At approximately what cabin altitude does the outflow valve fully close?

• A. 12,000 feet
• B. 14,800 feet
• C. 15,000 feet
• D. 16,000 feet

Answer: (B)

The outflow valve is what the cabin pressure controller uses to regulate venting of air from the pressurized cabin to the ambient environment. As you climb, the controller reduces the amount of air vented to hold the cabin at the commanded altitude, so the valve moves toward less open and eventually to fully closed. In the PC‑12 NGX, that fully closed position occurs at about 14,800 feet cabin altitude. At this point the system isn’t venting air anymore to maintain pressure, and the remaining pressure is held by the established differential pressure limits and safety valves. So, the approximate cabin altitude where the outflow valve fully closes is 14,800 feet.