On takeoff the outflow valve will close and pressurize the cabin to approximately how many feet below the field elevation?

On takeoff the outflow valve will close and pressurize the cabin to approximately how many feet below the field elevation?

• A. 50 feet
• B. 100 feet
• C. 150 feet
• D. 200 feet

Answer: (C)

When the outflow valve closes at takeoff, the cabin is sealed from venting air, allowing the bleed-air supply to build the cabin pressure quickly. The system is designed so that the cabin is pressurized to about 150 feet below the field elevation. In other words, the cabin altitude is set to be just a little lower than the airport’s altitude, which keeps the pressure differential within safe limits as the airplane begins its climb. After liftoff, the environmental control system continues to adjust the valve to maintain the target cabin altitude as outside pressure changes. This initial 150-foot差 helps ensure a comfortable, controlled pressurization without overshooting allowable limits.

When the outflow valve closes at takeoff, the cabin is sealed from venting air, allowing the bleed-air supply to build the cabin pressure quickly. The system is designed so that the cabin is pressurized to about 150 feet below the field elevation. In other words, the cabin altitude is set to be just a little lower than the airport’s altitude, which keeps the pressure differential within safe limits as the airplane begins its climb. After liftoff, the environmental control system continues to adjust the valve to maintain the target cabin altitude as outside pressure changes. This initial 150-foot差 helps ensure a comfortable, controlled pressurization without overshooting allowable limits.