An aircraft fuel system allows the crew to

pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...

, manage, and deliver

aviation fuel Aviation fuels are petroleum-based fuels, 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 enhan ...

to the

propulsion system Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...

and

auxiliary power unit An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115& ...

(APU) of an aircraft. Fuel systems differ greatly due to different performance of the aircraft in which they are installed. A single-engine piston aircraft has a simple fuel system; a tanker (such as the

KC-135 The Boeing KC-135 Stratotanker is an American military aerial refueling aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It is the predominant variant of the C-135 Stratolifter family of transport ...

), in addition to managing its own fuel, can also provide fuel to other aircraft.Taylor 1990, p. 164. Fuel is piped through fuel lines to a fuel

control valve A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressu ...

(usually known as the fuel selector). This valve serves several functions. The first function is to act as a fuel shut-off valve. This is required to provide the crew with a means to prevent fuel reaching the engine in case of an engine fire. The second function is to allow the pilot to choose which

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful ...

feeds the engine. Many aircraft have the left tank and right tank selections available to the pilot. Some

Cessna Cessna () is an American brand of general aviation aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of the Cessna Aircraft Company, an American general aviation aircraft manufacturing ...

airplanes feed only from both tanks; and many have the option to feed from left, right, or both tanks. The reason to have left only and right only options is to allow pilots to balance fuel load to reduce the banking moment. In some aircraft, the shut-off function is a different valve located after the fuel selector valve. Typically, after the selector valve—situated at a low point in the fuel run—there is a

gascolator A gascolator, also known as a ''main line strainer'', ''sediment bowl'' or ''fuel strainer'', acts primarily as a fuel drain for water and small particles of sediment and is usually found at the lowest point of an aircraft's fuel system. The gasco ...

— a fuel filter that can be opened on the ground and drained of fuel impurities denser than petroleum, mainly water and sediment. Other drainage points are in each tank (often more than one contaminant collection sump per tank) and at the injection pump. Each tank is vented (or pressurised) to allow air into the tank to take the place of burned fuel; otherwise, the tank would be in negative pressure which would result in engine

fuel starvation In an internal combustion engine, fuel starvation is the failure of the fuel system to supply sufficient fuel to allow the engine to run properly, for example due to blockage, vapor lock, contamination by water, malfunction of the fuel pump or in ...

. A vent also allows for changes in

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

and temperature.

Single-engine aircraft gasoline fuel system

The fuel level indication system in the simplest form in aircraft is a transparent window on the tank side and in its usual application a float-driven

potentiometer A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. The measuring instrum ...

installed in the tank. After the

TWA Flight 800 Trans World Airlines Flight 800 (TWA800) was a Boeing 747-100 that exploded and crashed into the Atlantic Ocean near East Moriches, New York, on July 17, 1996, at about 8:31pm. EDT, 12 minutes after takeoff from John F. Kennedy Internationa ...

disaster, a revision was made to aircraft fuel systems to address the potential explosion hazard of electrical components located in the fuel tank. Single-engine piston aircraft fuel level systems moved to utilize float level gauges from the CNG and LPG industries which had the float drive a

magnetic coupling A magnetic coupling is a coupling that transfers torque from one shaft to another, but using a magnetic field rather than a physical mechanical connection. Magnetic shaft couplings are most often used for liquid pumps and propeller systems, since ...

and relocated the potentiometer outside the fuel tank. Some single-engine aircraft use capacitive probes in the fuel tanks. As fuel is burned, more air enters the tank and the

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

increases; this is read by a computer and the fuel amount is calculated and displayed to the pilots. Magneto Resistive Level Sensor

Recent advances in

magnetoresistive Magnetoresistance is the tendency of a material (often Ferromagnetism, ferromagnetic) to change the value of its electrical resistance in an externally-applied magnetic field. There are a variety of effects that can be called magnetoresistance. So ...

technology have evolved new fuel level sensors for general aviation applications. This system is not affected by any additive or fuel combination to replace

100LL Avgas (aviation gasoline, also known as aviation spirit in the UK) is an aviation fuel used in aircraft with spark-ignited internal combustion engines. ''Avgas'' is distinguished from conventional gasoline (petrol) used in motor vehicles, ...

for piston-powered aircraft. Single-engine light aircraft fuel tanks are usually in the wings, but some aircraft have a small "header tank" between the normal fuel tank and the engine, to facilitate reliable fuel flow to the engine. On many small or very old single-engine header tanks (and even main tanks) are often mounted above and/or immediately behind the engine. A few (particularly

ultralight aircraft Ultralight aviation (called microlight aviation in some countries) is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and Aircraft flight control system, conventional three-a ...

