(Hollywood Physics) Does Jet Fuel Explode?

Discussion in 'Hangar Flying' started by Aerowerx, Sep 29, 2019.

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  1. Sep 29, 2019 #1

    Aerowerx

    Aerowerx

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    Yes, I know it burns but does it actually explode like gasoline?

    I had fire extinguisher training once, and the instructor had to hold a road flare in the kerosene to get it to even burn. Jet fuel is 2nd cousin to kerosene.

    This morning I was watching the tail end of the Bruce Willis movie "Die Hard 2". The bad guys were getting away in a fully fueled b747, and he had a helicopter drop him off on the 747 wing.

    After the obligatory "wrestling match" with a couple of bad guys he managed to open a fuel dump valve before falling off the wing. He then lit the fuel with his cigarette lighter (in 6 inches of snow, too!!) the flame traveled down the fuel stream on the runway and, just as the b747 was lifting off, traveled up the stream in the air! The b747 then exploded, by which the fire provided landing guidance for the commercial flights that had been on hold (ILS had been destroyed earlier in the movie).

    So, is jet fuel that volatile, or is this a prime example of "Hollywood Physics"? Sometimes I wish I didn't know so much about How Things Work, because it ruins for me an otherwise perfectly entertaining movie!
     
  2. Sep 29, 2019 #2

    Hot Wings

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    Sometimes I wish the wife knew more about how things work so I wouldn't have to sit through these kind of things and then have her be annoyed because "You don't find that interesting?"

    I tend to be too honest..........:oops:
     
  3. Sep 29, 2019 #3

    BJC

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    I don’t know if you classify this as a fire or an explosion:


    BJC
     
  4. Sep 29, 2019 #4

    pictsidhe

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    Hollywood chemistry is particlarly special. Jet fuel does not explode. Airliner fuel tanks do not explode, they are filled with an inert gas after some lightning mishaps. Gasoline needs to be mixed with air in order to explode. Hollywood fuel tanks have additional C4 or TNT or something. I prefer not to put that in my fuel tank.

    There are such things as fuel-air bombs. This is fuel sprayed into the air, then ignitied.
     
  5. Sep 29, 2019 #5

    pictsidhe

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    fire
     
  6. Sep 29, 2019 #6

    TFF

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    It takes a lot to set it off. Jet engine igniters have probably 3-4 times the voltage as a spark plug ignition. Champion use to do a demonstration of putting one drop of jet on a table top ignition demonstrator. The one drop would pop like a firecracker. Jet ignition also is not used once the engine starts so they last forever. Like diesel, a small puddle will probably not light. In a mist, no bets. I have put a propane torch to a small diesel puddle. Nothing happens. If you do get it started which still has a percentage possibility, you are not going to stop it.
     
  7. Sep 29, 2019 #7

    jedi

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    I find it interesting that you even needed to ask!
     
  8. Sep 29, 2019 #8

    Hephaestus

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    Kerosene/diesel hard to light.

    Now throw a quart in a big coffee can, add a roll of toilet paper. Once soaked light the toilet paper - you just built a farm block heater ;)

    It burns, just needs the right conditions to do so.

    That said... When things go boom they go boom
     
  9. Sep 29, 2019 #9

    jedi

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    Looks very similar to Al Haynes landing. Big flames no boom. No flaps for Al. Land at cruising seed.
     
  10. Sep 30, 2019 #10

    Hephaestus

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    Had to look al hynes up, sioux city crash. Remember watching that one on the news when I was young...
     
  11. Sep 30, 2019 #11

    TiPi

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    Simple test: put some kerosene (or diesel) in an empty window cleaner or similar pump spray bottle and aim it at a burning candle. STRONGLY ADVISE TO ONLY DO THAT OUTSIDE IN A CLEAR AREA and keep kids and pets away
     
  12. Sep 30, 2019 #12

    BBerson

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    Last edited: Oct 1, 2019
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  13. Sep 30, 2019 #13

    Aerowerx

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    Maybe so, to all of you, but can it burn faster in 6 inches of snow than the take-off speed of a 747 , and then make the leap from the ground to the wing?o_O
     
  14. Sep 30, 2019 #14

    Hephaestus

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    Quit poking holes in the plot line :) it is a masterpiece. After all it led to the whole Harry Potter series... A bunch of kids chasing Alan Rickman around in a castle.
     
