Instrument Landing System (ILS) Markers: Your Guide to a Safe Landing

What are the visual and aural indications when crossing the outer, middle, and inner markers of standard ILS?

A) Outer: Blue lights, "Marker Beacon"; Middle: Amber lights, "Marker Beacon"; Inner: White lights, "Marker Beacon"

B) Outer: White lights, "Marker Beacon"; Middle: Amber lights, "Marker Beacon"; Inner: Blue lights, "Marker Beacon"

C) Outer: Amber lights, "Marker Beacon"; Middle: Blue lights, "Marker Beacon"; Inner: White lights, "Marker Beacon"

D) Outer: Red lights, "Marker Beacon"; Middle: Green lights, "Marker Beacon"; Inner: Blue lights, "Marker Beacon"

Answer:

The visual and aural indications for the outer, middle, and inner markers of a standard ILS are white lights and 'marker beacon' respectively for the outer, amber lights and 'marker beacon' for the middle, and blue lights and 'marker beacon' for the inner.

Explanation:

The correct answer is B) Outer: White lights, 'Marker Beacon'; Middle: Amber lights, 'Marker Beacon'; Inner: Blue lights, 'Marker Beacon'. These are the standard visual and aural indications when crossing outer, middle, and inner markers of a standard Instrument Landing System (ILS). The purpose of these markers is to provide pilots with a means to verify their position along the approach path.

In general, the Outer Marker is located about 4–7 miles from the runway, providing a check point for the pilot to begin a descent from the approach altitude. The Middle Marker is much closer and usually signifies that it is safe to proceed with landing. Finally, the Inner Marker is usually close to the runway and indicates that the aircraft should be nearly ready to touch down, assuming the approach has been properly executed.