What is the primary function of the outflow valve in a pressurized cabin?

• A. Maintains cabin altitude
• B. Regulates engine temperature
• C. Filters air
• D. Increases cabin pressure during climb

Answer: (A)

The outflow valve’s job is to regulate cabin pressure by venting air to the outside. The cabin is pressurized by bleed air from the engines through the air conditioning packs, and the outflow valve controls how much of that air escapes. By opening more, it releases more air and allows cabin pressure to drop toward the desired setpoint; by closing, it traps more air to raise or maintain the pressure. This balancing act keeps the cabin altitude at a safe, comfortable level as the airplane climbs or descends. It does not regulate engine temperature or filter air, and it does not increase cabin pressure during climb—the pressurization supply determines pressure, while the valve simply vents to hold it steady.