primary surface

primary surface

A rectangular surface longitudinally centered about a runway. Its width is a variable dimension, and it usually extends 200 ft (60 m) beyond each end of the runway when the runway has a specially prepared hard surface. When the runway has no specially prepared or planned hard surface, the primary surface ends at each end of that runway. The elevation of any point on this surface coincides with the elevation of the nearest point on the runway centerline or the extended runway centerline.