When does the ground valve open or close?

When does the ground valve open or close?

• A. The ground valve closes when the main cabin door is closed prior to departure, and opens after landing with weight on wheels.
• B. The ground valve opens during start.
• C. The ground valve remains open at all times.
• D. The ground valve opens only during climb.

Answer: (A)

The ground valve is part of the environmental control/pressurization system and its position depends on whether the aircraft is on the ground and the door status. When preparing for departure with the main cabin door closed, the valve is kept closed so the cabin remains sealed and the ECS controls air flow without any outside-air path intruding during the preflight and boarding phase. After landing, once weight on wheels is detected, the valve opens to allow proper venting and air exchange with the outside environment as the airplane transitions to ground operations. This arrangement prevents unwanted air flow during flight preparation and then enables normal ventilation when the aircraft is on the ground.

The ground valve is part of the environmental control/pressurization system and its position depends on whether the aircraft is on the ground and the door status. When preparing for departure with the main cabin door closed, the valve is kept closed so the cabin remains sealed and the ECS controls air flow without any outside-air path intruding during the preflight and boarding phase. After landing, once weight on wheels is detected, the valve opens to allow proper venting and air exchange with the outside environment as the airplane transitions to ground operations. This arrangement prevents unwanted air flow during flight preparation and then enables normal ventilation when the aircraft is on the ground.