In an Instrument Landing System (ILS), what is the function of the glide slope?

• A. It provides vertical guidance for descent along the glide path.
• B. It provides lateral guidance to the runway centerline.
• C. It transmits outer marker signals.
• D. It provides approach lighting information.

Answer: (A)

The glide slope provides vertical guidance for descent along the glide path. It creates a fixed descent angle (typically about 3 degrees) that the aircraft should follow to reach the runway smoothly. The ILS receiver in the airplane compares your current position to that glide path and shows you as above or below the path, prompting pitch adjustments to stay on course. This vertical guidance works together with the localizer, which handles lateral guidance to the runway centerline. The glide slope is not responsible for marker beacon signals or for the approach lighting system, which are separate components of the ILS and airport infrastructure.