Which surface extends upwards/outwards at 20:1 for its growth?

Which surface extends upwards/outwards at 20:1 for its growth?

• A. Conical surface
• B. Primary surface
• C. Transitional surface
• D. Approach surface

Answer: (A)

In airport obstacle control, several surfaces protect airspace around a runway. The surface that grows upward and outward with a fixed ratio of growth is the conical surface. It extends away from the end of the runway, rising as distance from the runway increases, with a slope of 20:1. That means for every 20 units of horizontal distance from the runway end, the allowable height increases by 1 unit, forming a cone-shaped area. This setup provides a gradual, predictable limit to obstacle heights as you move away from the runway end, helping ensure safe clearance for aircraft at various positions along the approach and beyond. Other surfaces, like the approach, transitional, or primary surface, have different shapes and purposes and do not use the 20:1 growth ratio.

In airport obstacle control, several surfaces protect airspace around a runway. The surface that grows upward and outward with a fixed ratio of growth is the conical surface. It extends away from the end of the runway, rising as distance from the runway increases, with a slope of 20:1. That means for every 20 units of horizontal distance from the runway end, the allowable height increases by 1 unit, forming a cone-shaped area. This setup provides a gradual, predictable limit to obstacle heights as you move away from the runway end, helping ensure safe clearance for aircraft at various positions along the approach and beyond. Other surfaces, like the approach, transitional, or primary surface, have different shapes and purposes and do not use the 20:1 growth ratio.