If a cabin pressure controller fails, what happens?

• A. The system automatically switches to the second cabin pressure controller
• B. The system shuts down cabin pressurization
• C. Crew must manually select an alternate controller
• D. Cabin pressure is maintained by auto bleed valve only

Answer: (A)

Redundancy is built into the cabin pressurization system so it can keep working even if one controller fails. With two controllers, the system automatically switches to the standby controller and continues regulating cabin pressure by modulating the outflow/bleed as commanded. This failover happens without crew action, so pressurization is maintained and alarms may alert you only to the fault in the primary channel, not to a loss of pressurization.

Shutting down cabin pressurization isn’t the design goal; automatic switchover preserves operation. Requiring crew to manually select an alternate controller can be necessary only if automatic failover isn’t available, which isn’t the typical scenario here. Relying on the bleed valve alone wouldn’t keep proper cabin pressure without accurate controller commands to modulate it.