Aviation Fuel - in Use

In Use

"Single-point" redirects here. For other uses, see Single point (disambiguation).

Aviation fuel is often dispensed from a tanker or bowser, which is driven up to parked aircraft and helicopters. Some airports have pumps similar to filling stations up to which aircraft must taxi. Some airports also have permanent piping to parking areas for large aircraft.

Regardless of the method, aviation fuel is transferred to an aircraft via one of two methods: overwing or underwing. Overwing fuelling is used on smaller planes, helicopters, and all piston-engine aircraft. Overwing fuelling is similar to car fuelling — one or more fuel ports are opened and fuel is pumped in with a conventional pump. Underwing fuelling, also called single-point, is used on larger aircraft and for jet fuel exclusively. For single-point fuelling, a high-pressure hose is attached and fuel is pumped in at 40 psi and a maximum of 45 psi for most commercial aircraft. Pressures for military aircraft, especially fighters, range up to 60 psi maximum. Air being displaced in the tanks is usually vented overboard through a single vent on the aircraft. Since there is only one attachment point, fuel distribution between tanks is either automated or it is controlled from a control panel at the fuelling point or in the cockpit. A dead man's switch is also used to control fuel flow. An early use of pressure refuelling was on the de Havilland Comet and Sud Aviation Caravelle.

Because of the danger of confusing the fuel types, a number of precautions are taken to distinguish between avgas and jet fuel beyond clearly marking all containers, vehicles, and piping. Avgas is treated with either a red, green, or blue dye, and is dispensed from nozzles with a diameter of 40 millimetres (49 millimetres in the USA).

The aperture on fuel tanks of piston-engined aircraft cannot be greater than 60 millimetres in diameter. Jet fuel is clear to straw-colored, and is dispensed from a special nozzle called a "J spout" that has a rectangular opening larger than 60 millimetres in diameter, so as not to fit into avgas ports. However, some jet and turbine aircraft, such as some models of the Astar helicopter, have a fuelling port too small for the J spout, and thus require a smaller nozzle to be installed to be refuelled efficiently.