What effect does static port blockage have on the altimeter?

When the static port becomes blocked, it creates a situation where the altimeter is unable to receive accurate pressure input from the atmosphere. The altimeter measures altitude by comparing the ambient air pressure outside the aircraft with a pre-selected standard pressure setting, typically set to 29.92 inches of mercury (inHg).

When the static port is blocked, any change in altitude that occurs after the blockage will not affect the altimeter reading, as it will be unable to detect changes in atmospheric pressure. The altimeter will remain 'frozen' at the last indicated altitude at which the static port was unblocked and functioning correctly. This can cause confusion for the pilot because it may seem as if the aircraft is level, when in fact it could be climbing or descending.

This behavior is crucial for pilots to understand, as it affects navigation and safety; knowing that the altimeter is not providing current altitude information can impact decision-making during flight operations.