What are the maximum positive and negative cabin pressure differentials?

• A. Positive 8.7 PSI; Negative -0.5 PSI
• B. Positive 9.5 PSI; Negative -1.0 PSI
• C. Positive 7.5 PSI; Negative -0.3 PSI
• D. Positive 8.0 PSI; Negative -0.6 PSI

Answer: (A)

Cabin pressure differential is the difference between what’s inside the cabin and the air outside. The aircraft structure is designed as a pressure vessel, able to tolerate a certain positive differential (cabin higher than outside) and a small negative differential (cabin lower than outside) without failing or leaking badly.

For this airplane, the certified limits are a maximum positive differential of 8.7 psi and a maximum negative differential of −0.5 psi. These values come from the fuselage’s structural strength and safety margins established during certification, ensuring safe operation during all phases of flight and in pressure transient events. Therefore, the best answer reflects these published limits: the cabin can be pressurized up to 8.7 psi above outside air, and up to 0.5 psi below outside air. The other options propose limits beyond or inconsistent with the aircraft’s certified envelope.