Exploding fuel tanks.

[Bullets]

As rare as people say setting someone up in flames is I have always found one certainty in the situation, shortly after being set aflame that section that is on fire will explode 100% of the time. What is the accuracy of this? I could understand if it was the fire/heat igniting nearby ammunition reserves however it is not always the case.

 

I was flying in a pe2 returning to base and I was bounced and I ended up with my wing on fire quite near the tip of the wing. I guessed it was that wings fuel tank had been hit and was just going to flame away and potentially not explode as there was nothing I could see that would cause an explosion, it would just stay on fire until that fuel tank had run out of fuel. I was mistaken however as when I was high tailing it to the nearest airfield my wing exploded and I ended up making a nicely sized crater in the ground.

 

Anyway the point is what is peoples opinions and whats the accuracy on exploding fuel tanks every time they are set on fire?? 

 

Included a photo of Ivan sat wondering how much trouble he is going to be in   

[216th_Lucas_From_Hell]

The simple explanation: https://www.quora.com/Does-a-fully-filled-petrol-tank-really-lead-to-an-explosion-when-its-exposed-to-high-temperatures

[=362nd_FS=Hiromachi]

It's reasonable, once set afire fuel tank can extinguish itself in some rare occasions (sometimes due to high speed the air stream over the wing managed to put it out) or by some measures like carbon dioxide fire extinguishers (either hand operated or automatic). But first case depends on luck and latter one on usage of such CO₂ system. If you are out of luck and your fuel tanks do not have any fire protection systems than your most likely done (if there was time I'd immediately land aircraft). 

Fuel tank filled with gasoline, once exposed to oxygen and ignited will "cook" until certain temperature is reached at which spontaneous explosion occurs - this can be divided into detonation (supersonic shock wave) or deflragration (sub-sonic shock wave).

[Bullets]

What about if your fuel in that tank runs out before it reaches the "cooking/exploding" temperature?  Thanks for the explanation though makes more sense!   However how would fuel (inside a tank) with no oxygen in no matter the temperature explode if there is no oxygen? 

The simple explanation: https://www.quora.com/Does-a-fully-filled-petrol-tank-really-lead-to-an-explosion-when-its-exposed-to-high-temperatures

Ah so you are saying that as the fuel runs out air fills the fuel tank and then the flames essentially move into the fuel tank and explode the remaining fuel inside the tank? 

[216th_Jordan]

Can't check what lukas said right now but the lesser fuel there is in a tank the more likely it is to instantly explode. You need quite some oxygen for the fuel fumes to ignite exlosively. Apart from that: What Hiromachi said.

 

You can outdive a fire with a high speed dive and sideslip. I did it quite some times in the Pe-2.

Edited November 11, 2016 by 216th_Jordan

[TP_Silk]

I would assume that the empty fumes left in a tank would be more likely to explode due to naked flame than the liquid fuel would be. Maybe my physics is incorrect though.

[=362nd_FS=Hiromachi]

 

 

What about if your fuel in that tank runs out before it reaches the "cooking/exploding" temperature?

It was found during various tests and trials that even emptied fuel tanks still contain some small remains of fuel at the bottom and are filled with fumes. Some aircraft utilized systems that transferred part of the exhaust gases produced by engines to fuel tanks which would vastly lower chance of ignition, other aircraft had CO₂ pumped continuously as fuel quantity in tank was decreasing. 

Also, its not easy to give a precise answer to your question because sometimes chain reaction leading to explosion was so quick that all three phases (ignition -> smoke -> flame) happened almost simultaneously and one would not notice that. 

 

 

 

However how would fuel (inside a tank) with no oxygen in no matter the temperature explode if there is no oxygen? 

Well, its rather obvious, the very moment fuel tank is being pierced or damaged it is being exposed to atmosphere outside. While fuel is leaking, tank is also filling with air.

 

 

 

You need quite some oxygen for the fuel fumes to ignite exlosively.

Actually, for a fire itself, an atmosphere containing 16% oxygen will support fire. Earths normal atmospheric oxygen content is somewhere around 20% if I remember from school.  

 

 

 

You can outdive a fire with a high speed dive and sideslip. I did it quite some times in the Pe-2.

Hmm, you roll over, go into a steep dive and also hit rudder to create sideslip ? Havent tried that one. Thanks for the tip Jordan. 

[Czar66]

I would assume that the empty fumes left in a tank would be more likely to explode due to naked flame than the liquid fuel would be. Maybe my physics is incorrect though.

Liquid fuel of any kind does not ignite. Is it's gas that does so. They do evaporate constantly.

[seafireliv]

Whenever something catches fire, if I can`t put it out in 5 seconds, I jump.

[216th_Jordan]

 

Hmm, you roll over, go into a steep dive and also hit rudder to create sideslip ? Havent tried that one. Thanks for the tip Jordan. 

 

Going fast alone can also just stop your fire, but make sure to dive immediately when on fire. Also you need to be really fast, sometimes near sturctural integrity speed limit. I have not tried sideslip extensively but I remember a dev saying that by sideslipping fires are easier to be extinguished. But of course there are also fires which are not extinguishable.

[Lusekofte]

If the plane have self sealing tanks there are other reasons for a explosion than the hit on the tank. Fire and severe overheating of the tank make it burst allowing correct mix of oxygen and fuel gas. A close to empty tank will do the same, it is the heat and expansion of tank, not the mix of flammable substances and oxygen in the tank that is the problem, that mix is too fat.

[III/JG52_Otto_-I-]

Russian fighter were have a wood-built structure, and the risk of fire was important , but Russian designers equipped his airplanes with a flammability reduction system.

Basically the exhaust gases (CO and CO2 ) were filtered and pumped inside the fuel tank, displacing the oxigen. 
This system prevented the tanks from catching fire on when it was hitting with small caliber bullets. ...But This is not effective when the tank is hitted by 20mm explosive bullets, who ripped one square feet of the tank, spraying  the fuel in the airstream.

 

Only when fuel tank is not hitted by cannon bullets the aircraft can survive.

[216th_Lucas_From_Hell]

To complement Otto's post, you can see that system in the MiG-3 close to the nose. There are two small pipes leading from the engine into the fuel tanks.

 

The phenol used to impregnate the wood in some aircraft (Lavochkins for example) also prevented the structure itself from catching fire, but fuel remains fuel.

[-=PHX=-SuperEtendard]

I would assume that the empty fumes left in a tank would be more likely to explode due to naked flame than the liquid fuel would be. Maybe my physics is incorrect though.

 

Yep, it's basically this.