Plain English Meaning

Small reading errors that come from the way the altimeter is built, not from the weather or how it was set. The internal parts can lag, stick, or briefly read the wrong way, especially during rapid climbs, descents, or sharp pitch changes.

Full Definition

Inaccuracies in altimeter indication caused by the physical and mechanical limitations of the instrument itself, rather than by atmospheric conditions or pilot setting errors. These include scale error (the altimeter reading differs from true pressure altitude even when correctly set), hysteresis (a lag in the response of the aneroid wafers after a rapid altitude change), reversal error (a momentary indication in the wrong direction during abrupt pitch changes), and friction error (the pointer sticking briefly due to internal mechanical ).