Blockages in the pitot-static system can cause which indications?

• A. For routine cruise maneuvers only
• B. Airflow over the wings increases
• C. Airspeed indicator and altimeter/VSI may show erroneous readings, including freezing or sticking
• D. The engine to surge

Answer: (C)

Blockages in the pitot-static system disrupt the pressure signals that the airspeed indicator, altimeter, and vertical-speed indicator rely on. The airspeed indicator uses dynamic pressure from the pitot port and static pressure to show speed. If the pitot tube is blocked, that dynamic pressure can’t reach the instrument, causing the needle to freeze or drift and often leading to readings that are unreal or stuck at a certain value. If the static ports are blocked, the altimeter and VSI lose the true ambient static pressure they need, so altitude and rate-of-climb indications can freeze or show erratic, out-of-scale readings. Because these systems feed the airspeed and altitude-related instruments, a single blockage can cause the airspeed indicator and the altimeter/VSI to display erroneous readings, including freezing or sticking. The other options describe effects that aren’t related to pressure signals from the pitot-static system, such as changes to wing airflow or engine behavior.