The following civil airport imaginary surfaces are established with
relation to the airport and to each runway. The size of each such
imaginary surface is based on the category of each runway according to the
type of approach available or planned for that runway. The slope and
dimensions of the approach surface applied to each end of a runway are
determined by the most precise approach existing or planned for that
runway end.
(a) Horizontal surface. A horizontal plane 150 feet above the
established airport elevation, the perimeter of which is constructed by
swinging arcs of specified radii from the center of each end of the
primary surface of each runway of each airport and connecting the adjacent
arcs by lines tangent to those arcs. The radius of each arc is:
(1) 5,000 feet for all runways designated as utility or visual;
(2) 10,000 feet for all other runways. The radius of the arc specified
for each end of a runway will have the same arithmetical value. That value
will be the highest determined for either end of the runway. When a
5,000-foot arc is encompassed by tangents connecting two adjacent
10,000-foot arcs, the 5,000-foot arc shall be disregarded on the
construction of the perimeter of the horizontal surface.
(b) Conical surface. A surface extending outward and upward from
the periphery of the horizontal surface at a slope of 20 to 1 for a
horizontal distance of 4,000 feet.
(c) Primary surface. A surface longitudinally centered on a
runway. When the runway has a specially prepared hard surface, the primary
surface extends 200 feet beyond each end of that runway; but when the
runway has no specially prepared hard surface, or planned hard surface,
the primary surface ends at each end of that runway. The elevation of any
point on the primary surface is the same as the elevation of the nearest
point on the runway centerline. The width of a primary surface is:
(1) 250 feet for utility runways having only visual approaches.
(2) 500 feet for utility runways having nonprecision instrument
approaches.
(3) For other than utility runways the width is:
(i) 500 feet for visual runways having only visual approaches.
(ii) 500 feet for nonprecision instrument runways having visibility
minimums greater than three-fourths statute mile.
(iii) 1,000 feet for a nonprecision instrument runway having a
nonprecision instrument approach with visibility minimums as low as
three-fourths of a statute mile, and for precision instrument runways.
The width of the primary surface of a runway will be that width
prescribed in this section for the most precise approach existing or
planned for either end of that runway.
(d) Approach surface. A surface longitudinally centered on the
extended runway centerline and extending outward and upward from each end
of the primary surface. An approach surface is applied to each end of each
runway based upon the type of approach available or planned for that
runway end.
(1) The inner edge of the approach surface is the same width as the
primary surface and it expands uniformly to a width of:
(i) 1,250 feet for that end of a utility runway with only visual
approaches;
(ii) 1,500 feet for that end of a runway other than a utility runway
with only visual approaches;
(iii) 2,000 feet for that end of a utility runway with a nonprecision
instrument approach;
(iv) 3,500 feet for that end of a nonprecision instrument runway other
than utility, having visibility minimums greater than three-fourths of a
statute mile;
(v) 4,000 feet for that end of a nonprecision instrument runway, other
than utility, having a nonprecision instrument approach with visibility
minimums as low as three-fourths statute mile; and
(vi) 16,000 feet for precision instrument runways.
(2) The approach surface extends for a horizontal distance of:
(i) 5,000 feet at a slope of 20 to 1 for all utility and visual
runways;
(ii) 10,000 feet at a slope of 34 to 1 for all nonprecision instrument
runways other than utility; and,
(iii) 10,000 feet at a slope of 50 to 1 with an additional 40,000 feet
at a slope of 40 to 1 for all precision instrument runways.
(3) The outer width of an approach surface to an end of a runway will
be that width prescribed in this subsection for the most precise approach
existing or planned for that runway end.
(e) Transitional surface. These surfaces extend outward and
upward at right angles to the runway centerline and the runway centerline
extended at a slope of 7 to 1 from the sides of the primary surface and
from the sides of the approach surfaces. Transitional surfaces for those
portions of the precision approach surface which project through and
beyond the limits of the conical surface, extend a distance of 5,000 feet
measured horizontally from the edge of the approach surface and at right
angles to the runway centerline.