What is the primary function of negative pressure relief valves?

• A. Control cabin altitude
• B. Protect the fuselage structure from negative pressure
• C. Regulate temperature in the cabin
• D. Release excessive cabin pressure

Answer: (B)

The primary function of negative pressure relief valves is to protect the fuselage structure from negative pressure. When the aircraft experiences rapid altitude changes or low-pressure situations, a negative pressure differential can occur inside the cabin. This can potentially lead to structural damage. The negative pressure relief valve helps to equalize pressure by allowing outside air to enter the cabin when this negative pressure occurs, ensuring the structural integrity of the aircraft is maintained.

Understanding that the function of this valve is specifically focused on pressure differences helps clarify its role within the aircraft systems. It directly addresses concerns related to the physical well-being of the aircraft's design under various flight conditions, which is vital for safety and performance.