What are the colors and significance of the marker beacons?

• A. Outer Marker: Blue, GS intercept (low pitched); Middle Marker: Orange, DH (medium pitched); Inner Marker: White, CAT II DH (high pitched)
• B. Outer Marker: Red; GS intercept (low pitched); Middle Marker: Orange, DH (medium pitched); Inner Marker: White, CAT II DH (high pitched)
• C. Outer Marker: Blue; GS intercept (high pitched); Middle Marker: White, DH (low pitched); Inner Marker: Orange, CAT II DH (medium pitched)
• D. Outer Marker: White; GS intercept (low pitched); Middle Marker: Orange, DH (medium pitched); Inner Marker: Blue, CAT II DH (high pitched)

Answer: (A)

Marker beacons provide visual and audio cues along an ILS to help you identify your position on the approach. The outer marker is shown by a blue light and a low-pitched tone, and it marks where you intercept the glide slope. Closer in, the middle marker is amber with a medium-pitched tone, giving another reference point as you descend along the glide slope. Near the runway, the inner marker is white with a high-pitched tone; it is used on CAT II/III approaches to indicate the decision height. If you reach the inner marker, you should have the required visual cues to continue to land or execute a missed approach if those cues aren’t present.