Note: Some aircraft modifications may affect the tanks capacity on A340-500/-600. Particularly, two RCT sizes are available on A340-500 (5 or 7 frame). The information presented in this brochure is applicable to 5-frame RCT. Please refer to Weight and Balance Manual or to the Aircraft Flight Manual for relevant information.
SYSTEMS

B. FUEL SYSTEMS

SYSTEMS

3.2. Fuel systems
All the aircraft of the long-range family basically follow the same guidelines in terms of fuel system. The main differences between the models mainly result from the number of engines and from the tanks that actually equip the aircraft.
In order to take advantage of the large amount of fuel on board and of the possible influence that this fuel position may have on the aircraft CG position, A330/A340 aircraft are fitted with a CG control system involving trim tank transfers that enables to keep the CG as aft as possible during the flight to optimize the fuel consumption.
3.2.1. Engine feed
A dedicated collector cell located in the inner wing tanks feeds each engine:
.  On A330, there is one collector cell per inner tank. Each cell includes two main fuel pumps. One standby pump is installed in the inner tank outside the collector cell.
.  On A340-200/-300, two collectors cells are located in each inner tank. On A340-500/-600, there is one collector cell in each of the four inner tanks. For all A340s, each collector cell consists in one main fuel pump and one standby fuel pump.
Each collector cell contains about 1000 kg and is maintained full in order to protect the engine feed. A cross feed valve is associated with each engine. When the cross feed valves are open, any pump is able to supply any engine.
3.2.2. Fuel transfers
This paragraph aims at briefly describing how the various fuel transfers are performed during the flight.
The collector cells located in the inner tanks ensure the engine feed. That implies that the fuel from the other tanks has to be transferred in the inner tanks: . Two pumps enable the transfer from center tank (when applicable). They run continuously as long as there is fuel in the center tank. . Fuel transfer from outer tanks is done by gravity and controlled by transfer valves.
For ACT (when fitted) and for RCT on A340-500, the fuel is transferred to the center tank by pressurization.
The CG control system generates trim tank transfers during the flight:
. Forward transfers: Some aircraft are equipped with one trim tank forward transfer pump for the fuel transfers from trim tank to the inner tanks or to the center tank. In case of the pump failure or if the aircraft is not fitted with it, these transfers are done by gravity. A340-500/-600 aircraft are basically fitted with two forward transfer pumps.
　
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