  15. Sep 30, 2019 #15

    Aerowerx

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    Oh, that was only one thing in the movie! There are many others. Like the tower not having a backup transceiver available in the tower? (Everything was remote controlled allowing the bad guys to take control of all radio and navigation systems on the field.)

    And they scrambled the glide slope to put it 200 feet lower? Say what????!!! At that time in history, wasn't the glide slope fixed by the antenna configuration? Not easy to change. That was the only "magic" I saw in the movie.
     
  16. Sep 30, 2019 #16

    litespeed

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    No liquid fuel burns or explodes. Liquids do not burn only the vapour after it converts to gas. However atomised liquid will burn if the droplets are small enough as it can interact with the available oxygen in the air.

    Atomised fuel will burn and when in the correct air ratio it will explode in contact with a ignition source.

    It is the vapour of the fuel that actually burns.

    Anything with oxygen mixed can in theory burn even metal- burning steel wool for example- it is just a high speed oxidation. A explosion is instantaneous combustion of the available fuel.

    No the jet A will not chase the plane like in the movie, but looks good in a movie.

    The aircrash video is not a explosion but a high speed burn of atomised fuel. A explosion would go bang and consume the fuel load in a very very small fraction of a second. Explosions create huge shock waves.
     
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  17. Sep 30, 2019 #17

    Wanttaja

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    I know the man who was the ACTUAL chief of security of both Dulles and National when "Die Hard 2" came out. He Does Not Like the movie.

    Ron Wanttaja
     
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  18. Sep 30, 2019 #18

    Vigilant1

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    Well, there's jet fuel and there's jet fuel. JP-4 was the primary jet fuel used by the USAF from 1951 through 1996, and it had attributes significantly different from Jet A and other military jet fuels (JP-5 as used by the USN at the time and later JP-8 as used by the USN, USAF, and most/all of NATO). JP-4 was considerably more volatile than these other jet fuels, with a flash point of 0 deg F (the other jet fuels generally have flashpoints above 120 F). So, under normal conditions it is possible to set the vapor over a pool of JP-4 alight, but much harder/impossible to light the other jet fuels (or diesel). From a fire safety standpoint, JP-4 was like a mix of kerosene and gasoline. Die Hard 2 was made in 1990, and JP-4 was still in use at that time. Kinda unlikely that civilian 747 would have filled up with USAF JP-4, though.

    Will JP-4 "explode?" Not readily. But, in a mist, it can. And, because of its higher volatility, it is possible, at normal outside temperatures, for JP-4 vapor to accumulate and mix with air into a mixture than can explode.

    The USAF phased out JP-4 in 1996, and now generally uses JP-8. Safer, but messier.
     
  19. Sep 30, 2019 #19

    pictsidhe

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    I've been on the scene of a few car accidents where there has been leaking fuel. Without fail, some halfwit will start panicking about the impending explosion. My standard response is "What, do you think that there is a dynamite in the fuel tank?" To which they always look perplexed. I then tell them that is what is needed for a Hollywood car explosion. But, don't make any sparks, petrol will burn very nicely...
     
  20. Sep 30, 2019 #20

    Rik-

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    As others have said “jet fuel” needs to be atomized in order to burn. I’ve had a PT section explode and the PT blades pierced the fuel tanks. No fire, no nothing other than a hole in the engine and the fuel tank.

    Some of the largest explosions have been due to dust not fuel. Sawdust when blown into the air is very very dangerous.

    Kerosene, JetA , Home heating oil and Diesel #1 are the exact same thing. My fuel supplier said you tell me which you want and I charge accordingly. Of course there is road tax on some and no taxes on the other choices. After buying 2k gallons a week I learned which to ask for really quickly.
     

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