What is the function of the cabin outflow valve?

What is the function of the cabin outflow valve?

• A. It heats cabin air as needed
• B. It filters cabin air for contaminants
• C. It regulates the rate at which cabin air exits, controlling cabin pressure
• D. It controls cabin humidity

Answer: (C)

The essential function is to regulate how fast cabin air leaves the cabin, which sets the cabin pressure. The cabin outflow valve vents conditioned air to the ambient environment, and its opening is adjusted automatically by the environmental control system to maintain the commanded cabin pressure (and corresponding cabin altitude). When cabin pressure is higher than the target, the valve opens more to let more air escape; when pressure is lower, it closes to retain air. This balancing act is what keeps the cabin at a safe, comfortable pressure during flight. The other tasks—heating the air, filtering contaminants, and controlling humidity—are handled by other parts of the environmental control system, not by the outflow valve.

The essential function is to regulate how fast cabin air leaves the cabin, which sets the cabin pressure. The cabin outflow valve vents conditioned air to the ambient environment, and its opening is adjusted automatically by the environmental control system to maintain the commanded cabin pressure (and corresponding cabin altitude). When cabin pressure is higher than the target, the valve opens more to let more air escape; when pressure is lower, it closes to retain air. This balancing act is what keeps the cabin at a safe, comfortable pressure during flight. The other tasks—heating the air, filtering contaminants, and controlling humidity—are handled by other parts of the environmental control system, not by the outflow valve.