) have them in the fuselage or on the airframe behind the pilot and/or passenger(s).VanWest, Jeff
"Legacy LSAs Choices: Champ Still a Winner: ...$20,000 airplanes worth buying,"
July 12, 2012 Updated: October 29, 2019, ''

Aviation Consumer Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot ai ...

'' "Super Cub PA-18: 150 HP: For 1974 and later,"
ca.1974, Piper Aircraft Corporation, scanned copy at Supercub.org, retrieved September 22, 2022"Budget Buys: Amicable Aeronca Chief,"
January 5, 2005, ''

AOPA Pilot The Aircraft Owners and Pilots Association (AOPA) is a Frederick, Maryland-based American non-profit political organization that advocates for general aviation. AOPA's membership consists mainly of general aviation pilots in the United States ...

,''

Aircraft Owners and Pilots Association The Aircraft Owners and Pilots Association (AOPA) is a Frederick, Maryland-based American non-profit political organization that advocates for general aviation. AOPA's membership consists mainly of general aviation pilots in the United States ...

, retrieved September 23, 2022Barnes, Sparky
"A Delightful Aeronca Anomaly: The stick-controlled Chief,"
May/June 2016, ''Vintage Airplane'' magazine,

Experimental Aircraft Association The Experimental Aircraft Association (EAA) is an international organization of aviation enthusiasts based in Oshkosh, Wisconsin, United States. Since its inception, it has grown internationally with over 200,000 members and nearly 1,000 chapt ...

, retrieved September 23, 2022"Flight Review: CGS Hawk Arrow,"
December 2010 ''Kitplanes,'' retrieved September 23, 2022

Multi-engine aircraft fuel system

Adding tanks and engines increases the complexity of the fuel system and its management. Additional features found in multi-engine aircraft are: *Each wing tank often has its own electric boost

fuel pump A fuel pump is a component in motor vehicles that transfers liquid from the fuel tank to the carburetor or fuel injector of the internal combustion engine. Carbureted engines often use low pressure mechanical pumps that are mounted outside the f ...

, and each engine has its own mechanical pump, replicating the fuel system described above for the single engine. *In case of single-engine operation, there is often a method incorporated to "cross-feed" the engine (left tank feeding right engine, or vice versa). *To balance asymmetric weight, flow valves and pumps often are used to feed both engines from one tank or simply to transfer fuel between tanks.

Turbine fuel system

All of the considerations made for the twin piston are applicable to turbine fuel systems. Additional consideration apply because of the higher altitudes, different fuel, lower temperatures, and longer flights. To avoid water condensation or the fuel itself solidifying at low temperatures (-55 °C), fuel tanks have thermometers and heating systems. Many are pressurized with engine

bleed air Bleed air is compressed air taken from the compressor stage of a gas turbine upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPCs) valves bleed air from high or low stage engine compressor sections. Lo ...

to keep moist air out and ensure positive pressure feed to the pumps. In larger aircraft, fuel tanks also are in the fuselage and their load affects the

center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force ma ...

of the aircraft. This imposes limitations on the amount of fuel carried and the order in which fuel must be used. Turbine engines burn fuel faster than reciprocating engines do. Because fuel needs to be injected in to a

combustor A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion chamber is f ...

, the injection system of a turbine aircraft must provide fuel at higher pressure and flow compared to that for a piston engine aircraft. The refueling system of larger aircraft includes a single positive pressure refueling point from which all tanks can be fueled. How much and to which tanks fuel is fed during refueling operations is determined by the controls in the refueling panel, usually installed nearby and accessible to ground crews.

External tanks

External tanks are used to extend the range of an aircraft.

Drop tank In aviation, a drop tank (external tank, wing tank or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often capable of being jettisoned. External tanks are commonplace on modern ...

s are used by combat aircraft that need to discard them after use for performance reasons. To transfer fuel from the tip tank to the main tank on each side, there must be a fuel pump in the tip tank.

References

Notes

Bibliography

* Taylor, John W.R. ''The Lore of Flight'', London: Universal Books Ltd., 1990. . {{Aircraft gas turbine engine components Aircraft fuel system components Aviation fuels Fuel system de:Kraftstoffsystem (Flugzeug)