblamblam]

It’s the mighty ego of Scott Lowther and his grade school science providing scenario wish fulfilment.

Far from making any informed scientific conclusions you have simple definition debating. When some acts like a lawyer in their argument it’s a *surefire* indication they don’t know what they are talking about.

Ahem:

Physics. Jet fuel is *flammable,* not *explosive.* While Hollywood might not understand the difference, the real world does.

Actually jet fuel is not flammable, it is combustible.

I think we're done here.

 

[Jemiba]

After closing the first thread about this theme, I actually was positively surprised, as it seemed to
remain on a reasonable level of discussion. But I'm afraid, it's plummeting again.
So, for all participants, please remember:
All we have is a low-quality video ! It was really interesting to see, what amount of educated guesses
could be drawn from it, but we should realise, that without further information, it's just conjecture,
the really known facts were summed up by yasotay.
So, please calm down and stay to arguments without taunting or worse !

The thread still is open, I really hope, we can keep it that way !

 

[tahsin]

I haven't seen the first issue but in Turkey people were talking of barrel bombs carried by those helicopters and the reason was supposed to be one catching fire and exploding. The drift of the thread suggests that has been already ruled out, is that correct?

 

[Orionblamblam]

I haven't seen the first issue but in Turkey people were talking of barrel bombs carried by those helicopters and the reason was supposed to be one catching fire and exploding. The drift of the thread suggests that has been already ruled out, is that correct?

Oh, no. The evidence so far suggests:
1) The helicopter was out of control
2) There was an onboard fire
3) There was a *substantial* high explosive detonation

I was previously unaware of the "barrel bomb." But there are numerous references to them in the news:

http://www.telegraph.co.uk/news/worldnews/middleeast/syria/9512719/Syrian-regime-deploys-deadly-new-weapons-on-rebels.html
Syrian regime deploys deadly new weapons on rebels The Syrian regime has deployed a deadly new home-made weapon in addition to its large arsenal of Russian-supplied armaments – bombs packed inside large oil drums and dropped from helicopters. http://www.telegraph.co.uk/news/worldnews/middleeast/syria/9514698/Syrian-regime-forces-filmed-dropping-barrel-bomb-on-Homs.html

Syrian regime forces filmed dropping 'barrel bomb' on Homs Filled with TNT, oil and chunks of steel, the exploding barrels kill and maim across a wider area than high explosives.

This would certainly seem to fit in what happened here. Barrels full of oil would be prone to catching fire, and TNT just doesn't approve of fire. Tossing them around the inside of an out of control helicopter isn't going to improve the TNT's mood any. After all, the bomb must have some sort of detonator; even if the TNT maintains composure on its own, the detonator might not take to kindly to being smacked around.

This video purports to show a "barrel bomb" being dropped from a chopper in Syria. It's even more craptacular in quality than the first, but you can see a chopper - presumbly the "barrel bomber." It's either Mil Mi-8 or a Mi-24 (I think the latter, due to the stub wings).
https://www.youtube.com/watch?v=53VweYcwLc4

Another video, a collection of "barrel bomb" explosions. These are not trivial blasts, but are instead what you'd expect of a barrel full of TNT.... or what you'd expect of the explosive that turned the original helicopter in this threat into confetti.
https://www.youtube.com/watch?v=sQxvOObQRvQ&feature=related
More:
https://www.youtube.com/watch?v=SeHjxcCF8OU

And in this one, you can actually see the helicopter dropping a barrel which the camera tracks until it passes behind some buildings and explodes.
https://www.youtube.com/watch?v=66u0JxEhA7c

 

[Bill Walker]

On the other hand we have Bill Walker a certified vehicle fire inspector basically agreeing with my conclusion that the explosion is likely caused by fuel and fuel alone (with of course some sort of ignition).

Not exactly. I said (or tried to say) that the fuel/air explosion was probably the last big event, but the exact sequence of events, and all the events involved, are not yet clear. The sources of ignition could include things like RPGs, barrel bombs, and lord knows what else military stuff could be on board - as O.B.B. stated. All this stuff could have cooked off after a small fire inside the cabin, or could have been ignited mechanically as it was flung around the cabin. Or it could have been ignited by gun fire. I bet somebody in the right position would continue small arms fire at the spiralling helicopter. Or, as I said before, the fuel mist could have been ignited by an electrical arc (which also resulted from gunfire damage). It could also be ignited by coming into contact with a hot surface, like a turbine engine or a gearbox damaged by gun fire.

