In an ILS approach, what does the middle marker signify?

The middle marker on an Instrument Landing System (ILS) approach plays a crucial role in providing pilots with specific guidance during the final stages of landing. It indicates the location associated with the decision height — the altitude at which a pilot must decide whether to continue the approach for landing or execute a missed approach.

The decision height is a critical point for pilots; at this altitude, they must have visual references to proceed with the landing. If visual cues are insufficient, the proper action is to initiate a missed approach. The middle marker generally provides an audio or visual signal, reinforcing the importance of this decision point during low visibility conditions.

Understanding this marker's function helps pilots make informed decisions and enhances safety during ILS approaches, particularly when landing in challenging weather conditions.