why do planes explode instantly when they crash?

Question

like with cars teh gas leaks and the combust but i dont get why planes instantly explode. is it the force that makes the gas combust or is it have something do do with the combustion in the engine.

Answer 1

Okay, so I read some of the first several answers people have written to you for your question, and every single one of them is wrong, some of the later answers are partially correct, but have some incorrected details, and I beleive one individual other then myself had a fully correct answer for you. Take it from a FAA licensed Aircraft Aviation Maintenance Technician, I've been doing this stuff for 6 years now.
First of all the planes doesn't explode, it is a rapid flame front (and actually most plane crashes don't result in a fiery wreck, only very few do). Explosions have bright flashers, if you watch a plane erupting into flames during an accident you'll notice that the flames and smoke have a slow roll to them (rapid to the untrained eyes, but trust me, professionally speaking it is a slow roll).
Okay now for the fuel. Gasoline that you burn in your car is much more volatile then diesel and kerosene (the two fuels that just happen to be jet fuel). Kerosene is known as Jet A or JP-4, and Jet B or JP-5, and JP-8 is your diesel grade of jet fuel minus sulfurs and detergents and dies that you find in your diesel that you buy at the fuel pump. It takes higher temperatures to ignite these fuels. A simple spark from a spark plug isn't hot enough to get these to ignite, unlike the gasoline in your car's engine.
Liquid fuels are not explosive nor flammable, only the fumes are flammable, but not explosive (to become explosive in nature, it has to be a fault inside a man made environment). Gasoline is your most volatile because it most readily vaporizes, it has a vapor pressure of around 14psig (pounds per square inch gauge). Diesel or your JP-8 has a vapor pressure around 8psig, and then your kerosene Jet A and Jet B or also know as JP-4 and -5 have an psig of some where between 3 to 6 (I can't remember exactly, but it is within this range). Also commonly, the higher a fuel's vapor pressure, the lower the flash point is (point at which it will begin to support burning or a flame front).
Also, in order for that jet to have what you refer to as an explosive fiery wreck (although it isn't), the fuel tanks (wings) must be compromise (broken open so the fumes can escape) and the burner section of the engine needs to still be burning when the engine’s combustion chamber is compromise, or other hot surface (roughly 2000 degrees fahrenheit in order to witness the flaming jet wrecks you'll witness (which when accidents do happen this rarely happens). That means a very violent wreck has occurred if your witnessing this type of devastation, example, September 9th, 2001. Because any sparking from any wires, including high current load wires, won't produce enough heat to ignite the jet fuel which is much less volatile then gasoline. Check out the FAA's web page, you can research all documented plane wrecks for yourself, and you'll see the majority of them had no violent fires there to speak of.

Note (added 02May2007) For those who have given this answer thumbs down, please do a little research on fuel and espeacially aviation and jet fuels. You gave a true honest educated answer 3 thumbs down from your own ignorance and lack of knowledge, and could be responsible for leading the individual asking this question incorrect information.

Answer 2

A suv can contain about 23-27gallons of gasoline. A modern 747 can hold 63705 gallons of Jet A-1 fuel. Jet fuel is much more explosive than gasoline and as a plane crashes, I could bet that all that twisted metal creates some sort of spark. Also the fuel is contained within the wing and undersection of the aircraft, unlike a car which has the tank fitted on the bottom of the car. A plane will crash with alot more force than a car. Just look at the aftermath of a plane crash. The fuel would be instantly dispersed across the wreakage area.

Answer 3

To ALL the people saying that "airplane fuel is more volitatile than car fuel"... If the aircraft is powered by 100LL aviation gasoline (light planes), the fuel is similar in volatility though by octane rating would be MORE DIFFICULT to combust. If the plane is powered by "jet fuel" or JET A this fuel is like Kerosene and has a hig flash point and burns much more slowly than gasoline! Go pour both on the sidewalk, light one then the other. Make sure you stand back with the gasoline!

Answer 4

You are all very very wrong.

