What is the maximum differential overpressure?

What is the maximum differential overpressure?

• A. 7.5 psi
• B. 8.0 psi
• C. 8.8 psi
• D. 9.0 psi

Answer: (C)

The key idea is that there is a structural limit to how much pressure difference the airplane’s fuselage can safely handle between the inside and outside air. This differential pressure is what keeps the cabin pressurized at altitude, but pushing beyond the design limit risks damage. For the ERJ 175, that maximum differential is 8.8 psi. The pressurization system uses this limit to regulate cabin pressure and, if necessary, relieve excess pressure to stay within safe bounds. So, among the given options, 8.8 psi is the highest allowable differential, matching the aircraft’s published limit. Values below it are simply lower limits, not the maximum. A value like 9.0 psi would exceed the structural limit and could trigger relief or a fault.

The key idea is that there is a structural limit to how much pressure difference the airplane’s fuselage can safely handle between the inside and outside air. This differential pressure is what keeps the cabin pressurized at altitude, but pushing beyond the design limit risks damage. For the ERJ 175, that maximum differential is 8.8 psi. The pressurization system uses this limit to regulate cabin pressure and, if necessary, relieve excess pressure to stay within safe bounds.

So, among the given options, 8.8 psi is the highest allowable differential, matching the aircraft’s published limit. Values below it are simply lower limits, not the maximum. A value like 9.0 psi would exceed the structural limit and could trigger relief or a fault.