How is cabin pressure controlled at altitude?

How is cabin pressure controlled at altitude?

• A. The pilot manually controls the cabin altitude via a dial.
• B. Cabin pressure is maintained by ballast only with no automatic control.
• C. Outflow valve is controlled manually.
• D. The pressure controller automatically monitors cabin pressure and controls the outflow valve to maintain the desired cabin altitude.

Answer: (D)

Maintaining cabin pressure at altitude is done with an automatic feedback loop. The crew selects a desired cabin altitude, and sensors monitor the actual cabin pressure. The pressure controller compares the sensed pressure to the setpoint and automatically commands the outflow valve to open or close. If cabin pressure is too high, the valve opens more to vent air; if too low, the valve closes to retain air. This automatic regulation keeps the cabin at the chosen altitude while also managing the rate of pressurization and protecting against overpressure with relief valves as a safety backup.

Maintaining cabin pressure at altitude is done with an automatic feedback loop. The crew selects a desired cabin altitude, and sensors monitor the actual cabin pressure. The pressure controller compares the sensed pressure to the setpoint and automatically commands the outflow valve to open or close. If cabin pressure is too high, the valve opens more to vent air; if too low, the valve closes to retain air. This automatic regulation keeps the cabin at the chosen altitude while also managing the rate of pressurization and protecting against overpressure with relief valves as a safety backup.