Jet fuel is much less volatile than auto fuel. Even Av gas is "slower burning" than regular pump gas. The slower burn rate is actually better for the engines.

http://en.wikipedia.org/wiki/Avgas

But in airliners (which I think is what you are looking for) it happens like a fuel-air bomb. The airframe looses its integrity and integral fuel tanks come apart at the seams (literally). The fuel becomes air-born (as it was travel several hundreds of miles per hour and wants to stay moving). The fuel reaches a vapor-like state and will usually get ignited by the engines which also loose their integrity and also don't have flame arrests to keep the flames from getting in contact with the now vaporous fuel.

It works tragically too well. If you would just hold a match under the wing-tank of a non-moving plane and punch a hole in it the fuel would simply extinguish the match. If you shoot a hole in the tank with a bullet it will simply rip a hole in it and not ignite. It is only when you vaporize the fuel first and then introduce an open ignition source do you have a disaster.

Gas explosions in general aviation are extremely rare now days. But gas will vaporize on its own and back in the days of PBY's and flight crews that smoke cigarettes often they would explode for no apparent reason.

Answer 5

The answer is simple:

1. Why do planes explode instantly when they crash? Because planes are not crash tested

2. Why are planes not crash tested? Because planes can't pass the crash test.

3. Why can't planes pass the crash test? Because every plane designed to pass the crash test could not carry enough passengers to make a profit.

4. Why couldn't the planes carry enough passengers to make a profit? Because the new crash protection features took away too much passenger space.

5. What was the solution? Drop the crash test requirement.

Answer 6

Piston engined aircraft typically use 100/130 octane that is not much more volatile that auto fuel. Jet aircraft use a fuel very much like kerosene that has very low volatility. An explosion is generally the result of a high impact, high angle uncontrolled crash which bursts the fuel tanks and vaporizes the fuel, mixing it with air. An electrical or metal on metal spark is enough to ignite the resultant air/fuel mixture.

A low agle controlled forced landing, where the pilot has the opportunity to turn off the electrical system and minimize the impact does not usually result in an explosion.

Answer 7

They don't all explode instantly. Some don't explode at all.

Some do, it all depends on the severity of the crash and other circumstances. There are many aircraft that "crash" without evening caching fire. There are numerous accidents and incidents each year where an aircraft will go off the runway on landing or sometimes on take-off.

Southwest has had two accidents where their 737s have slid off the end of a runway, once at Burbank and the other in Chicago, neither one caught fire but there was significant damage both times.

Air France had an aircraft that went off the runway in Toronto and all the passengers and crew were able to get off that aircraft before it caught fire.

Answer 8

Not all crashes result in an explosion, and unlike the over-dramatized stuff you've seen on television, explosions are not always instantaneous. Instant explosions are for bombs.

Aviation jet fuels are generally LESS volatile than automotive gasoline. Nevertheless, crash-related explosions occur for a couple reasons.
1) the volume of fuel carried onboard an airliner or military aircraft is significantly greater than in an automobile, and
2) there are multiple ignition sources; these include the jet engines themselves, plus any hot kitchen equipment, plus aux. power unit. A four-engine airliner has potentially six ignition sites all slamming into a huge pool of fuel.

Answer 9

First, there's relatively more fuel on an airplane than in a car, compared to the size of the vehicle. At takeoff, most of the wings of an aircraft are filled with fuel -- and the wings make up a significant portion of the entire structure of the craft. By contrast, the fuel tank on a car is a relatively small portion of the structure.

Second, aircraft fuel is much more volitile than automobile fuel.

Third, a violent airplane crash is much more likely to destroy the fuel tanks (wings) than a crash in a car is to damage the fuel tank (tank in bottom rear of most cars, more protected (by design)).

Answer 10

Its the amount of fuel in the tanks. Also, the fuel is different than car fuel. It is much more explosive. The crunching of metal creates mega sparks which ignite the fumes of the gas and you get a chain reaction explosion.

Who's giving all the thumbs down? Stupid retards. You people don't even know the truth. I can't even believe that humans can be so low. I am smarter than everyone on here.