All machines require an energy source to function, with which they provide a useful output to the operator. A piston-powered airplane uses Avgas, short for aviation gasoline, as aircraft fuel to power its internal combustion engines.
Flight efficiency, operating cost, and the very safety of the passengers, depend on the quality of the fuel with which the engine is being fed. Whether it uses Avgas or Jet fuel, the aircraft fuel system must provide an efficient fuel flow at all flight levels on which the aircraft operates, and in any flight attitude it maintains.
Aviation Fuel: Preferred Properties
Standardized aviation gasoline, used widely throughout the world, retains a number of consistently preferred properties. These properties are also necessary for the use of all aircraft fuel regardless of whether it’s for use in piston engine aircraft or jet airplanes.
- Volatility: Aviation fuel must possess a low volatility. Volatility in aircraft fuel refers to its tendency to vaporize. Fuel that vaporizes too quickly is unsuitable for aircraft.
- Flash point: The volatility of avgas may be low, but it does vaporize to form ignitable vapors. The flash point refers to the lowest temperature at which these vapors would ignite in the presence of an ignition source. For aircraft gasoline, a lower flash point is preferred.
- Fire point: The point at which avgas (in liquid form) would ignite to support a sustained flame, when exposed to an ignition source, is referred to as its fire point.
- Auto ignition temperature: The temperature at which avgas would ignite due to heat alone, without any exposure to an ignition source, is its auto ignition point. Lower auto-ignition properties are, of course, preferred in aviation fuel.
- Fluidity: For use in airplanes, avgas must possess fluidity, or the ability to flow. Fuel possessing higher fluidity is less viscous, and tends to flow freely. Greater fluidity is preferred in plane fuels, since fuels that are viscous in nature would naturally retard or clog the fuel lines.
- Freezing point: As is clear from the term itself, the temperature at which avgas would transform its natural state into a solid is its freezing point. Lower freezing points are preferred for aircraft fuel.
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