Small Aircraft Jet A powered Crash Worthiness

[nomorecatering]

A question was asked of me which I don't know the answer to.

Typical EFATO situation (typical 4 seat light aircraft) results in controlled low IAS descent into the trees (or forced landing). Fuel tanks are ruptured as the wings come off etc. Is jet fuel less explosive in this situation than avgas. Is there less chance of fire in this event with a Jet A powered diesel aircraft than a typical Avgas powered version.

I would have though that Jet a being a heavier fuel would vaporise less or slower than Avgas resulting in less chance of a fireball.

Anyone got ideas.

[YPJT]

Im no expert but just looking at the differences in flash point between Jet A1 and Avgas makes the avgas look a lot more volatile.
Ignition of Fuels - SKYbrary Aviation Safety (http://www.skybrary.aero/index.php/Ignition_of_Fuels)

[Brian Abraham]

You can stand in a pond of Avtur and drop lighted matches all day without harm, not so with Avgas. In days of yore jets used a wide cut fuel with Avgas like qualities. It was banned for use by the airlines because of its flammability at some point in history, and the safer Avtur products got the tick.

JP-4, which was 50/50 kerosene and gasoline mix, was used by the USAF during Vietnam and they later changed to JP-8, a kerosene, because of JP-4 propensity to ignite.

Demonstration Jet fuel at 1:30, Avgas 9:15

7nL10C7FSbE

[werbil]

You can stand in a pond of Avtur and drop lighted matches all day without harm,

The flash point of Jet A1 is around 38 degrees C at typical sea level conditions. Once the fuel temperature is above this it will go bang just as hard - TWA flight 800 was a classic example of this.

Jet A1 also has a higher energy density per litre, and a significantly lower spontaneous ignition temperature. So if you spill fuel onto a hot surface like an exhaust, without an ignition source Jet A1 will ignite at a lower temperature than AVGAS.

[mikewil]

The fact that refuelling with passengers on board is permitted on some AVTUR aircraft but under no circumstances on AVGAS fuelled aircraft says something about the volatility and safety of a fuel and its propensity to cause a dangerous situation if mishandled.

[megan]

mikewil, because of the relative flash points, Avgas is -40°C, Jet A is 38°C. A 78°C difference. The flash point of a volatile material is the lowest temperature at which vapours of the material will ignite, when given an ignition source. The liquid itself does not burn, it's the vapour it gives off, hence the lower the flash point, the greater the risk.

[mustafagander]

That's the old LAME's party piece. Provided there is a few cm gap to the top of a container of avgas, you can flick butts into it and they go out with a bit of a hiss. Scary to watch first time! Equally, avtur is the same. The reason is that the avgas vapour is way too rich to burn and the avtur way too lean. Unfortunately that horrible JP4 was just right to burn at room temp, hence civvies don't touch it.

[Connedrod]

On a hot day and on a hot tramac jet1 is more dangerous than avgas. Same as oil onto a hot turbo. Oil will flash off and will burn where avgas will trend to evaporate and a fire start from a secondary ignition source.
At the end off the day caution should be used around anything flammable.

There is a term that i cant think of at the moment that explains why avtur is more dangerous on a hot day