Fuel pumps.

fuelpumps panel

There is one center tank and a left and right main tank. All tanks are an integral part of the wing. Each main tank is vented to a vent box in he opposite wingtip.

Each fuel tank has two AC boost pumps installed. A DC powered start pump is installed in he right main tank to provide fuel pressure for start of the APU or an engine if AC power is not available. This switch is placed on Engine starter panel.

During normal operation, he left main tank supplies the left engine and the right main tank supplies the right engine. The center tank fuel is transferred into left and right main tanks.

Later aircraft are equipped with an alternate Fuel Burn system. In these aircraft the center tank pump switches have three positions. The system is designed to reduce the risk of cold fuel reaching the upper part of the wing after landing. Thus reducing the risk of clear ice forming on the upper surface of the wing.
Left and right main tank BOOST PUMP SWITCHES.
Each main tank contains two fuel boost pumps designated as AFT and FWD. When a switch is placed in ON position, the corresponding boost pump is activated. The boost pumps operates in parallel.
The two center tank boost pumps operate in series. When placed in ON the center tank fuel will be used before the fuel in the main tanks due to the higher pump pressure.
With the switches in AUTO fuel from the center tank will be fed to the engines until the fuel level in the center tank reaches 5000-4100 kg. At this level the pumps are automatically turned off permitting the main tank pumps to feed the engines. When the level in the main tanks reach 2200-1700 kg, the center tank pumps will start again.