Product Code Database
Aviation fuels are petroleum-based , or petroleum and synthetic fuel blends, used to power aircraft. They have more stringent requirements than fuels used for ground use, such as heating and road transport, and contain additives to enhance or maintain properties important to fuel performance or handling. They are kerosene-based (JP-8 and Jet A-1) used in gas-turbine–powered aircraft. Piston-engined aircraft use leaded gasoline and those with diesel engines may use jet fuel (kerosene). By 2012, all aircraft operated by the U.S. Air Force had been certified to use a 50–50 blend of kerosene and synthetic fuel derived from coal or natural gas to stabilize the cost of fuel.
Jet-A powers modern commercial airliners and is a mix of extremely refined kerosene and burns at temperatures at or above . Kerosene-based fuel has a much higher flash point than gasoline-based fuel, meaning that it requires significantly higher temperature to ignite. It is a high-quality fuel; if it fails the purity and other quality tests for use on jet aircraft, it is sold to ground-based users with less demanding requirements, such as railroads.
Fuels such as sustainable aviation fuel have the advantage that few or no modifications are necessary on the aircraft itself, provided that the fuel characteristics meet specifications for lubricity and density as well as adequately swelling elastomer seals in current aircraft fuel systems. Sustainable aviation fuel and blends of fossil and sustainably-sourced alternative fuels yield lower emissions of particles and greenhouse gases (GHGs). They are, however, not being used heavily, because they still face political, technological, and economic barriers, such as currently being more expensive than conventionally produced aviation fuels by a wide margin.IATA 2014 Report on Alternative Fuels
Some development of technology for hydrogen-powered aircraft started after the millennium and gained track since about 2020, but as of 2022 was still far away from outright aircraft product development.
Hydrogen fuel cells do not produce or other emissions (besides water). However, hydrogen combustion does produce emissions. Cryogenic hydrogen can be used as a liquid at temperatures below 20K. Gaseous hydrogen involves pressurized tanks at 250–350 bar. With materials available in the 2020s, the mass of tanks strong enough to withstand this kind of high pressure will greatly outweigh the hydrogen fuel itself, largely negating the weight to energy advantage of hydrogen fuel over hydrocarbon fuels. Hydrogen has a severe volumetric disadvantage relative to hydrocarbon fuels, but future blended wing body aircraft designs might be able to accommodate this extra volume without greatly expanding the wetted area.
Even if finally practical, the industry timeline for adopting hydrogen is fairly lengthy. Alternatives to conventional aviation fuel available in the near term include aviation biofuel and synthetically created fuel (aka "e-jet"). These fuels are collectively referred to as "Sustainable Aviation Fuel" (SAF).
Jet fuel is a gas turbine fuel used in propeller and jet fixed-wing aircraft and helicopters. It has a low viscosity at low temperature, has limited ranges of density and calorific value, burns cleanly, and remains chemically stable when heated to high temperature.
Aviation gasoline, often referred to as avgas or 100-LL ( low-lead), is a highly refined form of gasoline for aircraft, with an emphasis on purity, engine knock characteristics and minimization of spark plug fouling. Avgas must meet performance guidelines for both the rich mixture condition required for take-off power settings and the leaner mixtures used during cruise to reduce fuel consumption. Aviation fuel can be used as CNG fuel.
Avgas is sold in much lower volume than jet fuel, but to many more individual aircraft operators, whereas jet fuel is sold in high volume to large aircraft operators, such as airlines and militaries.
Specific cases are:
Alcohol, alcohol mixtures, and other alternative fuels may be used experimentally, but alcohol is not permitted in any certified aviation fuel specification. In Brazil, the Embraer Ipanema EMB-202A is a version of the Ipanema agricultural aircraft with a modified Lycoming IO-540-K1J5 engine so as to be able to run on ethanol. Other aircraft engines that were modified to run on 100% ethanol were several other types of Lycoming engines (including the Lycoming 235N2C, and Lycoming IO-320) and certain Rotax engines. Rotax engines on ethanol/conventional fuel blend
A worry is that a local aviation fuel tax would cause increased tankering, where airlines carry extra fuel from low tax jurisdictions. This extra weight increases fuel burn, thus a local fuel tax could potentially increase overall fuel consumption. To avoid increased tankering, a worldwide aviation fuel tax has been proposed. Australia and the United States oppose a worldwide aviation fuel tax, but a number of other countries have expressed interest.
During a debate in the UK Parliament, the foregone tax income due to the exemption of tax on aviation fuel was estimated at £10 billion annually.
The planned inclusion of international aviation into the European Union Emission Trading Scheme in 2014 has been called an "illegal tax" by countries including the US and China, which cite the Chicago Convention.
Aviation fuel is transferred to an aircraft via one of two methods: overwing or underwing.
For pressure refueling, a high-pressure hose is attached and fuel is pumped in at 275 kilopascal (40 psi) and a maximum of 310 kPa (45 psi) for most commercial aircraft. Pressure for military aircraft, especially fighters, ranges up to 415 kPa (60 psi). Air being displaced in the tanks is usually vented overboard through a single vent on the aircraft. Because there is only one attachment point, fuel distribution between tanks is either automated or controlled from a control panel, either at the fueling point or in the cockpit. An early use of pressure refueling was on the de Havilland Comet and Sud Aviation Caravelle. Larger aircraft allow for two or more attachment points; however, this is still referred to as single-point refueling, as either attachment point can refuel all of the tanks. Multiple attachments allow for a faster flowrate.
Jet fuel is clear to straw-colored and is dispensed from a special nozzle, called a J spout or duckbill, that has a rectangular opening larger than 60 mm diagonally, so as not to fit into avgas ports. However, some jet and other turbine aircraft, such as some models of the Astar helicopter, have a fueling port too small for the J spout, and thus require a smaller nozzle.
Aviation fuel can cause severe environmental damage; all fueling vehicles must carry equipment to control fuel spills. Fire extinguishers must be present at any fueling operation. Airport firefighting forces are specially trained and equipped to handle aviation fuel fires and spills. Aviation fuel must be checked daily and before every flight for contaminants such as water or dirt.
Avgas is the only remaining lead-containing transportation fuel. Lead in avgas prevents damaging engine knock, or detonation, that can result in a sudden engine failure.
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