Why is fuel used in airplanes different from those used in motor vehicles?

 Aviation turbine fuels are used for powering jet and turbo-prop engine aircraft. Kerosene was used to fuel the first turbine engines. Kerosene-type fuel was chosen as having the best combination of properties. 

As the primary function of aviation turbine fuel (jet fuel) is to power an aircraft, energy content and combustion quality are key fuel performance properties. Other significant performance properties are stability, lubricity, fluidity, volatility, non-corrosivity, and cleanliness. Besides providing a source of energy, fuel is also used as a hydraulic fluid in engine control systems and as a coolant for certain fuel system components.

However, compared to a kerosene-type fuel, other type fuels like used in motor vehicles were found to have operational disadvantages due to their higher volatility:

• Greater losses due to evaporation at high altitudes
•  Greater risk of fire during handling on the ground
•  Crashes of planes fuelled with wide-cut fuel were less survivable
•  Lighter (less dense) fuels, such as gasoline, have higher heating values on a weight basis: whereas heavier (more dense) fuels, like diesel, have higher heating values on a volume basis. Since space is at a premium in most aircraft, the amount of energy contained in a give quantity of fuel is important. A fuel with high volumetric energy content maximises the energy that can be stored in a fixed volume and thus provides the longest flight range.

There are currently two main grades of turbine fuel in use in civil commercial aviation: jet A-1 and jet A, both are kerosene type fuels. There is another grade of jet fuel, jet B which is a wide cut kerosene (a blend of gasoline and kerosene) but it is rarely used except in very cold climates.

Jet A-1 is a kerosene grade of fuel suitable for most turbine engine aircraft. It is produced to a stringent internationally agreed standard, has a flash point above 38 degrees centigrade (100 degrees Fahrenheit) and a freeze point maximum of minus 47 degrees Centigrade.

Jet A is a similar kerosene type of fuel, produced and normally only available in the U.S. It has the same flash point as Jet A-1 but a higher maximum freeze point (minus 40 degrees centigrade).

Jet B is a distillate covering the naphtha and kerosene fractions. It can be used as an alternative to jet A-1 but because it is more difficult to handle (higher flammability), there is only significant demand in very cold climates where its better cold weather performance is important. Courtesy : The Hindu