Which situation leads to the Altimeter not changing when the Pitot Static system is blocked?

When the Pitot Static system is blocked, the altimeter's functionality is directly impacted because the altimeter relies on ambient static pressure for accurate readings. In this scenario, if the Pitot tube is blocked, it would prevent the airspeed indicator from providing accurate airspeed information but does not necessarily stop the altimeter from receiving static pressure. However, if the entire Pitot Static system is blocked, the altimeter becomes unable to sense changes in ambient pressure, leading to a scenario where the altimeter does not change even when altitude changes occur.

In a blocked Pitot Static condition, both the static and dynamic pressures are impacted. The altitude indication becomes frozen at the last known value because the altimeter only measures static pressure, which will remain unchanged if the static source cannot vent to the outside atmosphere. Thus, the altimeter becomes unreliable until the blockage is resolved, meaning the reading will not change as you ascend or descend.

The other situations—such as a blocked Pitot tube specifically—impact different instruments like the airspeed indicator. Lag error refers to the delay in the instrument’s response, while position error relates to discrepancies from actual altitude due to instrument design or position of static sources. However, these issues do not result in the altimeter being