Fuel
AvGas vs Jet Fuel
Similar to gas cars vs diesel cars, aircraft fuel falls into roughly 2 categories: AvGas and Jet Fuel.
| AvGas | Jet Fuel | |
|---|---|---|
| Engine | Piston (AvGas) | Piston (Diesel) / Turboprop / Jet |
| Price | More expensive | Cheaper |
| Availability | Limited | Widely available |
AvGas
High-octane gasoline, piston-engine powered aircraft. AvGas is similar to car gas, but still with lead. Unleaded options are coming.
- 100LL: The most common in US is 100LL, where "LL" means "low lead". The availability is limited, especially outside of north america.
- UL94: a 94 octane unleaded avgas. Only available in select airports. Swift Fuels. https://www.swiftfuelsavgas.com/
- G100UL: approved in 2022. General Aviation Modifications, Inc. (GAMI). https://www.g100ul.com/
Unleaded vs 100LL: Unleaded has higher fuel price, lower maintenance cost (due to a cleaner fuel burn, no deposits, and no fouled plugs).
Why lead? In many piston engines, lead in avgas prevents damaging detonation that can result in a sudden engine failure. For general aviation aircraft that need 100-octane fuel to prevent detonation.
Lead poisoning is caused by exposure to high levels of lead. Lead is most commonly found in houses built before 1978.
Fuel grades (octane): how much compression can they take without detonation.
Jet Fuel
Jet Fuel is a highly refined Kerosene, ignited by pressure and heat; cheaper, more available, and can run in diesel engines.
Low-octane. Jet A and Jet A-1, for gas-turbine engines. Most jet fuels in use since the end of World War II are kerosene-based.
- Jet A: only in US and a few Canada airports, freezing point is −40 °C (−40 °F)
- Jet A-1: in the rest of the world other than the former Soviet states, freezing point is −47 °C (−53 °F), lower than Jet A
- Jet B: enhanced cold-weather performance, freezing point is −60 °C (−76 °F)
Jet and gas turbine (turboprop, helicopter) aircraft engines typically use lower cost fuels with higher flash points, which are less flammable and therefore safer to transport and handle.
Jet fuel is very similar to diesel fuel, and in some cases, may be burned in diesel engines. Avgas is leaded, so some small general aviation piston engine aircraft are equipped with diesel engines to use jet fuel. A diesel engine may also potentially be more environmentally friendly and fuel-efficient than an avgas engine.
Kerosene vs Diesel
Kerosene is extracted from crude oil first, then diesel, as kerosene has a lower boiling point than diesel.
Diesel is a reddish colour while kerosene is colourless
Kerosene is typically cheaper than diesel, and it burns at a lower temperature than diesel which prevents gelling in freezing temperatures,