At what altitude does the differential pressure specification change from 7.8 psi to 8.4 psi?

At what altitude does the differential pressure specification change from 7.8 psi to 8.4 psi?

• A. 30,000 ft
• B. 37,000 ft
• C. 33,500 ft
• D. 40,000 ft

Answer: (B)

Delta P is the difference between the cabin pressure and the outside air pressure. The ERJ 175’s airframe is certified with two delta-P limits that depend on altitude: up to 37,000 ft the maximum differential is 7.8 psi, and above 37,000 ft it rises to 8.4 psi. So the altitude where the specification changes is 37,000 ft. This two-tier limit comes from how the aircraft is certified to handle pressurization loads across the flight envelope, balancing structural safety with the capabilities of the pressurization system at different cruise altitudes.

Delta P is the difference between the cabin pressure and the outside air pressure. The ERJ 175’s airframe is certified with two delta-P limits that depend on altitude: up to 37,000 ft the maximum differential is 7.8 psi, and above 37,000 ft it rises to 8.4 psi. So the altitude where the specification changes is 37,000 ft. This two-tier limit comes from how the aircraft is certified to handle pressurization loads across the flight envelope, balancing structural safety with the capabilities of the pressurization system at different cruise altitudes.