[Code of Federal Regulations]
[Title 14, Volume 2]
[Revised as of January 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR77.25]

[Page 163-164]
 
                     TITLE 14--AERONAUTICS AND SPACE
 
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION 
                               (CONTINUED)
 
PART 77_OBJECTS AFFECTING NAVIGABLE AIRSPACE--Table of Contents
 
                     Subpart C_Obstruction Standards
 
Sec.  77.25  Civil airport imaginary surfaces.

    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;

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    (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.

[Doc. No. 10183, 36 FR 5970, Apr. 1, 1971; 36 FR 6741, Apr. 8, 1971]