Aircraft Fuel System Components: All You Would Want to Know

Are you looking for aircraft fuel system components?

So, first, you must know about the aircraft fuel system.  The aircraft fuel system serves the purpose of loading, storing the fuel. In addition, the system also manages and delivers aviation fuel to the propulsion system and power unit of an aircraft.

Moreover, the working of an aircraft fuel system depends on the type of aircraft or aircraft’s performance. However, the basic working principle is that more air enters the tank when fuel burns. Thus, increasing the capacitance of the fuel system. This increase leads to the automatic calculation of fuel. And it eventually signals the pilots about the fuel status on the dashboard. Moreover, this system functions efficiently due to the presence of various aircraft fuel system components. Thus, this article will help to learn about the aircraft fuel system components in detail.

What Are The Aircraft Fuel System Components?

Different aircraft’s functions use various fuel systems depending on the size and type of aircraft. Thus, we will discuss aircraft fuel system components and know the importance of each of them.

Aircraft Fuel System Components

Gravity feed system

The gravity feed system is the most straightforward fuel system. This system does not use any fuel pumps to feed the engine. Most commonly, the high wing or low power aircraft uses this system. However, it works on earth’s gravity principle, where the gravitational forces help to transfer the fuel to the engine from the fuel tank. In this system, the designs are such that fuel tanks are above the engine or carburetor. And the lines feed the fuel into the propulsion system through gravity. In the high wing aircraft, fuel tanks are on both wings. In addition, there is a shut-off valve with a fuel ON or OFF position. Moreover, this valve connects to both the right and left fuel tanks. Finally, there is the selector valve that offers four functions:

  • Shut off the fuel to the engine.
  • Fuel feeding into the right-wing
  • fuel feeding into left-wing.
  • Fuel feeding into the engine from both wings.

Moreover, the design has a strainer draining the water and sediment before the fuel enters the carburetor. In addition, the Primer pump present in this feed system pumps the raw fuel that enables the engine to start. Finally, the vents present in both tanks help to maintain atmospheric pressure.

Fuel pump system

Aircraft with low and mid-wing or high power use a fuel pump system. These aircraft use one or more pumps for feeding fuel to the engine. Moreover, the fuel pump system consists of two pumps. These pumps are electric-driven, and the other is the engine-driven pump. In addition, this system uses a shut-off valve same as a gravity feed fuel system.  The selector valves connect both the tanks. But, it does not allow to feed the engine with both tanks simultaneously. However, it works like if fuels get over in one tank, then the pump would withdraw fuel from the other one.

Moreover, like the Gravity fuel system, it does not require vents, as there is no need to maintain pressure between both tanks. Thus, out of two pumps, engine-driven pumps work as primary pumps. At the same time, electric pumps are supporting pumps in times of primary pump failure. Moreover, an electric pump prevents vapor lock when a flight is at a high altitude.

Fuel tanks

The location and types of fuel tanks depend on the aircraft’s size, shape, and design. For example, low power or high wing aircraft has a fuel tank above the wing. In contrast, low-wing aircraft have fuel tanks below the wing. Moreover, there are three fuel tanks in the plane:

  • Removable tanks
  • Bladder tanks
  • Integral tanks

However, the ideal fuel tanks can store and deliver fuel at the appropriate pressure and flow efficiently. Thus, it is one of the vital aircraft fuel system components.

Fuel cells

Fuel cells are present within the fuel tank. There are two types of fuel cells.

  • Bladder fuel cell: These fuel cells are of rubber or nylon. So, they do not react with the fuel and are non-self-sealing. Moreover, the ideal fuel cells sit in the cavity perfectly and help to reduce the weight of the tank.
  • Integral Fuel cell: These are permanent and are on the wings of the plane. Moreover, it is also known as a wet wing due to its design. However, the integral fuel cell seals permanently, preventing any fluid from flowing without leaking.

