What is the outer marker (OM) threshold distance range from the threshold?

The outer marker (OM) is a key component of the Instrument Landing System (ILS), specifically used for precision approaches in aviation. It provides a distinct point in the approach procedure, typically indicating the point at which an aircraft is approximately 4 to 7 nautical miles from the runway threshold. This distance helps pilots understand their position on the approach path and aids in timing their descent and preparing for landing.

In practice, the OM serves as a useful cue for pilots to switch their approach from the en route phase to the final approach phase, ensuring they are descending properly in line with the glide slope. Recognizing the 4-7 NM range ensures that pilots maintain adequate situational awareness and can prepare appropriately for landing, including configuring the aircraft and confirming settings.

Understanding the significance of the OM threshold distance allows pilots to follow proper protocols during an approach, ultimately enhancing safety and efficiency in landing procedures.