Which component regulates the operation of the air conditioning packs on the A320?

• A. The APU control system.
• B. The bleed air temperature sensor.
• C. PACK selectors regulate the operation of the packs.
• D. The environmental control computer.

Answer: (C)

The packs are commanded directly by the PACK selectors. These switches determine how the air conditioning packs operate: ON runs the packs continuously, OFF disables them, and AUTO lets the Environmental Control System decide when to start and stop the packs to meet cabin temperature and demand. The APU control system is only involved in providing bleed air when needed, not in regulating pack operation. The bleed air temperature sensor provides data used by the system to regulate temperatures but does not itself turn packs on or off. The Environmental Control Computer coordinates automatic control, but the direct regulation input you use as the crew is the PACK selectors.