What do marker beacons indicate during an ILS approach?

Marker beacons are essential components of an Instrument Landing System (ILS) approach, providing pilots with specific information during the final phases of landing. The correct answer highlights their role in indicating the approach to decision height.

As an aircraft descends along the glideslope toward the runway, marker beacons signal the aircraft's position relative to its approach path. The outer marker typically indicates when the aircraft is approximately 5 miles from the runway and at a height of 200 feet above the decision height. The middle marker, on the other hand, usually indicates that the aircraft is at or near the decision height, where the pilot must determine whether to continue the approach or execute a missed approach depending on visual cues.

While airport location and distance to the runway could be inferred through other navigational aids, marker beacons specifically denote critical decision points during the approach, contributing to situational awareness and safety. Altitude restrictions are managed by the published approach procedures but are not directly communicated via marker beacons. Thus, the primary function of marker beacons during an ILS approach is to indicate the critical point of descent in relation to decision height.