Plain English Meaning

A system in the aircraft that uses the altimeter, plus information from the flight computer, to draw a sloping descent path down to the runway and keep the airplane on it. It works like a built-in glide path, but it relies on air pressure rather than a ground signal.

Full Definition

A vertical navigation system that uses barometric altitude (pressure altitude corrected by the local altimeter setting) to compute and display a descent path, allowing the aircraft to fly a published vertical profile on certain RNAV approaches such as LNAV/VNAV. The calculates the required vertical path between defined and provides guidance to keep the aircraft on that path, with dependent on a and on within the published limits for the .