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[110]xJammer

Why does your aircraft explode when the fuel tank is on fire?

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Right now if you are on fire you blow up after a dozen or so seconds. I get the idea of fuel fumes blowing up when exposed to flame, but in this case the tank is already burning  and the aircraft is loosing the fuel rapidly too so we know its the fuel that is burning and not wood.

 

Why would there be an explosion then? The fire already consumes most of the oxygen and burns away the fuel, so there won't be any oxygen left in the fuel tank to initiate explosion. Anywhere else in the aircraft wouldn't have enough fuel/vapour to warrant an all-aircraft destroying explosion that we have now.

 

Another reason I could get would be ammo blowing up but I tested and you blow up even with your ammo empty (had a few mg rounds left but that shouldn't matter? it was in the nose of 110 anyway)

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The tank is hit. It leaks. The leaking fuel burns outside the tank. Eventually, the fuel vapour/air mixture inside the tank gets hot enough to ignite. If the fuel vapour/air mixture is within certain limits (about 1.3 to 7.0% vapour by volume) it will ignite explosively. As for what happens outside the tank, I'd not be confident that vapour concentrations couldn't reach the level needed for an explosion. 

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6 hours ago, AndyJWest said:

The tank is hit. It leaks. The leaking fuel burns outside the tank. Eventually, the fuel vapour/air mixture inside the tank gets hot enough to ignite. If the fuel vapour/air mixture is within certain limits (about 1.3 to 7.0% vapour by volume) it will ignite explosively. As for what happens outside the tank, I'd not be confident that vapour concentrations couldn't reach the level needed for an explosion. 

 

This^^

 

Once the air/fuel mixture reaches a flash over point....its BOOM! This can happen if the plane is not burning as well. It happened to me yesterday in a 110 when I was hit by a heavy flak burst from a ship and was not on fire beforehand. My aircraft exploded catastrophically. The only thing left attached to the fuselage was the engines and inside portions of the wings, and my pilot and gunner were insta-killed. Keep in mind this was a day before the DM update, so the effect may be tweaked now, I don't know.

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It might be ammunition that explode aswell. With a good luck I have managed to explode IL-2 to pieces with a couple 20mm shots when hitting ammo box. Has happened couple times in past years 

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10 hours ago, AndyJWest said:

The tank is hit. It leaks. The leaking fuel burns outside the tank. Eventually, the fuel vapour/air mixture inside the tank gets hot enough to ignite. If the fuel vapour/air mixture is within certain limits (about 1.3 to 7.0% vapour by volume) it will ignite explosively. As for what happens outside the tank, I'd not be confident that vapour concentrations couldn't reach the level needed for an explosion. 

 

 

That makes some sense, but I am still not entirely certain why would there be a transition from burning to explosion. Wouldn't petrol effectively smoulder inside of the tank due to high temperature and oxygen poor atmosphere and thus depleting the oxygen in the tank? My assumption here is that we have burning -> explosion transition, instead of pre-ignition fuel -> explosion. And the argument that the burning is only outside of the tank makes me question how then the internal fuel blows up due to outside burning, but does not smoulder/etc due to outside burning as the fuel/air ratio is slowly changing towards explosion.

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I'm not by any means an expert here but my understanding is that fuel tends not to explode under normal circumstances but rather when you introduce enough oxygen into the mixture. A full fuel tank won't actually explode all that easily... it's a half empty one with fuel vapours (and say a leak) that once it reaches a critical level has the chance of exploding.

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saw a documentary about bodenplatte recently where some Crazy p47 pilot sticks around in a dogfight with his right wing in fire. Think he even managed to land safely. If I were in his shoes I think I would most very probably have bailed just as I tend to in IL2 lol.

Edited by =11=Herne

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5 minutes ago, ShamrockOneFive said:

I'm not by any means an expert here but my understanding is that fuel tends not to explode under normal circumstances but rather when you introduce enough oxygen into the mixture. A full fuel tank won't actually explode all that easily... it's a half empty one with fuel vapours (and say a leak) that once it reaches a critical level has the chance of exploding.


Indeed, and add to this mix the fact that some planes had exhaust gases pumped into the tanks, putting them in surpression and removing at the same time the air (oxygen) and most of them were also self sealing, to make a tank explode you'll need to tear it apart, making holes big enough so it can't seal and the exhaust gases have no effect allowing enough air to enter the tank and create the explosive mix.

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1 hour ago, xJammer said:

 

...Wouldn't petrol effectively smoulder inside of the tank due to high temperature and oxygen poor atmosphere and thus depleting the oxygen in the tank?

...

 

It can't smoulder until it is alight. As I've already said, the fire may be external. If the mix in the tank is right, as soon as it reaches self-ignition temperature (about 260° C) it will explode.

