Pressurization control system has how many modes and what are they?

• A. Two: automatic and manual
• B. Four: automatic, semi automatic, manual, emergency
• C. Three: automatic controller, semi automatic, manual
• D. One: automatic

Answer: (C)

The system is designed to manage cabin pressure with three levels of automation, giving the crew options to let automation handle it or to intervene as needed.

• Automatic controller: The pressurization system automatically maintains the selected cabin pressure without crew input. It uses sensors and an outflow valve to hold the cabin altitude and differential pressure at the programmed values, adjusting continuously as flight conditions change.

• Semi automatic: Automation handles much of the task, but the crew must provide or confirm certain inputs, such as the target cabin altitude. This mode offers a balance between automation and pilot control, useful when some automation is available but not fully autonomous.

• Manual: The crew directly controls the cabin pressure, typically by adjusting the outflow valve or selecting manual mode. This is used when automation is unavailable or in abnormal/emergency situations.

Other options suggesting four modes or only one or two modes don’t align with how standard SMA pressurization systems are described, so the three-mode set—automatic controller, semi automatic, and manual—is the correct concept.