Which of the following statements best describes the relationship between the normal and maximum cabin differential pressures?

• A. The difference is 0.1 psi
• B. The difference is 1.0 psi
• C. The difference is 0.5 psi
• D. The difference is 2.0 psi

Answer: (A)

Normal cabin differential is the pressure difference the pressurization system actively maintains for passenger comfort, while the maximum cabin differential is the structural limit the airframe can safely withstand. The two values are kept very close so the cabin stays comfortable but the airframe isn’t pushed toward its limit during transient changes. A tiny margin, about 0.1 psi, provides just enough headroom for brief fluctuations (like valve cycling or small altitude transients) without risking structural overload. Larger margins would allow larger pressure excursions that could approach unsafe levels during abnormal operations.