wardialer
Posts: 1144
Joined: Fri Sep 14, 2001 1:08 pm

Which Fuel Is More Explosive?

Thu Nov 15, 2001 1:49 pm

I have seen automobile accidents that rarely catch on fire or explode, even in the worse crash. But when I see airplane crashes I instantly see an explosion. Is aviation fuel more explosive than gasoline?
 
Minuteman
Posts: 260
Joined: Sat Aug 05, 2000 1:01 am

RE: Which Fuel Is More Explosive?

Thu Nov 15, 2001 2:11 pm

I know Prebennorholm has a better answer for comparing the flammability of the two fuels, but I'm inclined to guess that gasoline is more explosive just because it seems like its more volatile than kerosene, so you've got a better chance of rapid combustion of vapors.

Cars don't usually burst into flames in a crash because, unlike planes, they don't generally go belching the contents of their fuel tanks on to a hot engine and into the passenger compartment. Of course engineers for both kinds of vehicles try to prevent this from happening, but it seems like the aircraft designer has many more constraints on implementing safety measures than an automotive designer (weight, balance and capacity to name a few).

Just out of curiosity, how many car and plane crashes (non-Hollywood) have you seen? (Personally, I always liked it when the bad guys' car blew up going over the cliff and the Duke boys got away again.)
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Which Fuel Is More Explosive?

Thu Nov 15, 2001 2:24 pm

A few years ago I attended a lecture given by a UK Air Accidents Investigation Branch investigator who said in an a/c accident the fuel atomises due to the deceleration forces which makes ignition easier.

He said he once attended a Jaguar (the aircraft not the car) accident site where they found the instrument panel about 20 ft futher into the ground than the bottom of the crator the a/c left. This was because when the wing hit the ground the fuel atomised and blew up, driving the nose of the aircraft further into the ground.

I guess if you saw a car crash at 300/400 mph they would blow up more easily the an a/c
 
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B737-112
Posts: 829
Joined: Tue Nov 30, 1999 6:01 pm

RE: Which Fuel Is More Explosive?

Thu Nov 15, 2001 4:52 pm

Back when I used to fuel aircraft, I was told by manager there that you could have a gallon bucket of Jet A and drop a match in it and the fuel would actually knock the fire out. I have a feeling that regular gasoline would ignite, it smells much stronger and just seems more volitile.
 
air2gxs
Posts: 1443
Joined: Mon Jun 18, 2001 1:29 pm

RE: Which Fuel Is More Explosive?

Thu Nov 15, 2001 8:42 pm

Car gas tanks are designed not to rupture on impact, for the most part. Also, if they should rupture, the fuel tends not to contact any hot components and the fuel tends not to vaporize.

Aircraft on the other hand will spew fuel everywhere due to the high energy expended in the wreck. The fuel will vaporize and ignite when it encounters a source.

From a chemical stand point, I believe gasoline is easier to ignite than kerosene (jet A)
 
atlamt
Posts: 244
Joined: Thu Sep 13, 2001 12:15 am

RE: Which Fuel Is More Explosive?

Fri Nov 16, 2001 8:55 am

If i remember correctly from A&P school:

At normal temperatures, gasoline in a closed container or tank can give off so much vapor that the fuel/air mixture may be too rich to burn.

Jet A fuel has such a low volatility that at normal temperatures it gives off very little vapor and does not form flammable or explosive fuel/air mixtures.

But when the plane impacts and vaporizes the fuel it is very eaisly ignited.

Also when Jet fuel burns it burns much hotter than gasoline.
Fwd to MCO and Placard
 
Metwrench
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Joined: Fri Aug 17, 2001 11:25 am

RE: Which Fuel Is More Explosive?

Fri Nov 16, 2001 6:05 pm

Consider this. A mid size car weighing 3000 lbs has a maximum capacity of 16 gallons of fuel. That is 3.7 % of the gross weight of the vehicle. One of the commuter turbo props that I work on has a max take off weight of 16,000 lbs with full fuel capacity of 4300 lbs. That is 25 % of the gross weight. That's why there is such a big fire potential. I speculate that the proportions are similar on larger A/C.
 
vc10
Posts: 1352
Joined: Thu Nov 15, 2001 4:13 am

RE: Which Fuel Is More Explosive?

Mon Nov 19, 2001 1:15 am

Atlamt, a good answer. I remember a long time ago a fireman saying it is the fumes that burn not the liquid
 
prebennorholm
Posts: 6447
Joined: Tue Mar 21, 2000 6:25 am

RE: Which Fuel Is More Explosive?

Mon Nov 19, 2001 9:26 am

Very good answers all way.

And Metwrench, long range airliners have max fuel weight compared to MTOW ratio much higher than 25%. An A340-200 has up to 46% fuel. And I think that a Concorde goes over 50%. That's almost comparable to a full tankcar on the road!!!

Regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs

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