Definition
An autopilot mode that captures and tracks the vertical guidance signal of an Instrument Landing System (ILS), holding the aircraft on the published descent path to the runway. Once armed and the glideslope signal is received, the autopilot transitions from its previous vertical mode and adjusts pitch to keep the aircraft on the glideslope until disengagement at minimums or go-around.
Plain English
A setting on the autopilot that lets the airplane follow the invisible sloped beam coming up from the runway, so it descends at the right angle for landing without the pilot flying it by hand.
Context Anchor
Seen during instrument approaches and in autopilot mode indications, especially when the airplane is set up to follow vertical guidance down to a runway.
Derivation
‘Glide’ refers to a steady descent without added power, and ‘slope’ describes the angled path. Together the term describes the sloped descent path the aircraft follows down to the runway.
Why Pilots Care
Staying on the glideslope keeps the aircraft on a safe path to the runway; large deviations can result in an unstabilized approach or landing short of the threshold.
Grounding Statement
Picture a slanted invisible path leading from the airplane’s position down to the runway; G/S is the guidance that helps the airplane stay on that path.
Intuition Check
G/S does not mean the physical slope of the runway. It means the vertical guidance path the airplane follows down toward the runway.
Example Sentence 1
After intercepting the localiser, the crew armed G/S and watched the autopilot capture the glideslope at the published altitude.
Example Sentence 2
We were slightly high on the glideslope and reduced power to correct.