What is the purpose of ram air valve in the air conditioning and pressurisation system?

• A. To vent cabin air to atmosphere during flight
• B. To provide cabin air in case of loss of pressurisation
• C. To regulate cabin temperature
• D. To vent excess humidity

Answer: (B)

The ram air valve’s purpose in the environmental control system is to provide cabin air in case of loss of pressurization. When the pressurization system can no longer maintain cabin pressure, the valve automatically opens to admit ambient outside air into the cabin ventilation path, helping to supply breathable air until normal systems are restored. This is distinct from venting cabin air to atmosphere (outflow valve), and it isn’t a direct regulator of temperature or humidity—those are handled by the packs and heat exchangers.