The main purpose of outflow valves is to regulate cabin pressure automatically.

• A. Regulate cabin pressure automatically
• B. Regulate cabin temperature
• C. Control fuel flow
• D. Provide fresh air to cabin

Answer: (A)

Outflow valves regulate cabin pressure by controlling how much air leaves the cabin. They are part of the pressurization system and are driven automatically by the cabin pressure controller to maintain the set cabin pressure as the aircraft climbs or descends. By adjusting the valve opening, more air leaving lowers the cabin pressure, while less venting raises it, keeping the pressure differential within safe limits. This function is distinct from temperature control, which is done by the environmental control system packs and air mixing, and from providing fresh air or fuel flow, which are unrelated to the outflow valve.