What is a characteristic of the middle marker (MM) on an ILS approach?

The middle marker (MM) on an Instrument Landing System (ILS) approach is characterized by its unique audio and visual signals used to indicate the aircraft's position during the approach. Specifically, the correct response highlights that the middle marker emits an alternating series of dots and dashes represented by an amber light.

The alternating dot-and-dash signal is designed to alert pilots that they are at a specific point along the approach path, typically about 3,500 feet from the runway threshold. This is crucial for pilots as it helps them determine their distance to the runway and aids in decision-making at a critical phase of flight.

In contrast, the continuous tone associated with the outer marker is represented as blue, while low-pitched dashes and high-pitched dots pertain to the inner marker's signaling methods and are not characteristics of the middle marker. Understanding these characteristics is vital for safe and precise navigation during ILS approaches.