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1 hour ago, ShamrockOneFive said:

it's a half empty one with fuel vapours

It's actually almost empty ones. Half empty still tend to produce overly rich gas mixtures.

 

A little story about that: when the Me-323 ferried fuel barrels across to Tunis, then the way there was just bad, because in case of enemy fire they knew they would go up in flames. But the way back, loaded with empty drums gave them horrors. One shot in these drums containing nothing but an explosive fuel air mixture (mind you, that pump doesn't *completely* vacate the barrel) would make them blow up in a way that would preclude the use of a parachute.

 

Same with burning cars. They only explode in the movies. That bang that you hear are the tyres busting. But the tank hardly ever explodes. It just burns. Even 15% fill is too much to let it go with a bang.

Edited by ZachariasX
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Emptier the tank, higher the probability it will explode when under fire (or in contact with flames). Also explosion will be deadlier on average (due to bigger amount of explosive mixture).

 

Interestingly, chemical explosive mixtures are usually somewhat analoguous to nuclear explosion, or a supernova if you will. Nothing happens till certain parameters are met (mixture %, critical mass,...) and then all of a sudden - booom. 

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This is when you should really start worrying about explosions:

 

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My two cents worth.  You could have two scenarios.

 

1) An explosive cannon round or tracer/incendiary MG round penetrates the tank and ignites the fuel vapor in the tank resulting in an immediate explosion. 

 

2) A round (more likely an MG round) penetrates the tank and starts a fuel leak that may be ignited by a subsequent round with an ignition source.  The fire in the fuel leak stream may have to burn upstream against the force of the slipstream, which may be enough to slow it reaching the tank (lots of stories of pilots diving their aircraft to high speeds to blow the fire out).  If it does reach the tank it has to penetrate the opening which might be small and partially closed by self-sealing (hence the reason for self-sealing).  Then if the fire does enter the tank it ignites the vapor and the tank explodes.

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I cant say if that happens ingame, but in RL you also have to take into acount that the plane is moving, so the fuel+air inside the tank will be displacing all around and thus the "will it blow in this configuration?" factor probably changes from second to second.

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also can fires be put out? Seen a video (if my memory does not fail me) where a 111 was on fire in game and with diving (and perhaps cutting the flaming engine) it managed to put out the fire. With the bodenplatte planes this might be a tactic to be used, if our fights will take place at higher altitudes anyway.

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2 minutes ago, E4GLEyE said:

also can fires be put out? Seen a video (if my memory does not fail me) where a 111 was on fire in game and with diving (and perhaps cutting the flaming engine) it managed to put out the fire. With the bodenplatte planes this might be a tactic to be used, if our fights will take place at higher altitudes anyway.

Yes I've put out fires by diving quickly, it can be done if you've got enough altitude.

Better bet is to bail out though.

 

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@307_Tomcat This is a fuel fire, not an explosion.

 

35 minutes ago, Georgio said:

This is when you should really start worrying about explosions: 

No, this is when you should worry about 700 tons of Sodiumcyanide (that we know of) that went up as well.

 

About the 1300 tons of sodiom-, ammonium-, and potassiumnitrate (that we know of), there is not too much to worry about. You were either bown top bits (no time to worry) or not (worry abput the poison that's gonna rain down on you. Tianjin, 2015. Chinese have a special relationship with firework, indeed. But the gold standard for blowing up your harbor is still Canadian.

 

 

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26 minutes ago, 307_Tomcat said:

 

Please watch to the the end of the video.  

I did. This plume is what‘s happening if you are setting a lot of fuel on fire. These are indeed gases that go up in flames, and because combustion is so fast (still overly rich mixture, hence not a detonation) the fireball gets lifted up by it‘s own thermal. But it is nothing like an explosion you get when mixture is „correct“.

 

But it is still impressive.

 

I well rembember when near where we lived a couple of railroad gasoline cars derailed and 5 of them broke up and caught fire. Was many times the fire of that unfortunate accident you posted. And there, there were explosions, clear enough to be differentiated by any layman from the huge fireball. A lot of that fuel spilled in the drains and filled the entire drainage sytem with fuel vapors and gasoline. It gave the bystanders the creep of their lives when suddenly with a kaboom the entire sewage system over hundreds of meters seemed to explode at once, shooting those large, heavy iron manhole covers high up in the sky simultanously, smashing cars and structure. That kaboom had very little fire. But it convinced a huge crowd „to move on, as there is absolutely nothing to see“, as opposed to the large fire.

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4 hours ago, E4GLEyE said:

also can fires be put out? Seen a video (if my memory does not fail me) where a 111 was on fire in game and with diving (and perhaps cutting the flaming engine) it managed to put out the fire. With the bodenplatte planes this might be a tactic to be used, if our fights will take place at higher altitudes anyway.

