During cabin pressurization, why might static pressure readings be affected?

• A. Because pitot tube heats up.
• B. Because altitude changes rapidly.
• C. Because cabin differential pressure can affect static pressure readings.
• D. Because the airplane slows down.

Answer: (C)

Static pressure readings depend on the ambient air pressure around the aircraft, not on the cabin pressure. When the cabin is pressurized, the difference between inside and outside air (the differential pressure) alters the airflow and pressure distribution around the fuselage. This disturbance around the static ports can cause the readings to differ from true outside ambient pressure, so the static pressure shown by the system can be affected during cabin pressurization.