Definition
The vertical guidance signal provided by the glideslope component of an Instrument Landing System (ILS), giving pilots a precise descent path to the runway during an instrument approach. The glideslope transmitter, located near the touchdown zone, projects a narrow radio beam upward at a fixed angle (typically 3 degrees) that the aircraft's ILS receiver interprets and displays on the cockpit instruments, showing whether the aircraft is on, above, or below the correct descent path.
Plain English
A radio signal at the runway that tells the pilot whether they are descending at the right angle to land. The cockpit display shows a needle the pilot keeps centered to stay on the correct slope down to the runway.
Context Anchor
Pilots encounter ILS glideslope guidance during instrument approaches, especially when clouds or low visibility make it hard to judge the descent path by looking outside.
Derivation
ILS stands for Instrument Landing System. 'Glideslope' combines 'glide' (a controlled descent) and 'slope' (an inclined path), describing the angled descent path the signal defines.
Why Pilots Care
Allows safe, precise landings in low visibility and prevents descent below the correct glide path into terrain.
Intuition Check
ILS glideslope guidance does not steer or land the airplane by itself. It gives the pilot vertical path information so the pilot can correct the descent if the airplane is too high or too low.
Example Sentence 1
Cleared for the ILS approach to runway 27, the pilot intercepted the glideslope guidance and began a steady descent toward the runway.
Example Sentence 2
When the ILS glideslope guidance became unreliable, the crew executed a missed approach.