The Maximum relief differential pressure is which value?

The Maximum relief differential pressure is which value?

• A. 8.7 PSI
• B. 9.0 PSI
• C. 10.0 PSI
• D. 7.5 PSI

Answer: (A)

In a pressurized aircraft, the cabin is kept at a higher pressure than the outside air, and the airframe is designed to tolerate only a certain maximum difference between those pressures. A relief path is built into the system to prevent over-pressurizing the fuselage. The maximum relief differential pressure is the specific pressure difference at which that relief path opens to vent cabin air and keep the differential from climbing higher. For the CRJ-550, that value is 8.7 psi, meaning once the cabin pressure exceeds about 8.7 psi above ambient, the relief system begins venting to protect the airframe. If this were set lower, it would vent during normal operation; if higher, the fuselage could be stressed beyond its certified limit.

In a pressurized aircraft, the cabin is kept at a higher pressure than the outside air, and the airframe is designed to tolerate only a certain maximum difference between those pressures. A relief path is built into the system to prevent over-pressurizing the fuselage. The maximum relief differential pressure is the specific pressure difference at which that relief path opens to vent cabin air and keep the differential from climbing higher. For the CRJ-550, that value is 8.7 psi, meaning once the cabin pressure exceeds about 8.7 psi above ambient, the relief system begins venting to protect the airframe. If this were set lower, it would vent during normal operation; if higher, the fuselage could be stressed beyond its certified limit.