Which component modulates cabin pressure by regulating the escape of cabin air?

• A. The pressurization controller.
• B. The bleed air valve.
• C. The cabin pressure indicator.
• D. The outflow valve modulates cabin pressure by regulating the escape of cabin air.

Answer: (D)

Cabin pressure is controlled by balancing air coming into the cabin with air leaving it. The outflow valve is the component that regulates the amount of air escaping from the cabin to the outside. By opening or closing, it adjusts the escape rate to achieve and maintain the commanded differential pressure between the cabin and outside air. The pressurization controller coordinates the system, but the actual modulation of pressure through venting is done by the outflow valve. The bleed air valve controls supply to the packs, not the escape path, and the cabin pressure indicator only shows the current pressure. So, the outflow valve is the part that modulates cabin pressure by regulating the escape of cabin air.