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Ignition of Fuels
From SKYbrary Wiki
| Article Information | ||
|---|---|---|
| Category: | Fire Smoke and Fumes | 
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| Content source: | SKYbrary | 
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| Content control: | EUROCONTROL | 
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| FIRE | |
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| Tag(s) | Post Crash Fire |
Contents |
Definition
The flash point of a volatile liquid is the lowest temperature at which it can vaporize to form an ignitable mixture in air.
Transportation regulations distinguish fuels as either flammable or combustible depending upon their flashpoint. Flammable fuels have a flashpoint below 38°C311.15 K
100.4 °F
560.07 °R. and combustible fuels have a flashpoint above 38°C. As an example, diesel fuel flashpoints range from about 50°C. to around 100°C making it relatively safe to transport and handle. Gasoline, by comparison, has a flashpoint of minus 43°C. Sparks and static electricity can easily ignite gasoline fumes.
Avgas
Aviation fuels fall into two categories, aviation gasoline, commonly shortened as “avgas”, and "jet fuel". Avgas is quite similar to automotive gasoline, except for its octane rating. Octane is the measure of the fuel’s resistance to pre-ignition (the chance of combustion occurring before the spark). The most common form of avgas has an octane rating of 100. The flashpoint of avgas is the same as that of automotive gasoline; thus there is significant danger of combustion if it is not handled carefully. There currently are significantly more aircraft that use avgas than use jet fuel. However, they are generally small GA aircraft that carry only a fraction of the fuel volume of that carried on large commercial jet aircraft.
Jet Fuels
The most common jet fuels in use are named Jet A (U.S.) and Jet A-1 (international). They are kerosene grade fuels with a flashpoint of 38°C. Commercially available Jet B has a lower flashpoint (minus 18°C.) but it also has a much lower freezing point making it very suitable for use in extremely cold environments. Fuels such as JP5 and JP7 have higher flashpoints and were developed to provide additional safety margins in specific military applications. All jet fuels are subject to rigorous testing for impurities and fuels that fail testing are resold for ground applications. All aviation fuels are supplemented with small quantities of additives such as corrosion inhibitors, static dissipaters, anti-freeze, and others.
| Fuel | Flash point | Autoignition temperature |
Freezing point |
| Ethanol (70%) | 16.6°C | 363°C | |
| Gasoline (petrol) | −43°C | 246°C | |
| Diesel | > 62°C | 210°C | |
| Jet fuel | > 38°C | 210°C | |
| Jet A | > 38°C | 210°C | < −40 °C |
| Jet A-1 | > 38°C | 210 °C | < −47 °C |
| JP5 | > 60°C | < −46°C | |
| JP7 | > 60°C | ||
| Jet B | −18°C | ||
| Kerosene | > 38°C – 72°C | 220°C | |
| Biodiesel | > 130 °C |