For a precision approach, what is the rate of the approach surface extension?

For a precision approach, what is the rate of the approach surface extension?

• A. 20:1
• B. 34:1
• C. 7:1
• D. 50:1

Answer: (D)

The surface extension rate describes how the protected area alongside the final approach path grows as you move away from the runway threshold. For precision approaches, this extension follows a slope of 50 horizontal to 1 vertical. In other words, for every 50 feet of horizontal distance from the threshold, the protected surface rises by 1 foot. This shallow, wide extension is designed to keep the approach path clear of obstacles at all points where precision guidance is used, supporting accurate vertical and lateral guidance down to the runway. For example, at 5,000 feet from the threshold, the protected surface is 100 feet above the runway elevation (5,000 ÷ 50 = 100).

The surface extension rate describes how the protected area alongside the final approach path grows as you move away from the runway threshold. For precision approaches, this extension follows a slope of 50 horizontal to 1 vertical. In other words, for every 50 feet of horizontal distance from the threshold, the protected surface rises by 1 foot.

This shallow, wide extension is designed to keep the approach path clear of obstacles at all points where precision guidance is used, supporting accurate vertical and lateral guidance down to the runway. For example, at 5,000 feet from the threshold, the protected surface is 100 feet above the runway elevation (5,000 ÷ 50 = 100).