Air Conditioning Control Panel is part of A320 Overhead panel
Pack Flow Selector #
If the APU is supplying bleed air or one air conditioning pack fails, high flow is delivered regardless of pack flow selector’s position.
LO – If LOW flow is selected and the temperature demand cannot be satisfied, the pack reverts to normal flow.
HI – If HIGH flow is selected on the pack flow selector, the engine IP air is normally sufficient to supply the required air flow at normal thrust power settings. When IP air is not sufficient, the HP air valve will open to provide additional air pressure.
However, at idle power the actual air flow will be LO due to insufficient air pressure from both the IP and HP.
The pack flow selector allows for selecting the desired pack flow based on the passenger load:
- LO is normally selected if less than 115 passengers are expected
- NORM is selected if 115 passengers or more are expected
- HI is selected if abnormally hot and humid conditions exist.
Temperature Selectors #
Cockpit and Cabin Zone Temperature Selectors
The zone controller regulates the temperature of the cockpit and two cabin zones. The zone controller modulates the airflow through the trim air valves to optimize cockpit and cabin temperature regulation. The temperature is regulated between 64°F and 86°F. There is no manual means of regulating hot air pressure or trim air valves. The zone controller has a primary and redundant secondary channel for automatically regulating zone temperature optimization.
If the primary zone controller channel is operating normally and the secondary zone controller channel fails, then temperature control remains normal
If the primary zone controller channel failsthe secondary zone controller channel takes over, then the hot air pressure regulating valve and trim air valves close, and the flow control and temperature optimization are lost. The cockpit temperature is controlled to 76°F by pack 1. The forward and aft cabins are controlled to 76°F by pack 2.
If both zone controller channels fail, then the packs produce a fixed temperature of 68°F from pack 1 and 50°F from pack 2. In this situation a message PACK REG appears on the Engine Warning Display and all information is removed from the ECAM COND page.
Hot Air Switch #
ON – When all lights on the Hot Air switch are extinguished indicates the switch is ON. Cycling the switch to ON allows the hot air pressure regulating valve to supply hot air to the trim air valves.
OFF – When the OFF light illuminates white the hot air pressure regulating valve and trim air valves are closed and resets the fault circuit.
HOT AIR VALVE FAILS CLOSED – The hot air pressure regulating valve controls the supply of hot air to the trim air valves. If the hot air pressure regulating valve fails closed, trim air is not available. In this case the cockpit temperature selector controls the output temperature from pack 1. The mean value of the forward and aft cabin temperature selectors control the output temperature of pack 2.
HOT AIR VALVLE FAILS OPEN – If the hot air pressure regulating valve fails open, the trim air system is not affected.
FAULT – An amber FAULT light indicates a duct overheat is detected. The hot air pressure regulating valve and trim air valves automatically close. The fault light remains illuminated until a lower temperature is sensed with the switch off.
The hot air pressure pressure regulating valve closes automatically if:
- The duct overheats or
- The cockpit trim air valve fails or
- Both trim air valves fail
Pack Switch #
ON is indicated when all lights are extinguished on the switch. Selecting the switch to ON allows the pack flow control valve to be regulated automatically by its respective pack controller.
FAULT – When the FAULT light illuminates amber, a compressor/pack overheat is detected or the pack flow control valve position disagrees with the selected position. The fault light remains illuminated until until the fault condition is corrected.
OFF – When the OFF light illuminates white, the pack flow control valve is closed.
Automatic Closure of Pack Flow Control Valve occurs when any of the following occurs:
- Upstream pressure is below minimum
- For a compressor outlet overheat
- During engine start sequence on the ground
- Corresponding fire switch is depressed
- If ditching switch is selected ON
Pack Controllers – The two packs operate automatically and independently of each other. Each pack is regulated by it’s respective dual channel pack controller. The pack controller receives demand signals from the zone controller to regulate the applicable pack temperature.
If the primary pack controller channel fails, the secondary pack controller channel automatically takes over and defaults to a fixed pack flow control pre-failure setting.
If the secondary pack controller channel fails, with the primary pack controller channel operating, pack regulation is not affected; however, related ECAM pack information is not displayed.
Should both pack controller channels fail, pack outlet temperature is controlled to a set temperature range by the pack anti-ice valve, and related ECAM pack information is not displayed.
Engine Bleed Switch #
FAULT – The engine bleed switch is normally selected to ON for flight conditions, commanding the engine bleed switch to open. The engine bleed fault light illuminates amber when the switch’s command position disagrees with the engine bleed valve position.
The engine bleed valve will close automatically if:
- The ENG BLEED switch is off,
- ENG FIRE switch pushed, or
- The BMC detects a fault or
- A pressure regulating and shut-off valve will close the engine bleed valve pneumatically if upstream pressure is low or reverse airflow occurs.
ON – Is indicated when all lights are extinguished on the engine bleed switch. Selecting the switch to ON commands the engine bleed valve to open.
OFF – When the OFF light illuminates white, the IP and HP valves are closed.
| NOTE With the ENG BLEED switch OFF, the FAULT light will extinguish when the ENG BLEED switch is selected OFF and the cause of the fault no longer exists. |
The BMC (Bleed Management Computer) closes the engine bleed valve electrically for any of the following fault conditions:
- Over-pressure downstream of bleed valve
- Bleed over-heat
- Wing or engine leak on associated side
- Bleed valve not closed during engine start, and/or bleed valve not closed with APU bleed valve open
Ram Air Switch #
OFF – Selecting the guarded ram air switch to OFF (no annunciation) closes the ram air inlet. The normal selected position.
In the event of a dual pack failure or for smoke removal, ventilation can be obtained by the ram air inlet.
ON – The ram air switch ON light illuminates white when selected ON. The ram air inlet opens if differential pressure is less than 1 PSI, if the DITCHING switch is in its normal guarded position and the cabin pressurization MODE SEL switch is selected to AUTO. If the differential pressure is greater than 1 PSI, then the ram air inlet remains closed.
APU Bleed Switch #
ON – Selecting APU BLEED switch to ON opens the APU bleed valve provided the APU N is greater than 95% and there is no leak on the APU or left bleed side. The ON light illuminates blue when the APU bleed valve is open. When the ON light extinguishes the APU bleed valve is closed.
FAULT – The APU bleed switch FAULT light illuminates amber when an APU leak is detected.
Cross Bleed Selector #
AUTO – When the Cross Bleed Selector is selected to AUTO, the cross bleed valve opens if the APU bleed valve is open; it closes the cross bleed valve if the APU bleed valve is closed or any air leak is detected (except engine start).
OPEN – When the Cross Bleed Selector is selected to OPEN, it opens the cross bleed valve.
SHUT – When the Cross Bleed Selector is selected to SHUT, it closes the cross bleed valve.
Leak Detection System #
The leak detection system senses overheat conditions in the vicinity of the hot air ducts located in the fuselage, pylons, and wings.
When a leak signal is activated:
- The BMC closes the engine bleed valve on the related side
- The ENG BLEED switch FAULT light illuminates
- The ECAM AIR L(R) WING or ENG 1(2) BLEED LEAK page is displayed
- The cross-bleed valve closes, if open, the APU bleed valve closes (except during engine start) if the leak involves the left wing.