Fuel primers

The primary function of the fuel primer is that it creates a mixture of air and fuel for combustion. This combustion method vents out the entrapped air and vaporizes fuel from carburetors. Thus, it keeps the engine running efficiently. Moreover, to avoid wastage of primer after use, lock the primer after use. Otherwise, it will leak out and cause fuel to mix with air.

Fuel lines

Aircraft uses fuel lines that may be rigid and flexible that join fuel tanks with various components. However, each fuel line has a color code for identification. Moreover, this aircraft fuel system component is essential as it delivers fuel from the tank to the engine. In addition, in intense heat areas, the fire-resistant hose is present. In a region where there is a chance of heat, abrasion, or debris, stainless steel fuel lines come into action.

Fuel gauges

The fuel gauge is the aircraft fuel system component that indicates the fuel tank’s amount of fuel. This indicator is on the same level as an engine made of glass or plastic tube.

Fuel valves

The aircraft uses fuel valves to shut off the fuel or to guide the route of fuel. Moreover, the plane consists of sump drain valves and a selector valve. Crew can manually operate the fuel valves and run through an electric motor.

Fuel selector

Fuel selector serves the function of controlling the direction of the fuel flow. Moreover, it acts as a fuel shut-off, or right and left shut off.

Fuel filters

Fuel filters are the aircraft’s fuel system components that remove the microparticles in the fuel. These components are present in fuel pumps. They are fine-mesh steel wires between the fuel pump and fuel control.

Fuel strainers

Fuel strainers are the plastic fabric that filters the fuel before entering it into the fuel line.

Fuel grades

Fuel grades in aircraft are of different types.  For example, the Avgas fuel grades are Avgas 100/130, Avgas 100LL, UL 91 and UL 94, and many more. However, never use Avgas which experts do not recommend for aircraft.

Fuel heaters

Fuel heater is among the essential aircraft fuel system components that warm up the fuel when fuel tanks cool below 32F. There are chances to form ice in the fuel filters, so heaters warm the fuel and improve combustion.

Understanding the Fuel Systems of an Aircraft: Gravity Feed System and Pressure Feed Fuel System

Final Words

Various aircraft fuel components are necessary for loading and delivering fuel to the propulsion system. However, discussing the aircraft fuel system components, they unite to provide two fuel systems. That is the gravity feed system and fuel pump system. So, concluding, we get those various components are essential for the functioning of the aircraft’s fuel system.


What are the types of aircraft fuel systems?

There are three fuel systems present in single or multi-engine aircraft.

  • Gravity feed fuel system – It delivers fuel based on gravity. The tank is above the engine, and fuel lines provide fuel to the engine via gravity.
  • Pump feed fuel system- It delivers fuel via electric and engine-driven pumps.
  • Fuel-injected aircraft fuel system- It delivers fuel by spraying method. Moreover, an electric pump delivers by spraying fuel directly into the carburetor cylinders.

Where is the fuel tank in an aircraft?

You may find a fuel tank in the wings or fuselage of the aircraft. Moreover, in some cases, fuel tanks are in Empangeni.  The fuel tanks in the wings enable the aircraft to reduce the complexity of the fuel system. In addition, locating fuel tanks outside of the aircraft ensures passenger safety.

Why is fuel stored in the wings of aircraft?

Storing fuel in the wings of aircraft has three significant reasons:

  • It balances the wings lift and fuselage weight. Thus, improving the structural efficiency of the plane. Moreover, it counteracts the down bending and up bending along the wings. Hence, reducing the wing root moments.
  • It manages the complexity of the fuel system as it becomes effortless to direct the fluid into the engine from wings.
  • Locating fuel in the wings ensures passenger and goods safety. This location keeps passengers safe from leakage, accidental fires, or other issues related to the fuel tank.

Which gas is used for purging an aircraft fuel tank?

Nitrogen gas displaces the oxygen present in the fuel tank of the aircraft. This aircraft fuel inserting system is known as nitrogen purging. Moreover, the purging of an aircraft fuel tank prevents formations of the atmosphere that supports fire and explosion. Thus, Nitrogen purging prevents any fire hazards inside the fuel tank.

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