 

I've managed to put out a fire once by diving and turning the engine off; the engine even came back on too as a bonus for me. I think it was in a MiG or a LaGG but I can't remember exactly. It was an engine fire, not a fuel tank fire though. I've never been able to put a tank fire out in game and don't know that I have seen anyone else do it either.

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On 1/15/2019 at 3:16 PM, Disarray said:

 

I've managed to put out a fire once by diving and turning the engine off; the engine even came back on too as a bonus for me. I think it was in a MiG or a LaGG but I can't remember exactly. It was an engine fire, not a fuel tank fire though. I've never been able to put a tank fire out in game and don't know that I have seen anyone else do it either.


I haven't been able to put out a single fire since they re-worked the system last year, even straight dives from 10,000m during testing with HE-111's always end up with my aircraft ripping itself apart with the flames still present at over 800kph, and persist until the airframe explodes and lawn darts into the ground well past 900kph. Same result with PE-2's, 109's, 110's, P-47's, the list grinds on.

It's beyond annoying engaging bombers at high altitude and being forced to bail out after a fuel tank catches on a lucky shot because of this broken mechanic.

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On 12/6/2018 at 12:54 PM, ZachariasX said:

Same with burning cars. They only explode in the movies. That bang that you hear are the tyres busting. But the tank hardly ever explodes. It just burns. Even 15% fill is too much to let it go with a bang.

 

Not true.  I set a few cars alight in my youth and there does come a point where they explode.  Perhaps not like a TNT explosion but I daresay if it happened in an aircraft wing it would be enough to break it off and if it happened in the fuselage it would certainly kill the pilot instantly and turn the plane into a fireball.    The ones I did were probably low on fuel but after a leak that may be the case with burning aircraft.    They did have self sealing tanks and did pump in inert gases (you can see this in the startup animation) but that just explains how we can often fly home trailing fuel without ever catching fire.  Other times the damage would have been too much and the inert gases would have escaped.

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3 hours ago, 56RAF_Roblex said:

Not true.  I set a few cars alight in my youth and there does come a point where they explode

Fuel has a very high specific energy. If it was a detonation, keep in mind that gasoline has more ten times the specific energy than TNT. Even if the car was set on fire with just a gallon of fuel in there, it would be enough to send it sky high. I doubt that was what you witnessed. But even deflagrations can be impressive. No doubt. Fuel on fire is... problem.

 

In real aircraft, one has to keep in mind that aluminum burns very, very well next to a fuel fire. Also, leaking fuel can enter other compartments of the aircraft where it can form an explosive mixture and explode, blasting the crate to bits or „just“ burn there, shielded from the air current.

 

I can‘t really think of worse than a fire on board.

 

 

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This year will be my 23rd year as a professional firefighter at a city station. I've been to a lot of car fires. If I had to guess,  I'd say I've been to over 50. In that time I've seen shock absorbers pop,  gas struts blow & tires burst.  I've seen jets of flames coming out of petrol fillers. I've had plastic tanks give way dumping their contents.  What I've never ever had is a fuel tank explode. 

 

Why?  Because fuel is not an explosive. An explosive must have a self contained supply of oxygen.  Fuel doesn't. It can burn if given oxygen & an ignition source.  It can even detonate if fuel vapours are mixed with air but liquid fuel will never explode.  Ever.  Full stop. 

 

I once attended an incident where a gent was cutting the top off an empty 44 gallon drum with oxy acetylene. He'd rinsed out the drum before hand but there was still enough residue fuel vapour to cause a detonation and rip half the lid off.  He was pretty badly concussed.  But on an explosive scale, it was pathetic. The amount of fuel found as a vapour within the drum would have only been grams. Grams will not blow a fighter apart. 

 

If this had been the fuel air mixture in a partially empty aircraft fuel tank,  my guess is it would have burst the tank dumping the now burning remaining fuel into the fuselage, turning the aircraft into a massive fireball. 

 

On a side note, while fuel won't explode because it lacks oxygen, hitting the oxygen bottle of a burning fighter must have caused a massive boom! 

Edited by Bloodsplatter
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To make 1 kg fuel explode, you require 14 kg air, this means a can of 12 cubic meters. 

 

To make this 200 l fuel drum explode

Spoiler

Drum_(container).jpg

 you can put in not much more than 1.7 deciliters 17 grams (edit: ~2 cl) of fuel.

 

On other words, it only explodes when you got out evetything you reasonably can. If you have more in, you will have a conflagration and a nice fireball when fuel is sprinkled around.

 

The empty can is bad. If its less fuel than the 2 cl, then you‘ll have the drum partially full with an explosive mixture.

Edited by ZachariasX

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Do not try this at home.  In fact do not try it anywhere.  Throw some gasoline on a campfire.  I speak from experience.

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