What happens to the ASI/Mach meter during a climb when the static probe is blocked?

When the static probe becomes blocked during a climb, the ASI (Airspeed Indicator) and Mach meter will respond differently than under normal conditions. The ASI relies on static pressure, which is used to determine the difference between dynamic pressure (from the pitot tube) and static pressure. If the static probe is blocked, the static pressure reading will remain constant, which does not accurately reflect the actual altitude change.

In a climb, outside air pressure decreases, leading to a decrease in static pressure. However, if the static probe is blocked, the ASI continues to read based on its last known static pressure input, which is higher than the actual static pressure at the new altitude. As a result, the ASI/Mach meter will read higher than it should, leading to an over-reading of airspeed. This phenomenon arises due to the discrepancy between the actual decreasing static pressure and the stale, incorrect static pressure that the ASI is measuring from the blocked probe.

Understanding this situation is critical for pilots as it emphasizes the importance of ensuring pitot-static systems are functioning correctly during flights, especially during altitude changes.