The helicopter obviously has a major yaw control problem prior to the explosion. One could argue a scenario where gun fire punctured fuel tanks or lines, and damaged something in the tail rotor drive train. Nicely mixed fuel/air mist then contacts an overheated bearing or gearbox or driveshaft grinding away against structure. Boom. The overheated bearing scenario, by the way, is a well known ignition source for combustible dust mixtures in farm and forestry machinery. The resulting smoke in those cases has been reported as white, various shades of grey, and black ;D.

I'm not sure about the "hot compressed air" as an ignition source. The only significant source of compressed air is the turbine compressor section, but I'm not sure this produces a high enough air temperature to ignite fuel mist. Turbines I'm familiar with have compressor discharge temps of 200C to 300C, fuel mist probably needs 300C+ to ignite. Feel free to correct me if you have hard facts about Russian compressors. A few inches behind the compressor, however, is burning jet fuel, contained in cans with suitably high surface temps to ignite the fuel mist. And that is before the small arms fire punctures a can and turns it into a crude blow torch. There are lots of possibilities here, but not enough information.

 

[Orionblamblam]

Not exactly. I said (or tried to say) that the fuel/air explosion was probably the last big event, but the exact sequence of events, and all the events involved, are not yet clear.

I think one of the sources of debate is what's causing the bulk of the explosive power. So... have you ever heard of an onboard jet fuel/av gas/kerosene/whatever fire where the fuel alone caused the aircraft to be as wholly obliterated in a single video frame, as happened with this helicopter?

Secondarily: smoke, or column of fuel mist? If you have a vehicle falling from the sky trailing a visible "cloud" of unburned fuel mist, and the vehicle converts to a fireball that lasts as an ingnition source for a few seconds, wouldn't there be at least *some* effort by the flame front to climb up that column of fuel? Hense the "fire breather" photos.

 

[Bill Walker]

I think one of the sources of debate is what's causing the bulk of the explosive power. So... have you ever heard of an onboard jet fuel/av gas/kerosene/whatever fire where the fuel alone caused the aircraft to be as wholly obliterated in a single video frame, as happened with this helicopter?

First, lets agree it is a pretty crappy video. I see big chunks surviving the blast, like a gearbox with at least some rotors attached. I don't see the rest of the airframe, but absence of proof needs is not proof of absence. That is just based on the poor quality of the video, don't get me started on deliberate editing or other tampering. Would this video stand up in a court? Doubt it.

Secondarily: smoke, or column of fuel mist? If you have a vehicle falling from the sky trailing a visible "cloud" of unburned fuel mist, and the vehicle converts to a fireball that lasts as an ingnition source for a few seconds, wouldn't there be at least *some* effort by the flame front to climb up that column of fuel? Hense the "fire breather" photos.

Maybe. If the fuel air ratio is correct. The fuel disperses quite quickly after leaving the vicinity of the aircraft, lowering the fuel to air ratio. If the mixture ratio is below a critical value it may still leave a visible trail, but all the barrel bombs in Syria won't ignite it. (That has just become my new favorite phrase.)

I agree your scenarios are credible, maybe even very credible. I just don't have enough info to rule out other alternative scenarios. Trying to keep an open mind. ;D

 

[Orionblamblam]

First, lets agree it is a pretty crappy video.

Oh, certainly.

I see big chunks surviving the blast, like a gearbox with at least some rotors attached.

I think it's fair to say that a single non-shaped charge explosion that would mulch the transmission would have to be *extremely* powerful... from a few yards away, you'd probably be pushing nuclear. Still, the helicopter is *utterly* destroyed. I've never seen that with rapid deflagration, only with a fairly substantial detonation. I once saw a film of an Aphrodite B-17 suddenly going FOOM in flight; that's the closest visual approximation I've seen to what happend here.

don't get me started on deliberate editing or other tampering.

I'm shocked, SHOCKED to find evidence tampering in the Middle East!

Maybe. If the fuel air ratio is correct. The fuel disperses quite quickly after leaving the vicinity of the aircraft, lowering the fuel to air ratio.

Note that in the video, the smoke/fuel trail hangs around quite a while.