Definition
The vertical guidance component of an Instrument Landing System (ILS), providing a precise descent path — typically 3 degrees — from the final approach fix down to the runway touchdown zone. It is transmitted as a radio beam from a ground antenna near the approach end of the runway, and the aircraft's receiver displays deviation above or below the path on the cockpit indicator.
Plain English
An invisible, slanted radio beam that guides a pilot down at the correct angle to land on the runway. The cockpit instrument shows whether the aircraft is too high, too low, or right on the path.
Context Anchor
Seen on instrument approach charts and cockpit instruments during approaches that provide vertical guidance to a runway.
Derivation
From 'glide' (to descend smoothly without power input) and 'slope' (an inclined line). Together: the inclined path an aircraft glides down toward the runway. The plain-language origin matches the aviation meaning closely.
Why Pilots Care
Staying on the glideslope ensures obstacle clearance and places the aircraft in the correct position to land safely on the runway.
Intuition Check
A glideslope is not the whole approach and it does not steer the airplane left or right. It gives vertical guidance only: high, low, or on the downward path.
Example Sentence 1
Approaching the final approach fix, the pilot intercepted the glideslope and began a steady descent toward the runway.
Example Sentence 2
A full deflection below the glideslope means the aircraft is too low and must climb to regain the path.