How many safety valves are in the tail cone, and what do they back up?

How many safety valves are in the tail cone, and what do they back up?

• A. One backs up positive pressure
• B. Two: one backs up positive pressure, the other backs up negative pressure
• C. Three: backups for both positive and negative pressure with separate protections
• D. Two: both backup positive pressure only

Answer: (B)

Redundancy in the pressurization system protects the cabin from both over- and under-pressurization. The tail cone houses two safety valves so there is a backup path for each direction of pressure change. One opens to relieve when cabin pressure would exceed the safe limit, preventing over-pressurization. The other opens when cabin pressure would drop too low (negative pressure), allowing relief or air ingress to protect the structure and occupants. If the primary relief or outflow path fails or is insufficient, these two valves provide separate protections for positive and negative pressure, ensuring safe cabin differential throughout flight.

Redundancy in the pressurization system protects the cabin from both over- and under-pressurization. The tail cone houses two safety valves so there is a backup path for each direction of pressure change. One opens to relieve when cabin pressure would exceed the safe limit, preventing over-pressurization. The other opens when cabin pressure would drop too low (negative pressure), allowing relief or air ingress to protect the structure and occupants. If the primary relief or outflow path fails or is insufficient, these two valves provide separate protections for positive and negative pressure, ensuring safe cabin differential throughout flight.