Definition
The vertical guidance component of an Instrument Landing System (ILS), providing pilots with a precise descent path to the runway touchdown zone. The glide slope is transmitted as a radio beam from a ground-based transmitter located near the approach end of the runway, typically angled at 3 degrees above horizontal. Aircraft instruments display the aircraft's position above or below the correct descent path, allowing the pilot to fly a stabilized descent to the runway.
Plain English
An invisible, sloped radio beam that tells the pilot whether they're too high, too low, or right on the correct descent path to the runway during an instrument approach.
Context Anchor
You will see G/S during instrument approaches, especially when flying or briefing an instrument landing system approach.
Derivation
From 'glide' (a smooth, controlled descent) and 'slope' (an inclined line). Together they describe the gentle downward path the aircraft follows toward the runway — a sloped glide to landing.
Why Pilots Care
Staying on the glide slope keeps the aircraft on the safe descent angle that reaches the runway at the proper touchdown point.
Analogy
Think of the glide slope like an invisible ramp leading down to the runway. The aircraft is not riding on it, but the cockpit indication helps you stay aligned with that ramp.
Intuition Check
Glide slope does not mean the airplane must be gliding with no power. In this context, it means a vertical guidance path for descending to the runway.
Example Sentence 1
Once established on the localizer, the pilot intercepted the glide slope and began the descent toward the runway.
Example Sentence 2
A slight deviation below the G/S called for an immediate power adjustment.