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

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

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

Answer: (A)

The main idea is the extension rate of an approach surface—the ratio that tells how far outward the obstacle-free surface extends horizontally for each unit of vertical drop along the approach path. For non-precision approaches, there is no vertical guidance like a glide slope, so the surface that protects the approach path is designed with a relatively gentle expansion. This gentler extension rate creates a broader, flatter protection area, which is appropriate when descent guidance comes from a fixed, non-precision path rather than an aligned glide path. Among the given options, the correct choice is the one that corresponds to that gentler slope. The other rates imply steeper or otherwise inconsistent obstacle-clearance envelopes for non-precision approaches, which is why they don’t fit as well.

The main idea is the extension rate of an approach surface—the ratio that tells how far outward the obstacle-free surface extends horizontally for each unit of vertical drop along the approach path. For non-precision approaches, there is no vertical guidance like a glide slope, so the surface that protects the approach path is designed with a relatively gentle expansion. This gentler extension rate creates a broader, flatter protection area, which is appropriate when descent guidance comes from a fixed, non-precision path rather than an aligned glide path.

Among the given options, the correct choice is the one that corresponds to that gentler slope. The other rates imply steeper or otherwise inconsistent obstacle-clearance envelopes for non-precision approaches, which is why they don’t fit as well.