Career Enlisted Aviator (CEA) Fundamentals Block 5 Practice Test

An altimeter reads height by sensing ambient pressure and then translating that pressure into a reading with a mechanical linkage. The input it relies on is the measured atmospheric pressure level—the actual pressure at the aircraft’s location. The indication is produced by the mechanical displacement of the indicator needles, which move as the pressure within the capsule changes. The altimeter setting acts as the reference pressure you dial in; changing this setting shifts the displayed altitude so the instrument aligns with the correct reference (for example, sea level pressure). Air density, while it affects how pressure changes with height in the real atmosphere and can cause the indicated altitude to differ from true altitude under nonstandard conditions, is not directly used by the altimeter to determine its indication.