What is the maximum error an altimeter can indicate before it is removed from service?

The maximum allowable error for an altimeter before it must be removed from service is indeed 20 feet. This standard aligns with FAA regulations, which stipulate that altimeters used in aircraft must meet specific accuracy requirements to ensure safe altitude measurements. An altimeter that indicates an error greater than 20 feet could lead to dangerous situations, such as flying at unsafe altitudes, especially in areas of terrain, congestion, or regulated airspace.

Ensuring accurate altitude readings is critical for safe flight operations, particularly during takeoff, landing, and in-flight navigation. Maintaining operational altimeters within this specified accuracy limit promotes safety and compliance with aviation regulations.