The ram air duct includes a check valve to provide ventilation when conditioned air is unavailable.

The ram air duct includes a check valve to provide ventilation when conditioned air is unavailable.

• A. True
• B. False
• C. Only during emergencies
• D. Not specified

Answer: (A)

In the environmental control system, ram air can be used to ventilate the cabin when conditioned air isn’t available. A one-way check valve in the ram air duct ensures this outside-air ventilation can flow into the cabin when needed, while preventing conditioned or cabin air from flowing back into the ram air path. When the packs are supplying conditioned air, the valve stays closed to avoid crossflow and to keep airflow properly directed; when ventilation from ram air is required, it opens to admit outside air. This is why the statement is true: the ram air duct is equipped with a check valve to provide ventilation when conditioned air is unavailable.

In the environmental control system, ram air can be used to ventilate the cabin when conditioned air isn’t available. A one-way check valve in the ram air duct ensures this outside-air ventilation can flow into the cabin when needed, while preventing conditioned or cabin air from flowing back into the ram air path. When the packs are supplying conditioned air, the valve stays closed to avoid crossflow and to keep airflow properly directed; when ventilation from ram air is required, it opens to admit outside air. This is why the statement is true: the ram air duct is equipped with a check valve to provide ventilation when conditioned air is unavailable.