An aircraft fuel system allows the crew to

pump A pump is a device that moves fluids (liquids or gases), or sometimes Slurry, slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy. Mechanical pumps serve in a wide range of application ...

, manage, and deliver

aviation fuel Aviation fuels are either petroleum-based or blends of petroleum and synthetic fuels, used to power aircraft. They have more stringent requirements than fuels used for ground applications, such as heating and road transport, and they contain add ...

to the propulsion system and auxiliary power unit (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, while a tanker (such as the

KC-135 The Boeing KC-135 Stratotanker is an American military aerial refueling tanker aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It has a narrower fuselage and is shorter than the 707. Boeing gave ...

) not only manages its own fuel but can also provide fuel to other aircraft.Taylor 1990, p. 164. Fuel is piped through fuel lines to a fuel control valve (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 battlefield mobility provided by tracks and a powerful engine; ...

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 manufactu ...

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 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. A vent also allows for changes in

atmospheric pressure Atmospheric pressure, also known as air pressure or 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 1,013. ...

and temperature.

Single-engine aircraft gasoline fuel system

The fuel level indication system in the simplest form is a transparent window on the tank side and in its usual application a float-driven potentiometer installed in the tank. After the TWA Flight 800 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 component which transfers torque from one shaft to another using a magnetic field, rather than a physical mechanical connection. They are also known as magnetic drive couplings, magnetic shaft couplings, or magnetic disc co ...

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 ability of an object 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 two closely related ...

decreases; 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 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 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'' "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,'' Aircraft Owners and Pilots Association, 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. Since its inception, it has grown internationally with over 300,000 members and nearly 1,000 chapters worldwide. ...

, 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, 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 in aerospace engineering 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 (ASCPC) valves bleed air from low or high stage engine ...

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 barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For ...

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, burner can, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion ...

, 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 tanks are used by combat aircraft that need to discard them after use for performance reasons. A fuel pump is required to transfer fuel from a tip tank to a main 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)