An aircraft fuel system enables fuel to be loaded, stored, managed and delivered to the engines of an aircraft. Fuel systems differ greatly from aircraft to aircraft due to the relative size and complexity of the aircraft in which they are installed.
The fuel system is one of the more complex aspects of the gas turbine engine. It must be possible to increase or decrease the power so as to obtain the thrust required for any operating condition. In turbine-powered aircraft, this control is provided by varying the flow of fuel to the combustion chambers.
The quantity of fuel supplied must be adjusted automatically to correct for changes in ambient temperature or pressure. If the quantity of fuel becomes excessive in relation to mass airflow through the engine the limiting temperature of the turbine blades can be exceeded, or it will produce compressor stall and a condition referred to as rich blowout.
The fuel system must deliver fuel to the combustion chambers not only in the right quantity, but also in the right condition for satisfactory combustion. The fuel nozzles form part of the fuel system and atomize or vaporize the fuel so that it ignites and burns efficiently.
A320 Fuel System
Main Purpose Of Fuel System
- Stores fuel in tanks
- Supplies fuel to the engines and APU (Auxiliary Power Unit)
- Controls the transfer of fuel from the Centre tanks to the Wing tanks
- Circulates fuel to cool the IDG (Integrated Drive Generator)
- Keeps fuel in the outer tanks for wing bending and flutter relief
- The fuel is stored in the Wings, in the Centre tank, and in the additional Centre tank
- Wings have Inner tank & Outer tank
- A vent surge tank is present outboard of the outer tank of each wing
- If the A/C has been refuelled to it’s maximum capacity, fuel can expand by 2%
- (20 degree temperature rise) without spilling
Fuel Feed Sequence
The tanks empty in the following sequence :
- The ACT2: Fuel transfers into the Centre tank
- The ACT1: Fuel transfers into the Centre tank
- The Centre tank
- The Inner tanks: Each inner tank empties down to 750kg
- The Outer tanks: Fuel transfers into the inner tanks
NOTE: Additional Centre Tanks (ACTS) are not available in all the fleet, it depends upon the company requirement
- The system has 6 main fuel pumps or 4 fuel pumps (in case of jet pumps )
- The engines are supplied fuel directly from the inner tanks, the fuel is transferred from the other tanks to the inner tanks
- In normal operation, each engine is supplied from two pumps, in it’s own side inner tank
- All inner tank pumps remain operational throughout the flight, they are fitted with pressure relief sequence valves to ensure that, the centre tanks deliver fuel preferentially
- Transfer valves: Two electrical Transfer valves are fitted to transfer fuel from outer to inner tank
- Cross Feed valve: A Cross Feed valve controlled by double motor allows both engines to be fed from one side or engine to be fed from both sides
- Suction valves: Closed by pumps pressure in normal operation, they allow engines to be fed by gravity if the wing tank pumps fail
The control of fuel flow to the combustion chamber and fuel recirculation is done by a computer is known as FADEC- Full Authority Digital Engine Control system.
To know more about the working of the A320 Engines and the function of FADEC – you can read our blog in this segment.
Do let us know your reviews in the comment section below!