How many outflow valves are there on the aircraft?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (A)

The cabin pressurization system relies on a controlled vent to regulate cabin pressure, letting air escape from the cabin to the outside. On this aircraft there is a single outflow valve that the pressure controller opens and closes to maintain the desired cabin altitude and differential pressure. A single valve keeps the system simple and reliable, while protection against overpressure is provided by separate relief mechanisms rather than multiple outflow valves. So, one outflow valve is the design used here.