What are the primary components of an Instrument Landing System (ILS)?

• A. Localizer, glide slope, outer and middle/inner markers or marker beacons, and approach lighting.
• B. Localizer only.
• C. Glide slope and approach lighting only.
• D. Marker beacons only.

Answer: (A)

An Instrument Landing System provides both lateral and vertical guidance plus visual cues to help a pilot land in low visibility. The main parts are the localizer, which gives horizontal guidance by keeping you on the runway centerline, and the glide slope, which provides a controlled vertical descent along a standard approach path. Along the approach, marker beacons (outer and middle, sometimes an inner marker) indicate fixed distances from the runway threshold and help confirm you’re in the correct position on the approach. The approach lighting system extends from the runway to help you visually acquire and align with the runway as you break out of the clouds. Without any one of these elements, the system wouldn’t provide the full precision guidance needed for safe instrument approaches.