Plain English Meaning

A way for the aircraft's computer to fly a smooth, sloped descent to the runway by using the altimeter to know how high it is and the GPS to know where it is. Instead of stepping down level by level, the pilot follows a continuous descent path shown on the instruments.

Full Definition

A vertical navigation system that uses barometric altitude information from the aircraft's air data computer, combined with lateral guidance from an RNAV (typically GPS) source, to generate a computed vertical descent path on certain instrument approaches. The flight management system calculates a glidepath to the runway and displays vertical guidance to the pilot, allowing a to a published rather than a -down .