Definition: approach surfaces (Applicable to Article VI - Chapter 1)
The "approach surfaces" are imaginary inclined planes, trapezoidal in shape and located symmetrically with respect to the extended center line of any runway. Such approach surfaces , extending from both ends of any runway, consist of contiguous inner and outer sections whose dimensions are as follows: (a) The plane of the inner section: (1) begins at a line drawn parallel to, and at the same elevation as, the end of the runway, and at a distance, measured horizontally along the extended runway centerline, of 200 feet from the end of the runway; (2) extends for a distance of 10,000 feet, measured horizontally along the extended runway centerline; (3) has a width of 1,000 feet measured along the line described in paragraph (a)(1) of this Section, which increases uniformly (with respect to the extended runway centerline) to a width of 4,000 feet at the outer edge of such inner section, as described in paragraph (a)(2) of this Section; and (4) rises at a slope of one foot in height for every 50 feet of horizontal distance. (b) The plane of the outer section: (1) begins at the outer edge of the inner section; (2) extends for a distance of 15,000 feet, measured horizontally along the extended runway centerline; (3) has a width of 4,000 feet commencing at the outer edge of the inner section, which increases uniformly (with respect to the extended runway center line) to a width of 8,500 feet at the outer edge of such outer section; and (4) rises at a slope of one foot in height for every 40 feet of horizontal distance. DESCRIPTION OF APPROACH SURFACE