If the static port is blocked, what will happen to the altimeter?

When the static port is blocked, the altimeter will freeze at the last altitude it was indicating at the time of the blockage. This occurs because the altimeter relies on static pressure from the atmosphere to provide accurate altitude readings. If the static port becomes obstructed, there is no longer a way for the altimeter to equalize with the external atmospheric pressure, preventing it from accurately registering changes in altitude. As a result, the altimeter will reflect a constant value, essentially "freezing" at the altitude it displayed before the blockage occurred.

The other potential outcomes, such as random fluctuations, a gradual decline, or over-reading, would typically not occur given the nature of the static pressure system and how altimeters are designed to function. Fluctuations would imply some external pressure changes that are not possible with a blocked static port, while a gradual decline or over-reading would suggest the altimeter is adjusting to changing conditions, which it cannot do once restricted by the blockage.