Systems Guide

Aerosoft
Airbus A320/A321
SYSTEMS
Systems guide
Vol
4
04-03-8
28 October 2014
VENTILATION
The ventilation of avionics is controlled by the Avionics Equipment Ventilation Controller (AEVC). It provides
cooling of the avionics compartments using two fans, a heat exchanger that uses the outside skin of the aircraft to
cool the air and an inlet and outlet valve. Only the automated mode is simulated and you can see the ventilation
valve position on the CAB PRESS ECAM page. Battery, galley and toilet ventilation is provided by fans that draws
air from the cabin and vents it overboard via a vent in the aircraft skin.
Do note that the AEVC is very loud and other sounds from the aircraft systems that are heard on other aircraft
types are not heard on the Airbus A320 series.
APU
GENERAL
The Auxiliary Power Unit provides:
 Bleed air for engine starting
 Bleed air for air conditioning
 Electrical power for all the buses
The APU can be used on the ground and in flight with the following limitations:
 100% generator load up to 25,000 feet
 Full pneumatic and hydraulic pressure up to 20,000 feet
 Can be started using the battery up to 25,000 feet.
SYSTEM COMPONENTS
The APU consists of a gas turbine engine with an APU computer that manages the system. The air intake uses a
electrically operated inlet flap and the exhaust vents in the tail cone. The electrical starter will start the engine
when the inlet flap is fully opened. The fuel is taken from the left wing tank using a separate fuel pump.
AIR BLEED SYSTEM
Bleed air from the APU is selectable from the overhead panel and has priority over main engine bleed air as long
as the APU BLEED pb is ON. The bleed air can start engines and provide the air condition system.
CONTROLS AND DISPLAYS
The APU ECAM page displays the parameters of the APU. For the gas turbine engine N (in %) and EGT (in °C) are
available. The APU generator shows load (in %), voltage (in V) and frequency (in HZ) plus the connection to the
bus (arrow when connected, nothing when not connected). Bleed air shows pressure (in PSI) plus the position of
the valve (open or closed). All system messages are shown in green while within correct parameters, or amber
when outside correct parameters.
The APU MASTER SW pb on the overhead APU panel is pressed (ON will show) to power up the APU computer,
the fuel pump is activated and the air inlet is opened. When ON is shown the APU is ready to start.
The APU START pb starts the APU. When pressed it will show ON and the APU computer will command and
control the startup. Aircraft batteries must be selected ON, even when the engine generators are online. When