The ultimate guide to jet and aviation fuel
Jet fuel is relied on by airlines and passengers across the globe, but have you ever wanted to know more about this incredibly important form of energy? In this ultimate guide to jet and aviation fuel, we explore what jet and aviation fuel are, their differences, properties, the various types of jet fuel available, plus much more.
Jet fuel is used to power jet engines. Also known as aviation turbine fuel or Avtur, it is a highly refined Kerosene (a type of diesel), ignited by pressure and heat.
There are many different specialised types of jet fuel, including those designed for passenger aircraft such as JET A-1, through to military-grade fuels such as JET F-34/JP-8.
Each has different characteristics, including freezing points, octane ratings and additives.
Aviation fuel is a term often used interchangeably with jet fuel but can also refer to aviation-grade gasoline used for general aviation; piston propeller engines, microlights and sports aircraft, for example.
Known as AVGAS, this spark-ignited fuel has a much lower flashpoint than jet fuel and a much higher octane rating than the petrol used in road vehicles.
Aviation fuel comprises long strings of hydrocarbons which are derived from the refining process. It is extremely difficult to say exactly which hydrocarbons are used in aviation fuel as the composition varies considerably based on the source petroleum.
In simple terms, the key differences between aviation fuels and petrol is that aviation fuel is much purer, and jet fuel comprises different hydrocarbons. For instance, when planes are airborne, temperatures can drop to around -40˚C. At this level, automotive petrol would freeze, but since jet fuel is a type of kerosene with a much lower freezing point, it remains liquid.
Additionally, while AVGAS and standard petrol feature performance-enhancing additives, such as those used to improve fuel performance, some are only found in aviation fuel, such as metal deactivators, gum inhibitors and static dissipaters.
At normal temperatures, aviation fuel gives off very little vapour. This means it doesn’t ignite easily and or form dangerous fuel-air mixtures.
JET-A1, also has a flash point higher than 38˚C – crucial, as it makes the fuel less likely to combust unsafely. Once vaporised, however, jet fuel is extremely flammable and burns at a much higher temperature than other fuels.
The freezing point of Jet A is -40˚C, while the freezing point of Jet A-1 is -47˚C. AVGAS, on the other hand, can have freezing points around -58˚C.
It’s important that water is never added to aviation fuel and every effort should be made to isolate the two.
This is because when flying at altitude, extremely low temperatures can cause any water present to freeze, potentially blocking the aircraft’s fuel inlet pipes. To combat this, fuel heaters are often used to prevent any water in the fuel from freezing.
The octane ratings of AVGAS, a gasoline-based fuel, are usually either 91 or 100 (lean mixture) and 96 or 130 (rich mixture). The octane rating of jet fuel is much lower, around 15 – this is much more like automotive diesel and thus much more resistant to detonating due to sparks or compression.
Aviation fuels are available for a wide range of aircraft.
- AVGAS UL91 – Colourless and unleaded piston engine fuel that’s safer for the environment, AVGAS UL91 is designed for sports and general aviation aircraft.
- AVGAS 100LL – A high-quality, low-lead piston engine aviation fuel used for more taxing flying, such as aerobatics.
- JET A-1 – The world’s most common fuel for jet turbine engines, JET A-1 can also be used in diesel general aviation aeroplanes.
- JET F-34/JP-8 – A military-grade turbine engine fuel, designed for use in aircraft and helicopters that lack fuel system heaters.
According to Statista, commercial airlines are forecast to use 97 billion gallons (441 billion litres) of fuel in 2019. When just looking at Total’s aviation fuels, an aircraft is refuelled with our JET A-1, AVGAS 100LL or AVGAS UL91 fuels every 30 seconds on average.