Definition
Cockpit instruments or display elements that show the aircraft's vertical position relative to the published glide path during an instrument approach, typically the glide slope component of an Instrument Landing System (ILS). The indicator displays a horizontal needle or bar that moves up when the aircraft is below the glide path and down when above it, allowing the pilot to fly a stable descent to the runway.
Plain English
Instruments that tell the pilot whether they are too high, too low, or right on the correct descent path to the runway during an instrument approach.
Context Anchor
Seen on navigation instruments during an instrument landing system approach, especially when the pilot is using vertical guidance to descend toward the runway.
Derivation
Glideslope' combines 'glide' (a smooth descending flight path) with 'slope' (an inclined line). The indicator shows where the aircraft sits relative to that sloped descent path.
Why Pilots Care
They allow immediate correction of glide path to avoid obstacles and achieve a safe touchdown point.
Intuition Check
Do not think of glideslope indicators as controlling the airplane. They only show where the airplane is relative to the desired descent path; the pilot or autopilot must make the corrections.
Example Sentence 1
As the aircraft intercepted the final approach course, the pilot watched the glideslope indicator center and began a steady descent toward the runway.
Example Sentence 2
At night the glideslope indicators provided clear visual guidance all the way to the runway threshold.