What does the middle marker beacon indicate?

The middle marker beacon indicates the aircraft's position when it is approximately 3,500 feet from the runway threshold during an ILS approach. When the middle marker beacon is activated, it typically provides an amber light and an audible tone to signify that the aircraft is nearing the decision height for landing. This indication assists pilots in determining whether they are on the correct approach path and prepares them for the critical phases of landing.

The amber light serves as a cautionary signal, alerting the crew to the proximity of the runway. The audible tone reinforces this indication, providing an additional sensory cue that is particularly useful in low visibility conditions. Understanding the function of the middle marker beacon is crucial for pilots to effectively manage their approach and landing procedures.