What is the maximum differential pressure allowed above 37,000 ft?

What is the maximum differential pressure allowed above 37,000 ft?

• A. 7.0 psi
• B. 7.8 psi
• C. 8.4 psi
• D. 8.8 psi

Answer: (C)

The key idea is that the fuselage can only tolerate a certain difference between the air pressure inside the cabin and the air pressure outside. That difference, called differential pressure, is set by the airplane’s structure and certification and the pressurization system works to stay within that ceiling. For the ERJ-175, the certified maximum differential pressure is 8.4 psi. This limit applies at cruise, including operations above 37,000 ft, to protect the fuselage from overstress. So 8.4 psi is the highest allowable difference you can maintain; attempting to go higher (like 8.8 psi) would exceed the structural limit. The smaller values are simply below the allowable maximum, not the ceiling you must hit.

The key idea is that the fuselage can only tolerate a certain difference between the air pressure inside the cabin and the air pressure outside. That difference, called differential pressure, is set by the airplane’s structure and certification and the pressurization system works to stay within that ceiling.

For the ERJ-175, the certified maximum differential pressure is 8.4 psi. This limit applies at cruise, including operations above 37,000 ft, to protect the fuselage from overstress. So 8.4 psi is the highest allowable difference you can maintain; attempting to go higher (like 8.8 psi) would exceed the structural limit. The smaller values are simply below the allowable maximum, not the ceiling you must hit.