Plain English Meaning

A way of showing the pilot a steady descent path during an approach, where the up-and-down position is worked out from the cabin pressure altimeter instead of from GPS height. As long as the altimeter setting is right and the air isn't too cold, it gives a smooth path down to the runway.

Full Definition

A navigation system that computes a vertical glidepath on an instrument approach using altitude information derived from the aircraft's barometric altimeter rather than from -based . It presents the pilot with a descent path that can be flown with to onboard equipment, provided the altimeter setting is and the is within the approach's published limits.