FUEL SYSTEM

A320 FUEL 

There are seven fuel tanks; three in each wing and one in the fuselage.The main wing tanks are divided into two cells, inners and outers. Each wing also has a vent surge tank, that is located outboard of the outer wing tanks to compensate for expanding fuel. When the aircraft has been refueled to maximum capacity, the vent surge tanks allow for 2% expansion or a 20°C rise in fuel temperature. Fuel from the vent tanks drains into the outer cells when capacity is available. The tank in the fuselage is called the centre tank. Fuel cannot be transferred from tank to tank except on the ground during refueling operations.

FUEL PUMPS 

In normal operation, each engine is fed either one pump in the centre tank or two pumps from an inner wing tank. The wing tanks are fitted with sequence valves to ensure that when all pumps are running, the centre tank will supply fuel preferentially.

CROSSFEED VALVE 

The cross feed valve has two electric motors and can be used to balance the fuel load by feeding two engines from one tank or one engine from two tanks.

TRANSFER VALVES 

Two transfer valves are installed to transfer fuel from the outer tanks to the inner tanks. The transfer takes place when the inner tanks are depleted to 750 KGS. When open, the valves remain open until the next refueling, when they close. During steep descents or accelerations/decelerations, the valves may open before the 750 KG threshold.

SUCTION VALVES 

The suction valves are closed when there is normal fuel pressure from the boost pumps. The valves open to allow gravity feed from the wing tanks, in case of electrical failure. The centre tank pumps are not fitted with suction pumps, so gravity feed is not possible from the centre tank.

ENGINE LP VALVES 

The LP valves allow the fuel to be cut off form the engines; the valves can be closed by the engine master switches or ENG FIRE pbs.

APU FEED 

The APU has its own fuel pump, used for APU start when fuel pressure is low (due to a loss of AC power). The APU fuel supply is from the left side of the fuel manifold.

NORMAL FUEL FEED SEQUENCE 

All pumps are switched on prior to start up and the MODE SEL is checked to be in AUTO. After both engines are started, if there is fuel in centre tank, the pumps will run for a 2 minute test sequence, and then shutoff until the slats are retracted when airborne or re-selected down; this prevents take-off and landing using the centre tank. The centre tank pumps will then run until 5 minutes after the centre tank is empty. The wing tank pumps run continuously. An ECAM warning will be given during AUTO operation, if the centre tank has more than 250 KGS of fuel and either inner tank has less 5000 KGS.

IDG RECIRCULATION COOLING SYSTEM 

Fuel is directed through the IDG heat exchanger and then back through the fuel return valve to the outer tanks. The fuel return valve is controlled by the FADEC. If the outer tanks are already full, the recirculated fuel spills into the inner tanks though a spill pipe. If the inner tanks are already full, then the centre tank pumps are automatically turned off to allow fuel to burnt from the inner tanks. The inner tanks will supply the engines until approximately 500 KGS of fuel has been used, and then the centre tanks will resume operation.

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