[Code of Federal Regulations]

[Title 14, Volume 2]

[Revised as of January 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 14CFR77.28]



[Page 188-189]

 

                     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. 77.28  Military airport imaginary surfaces.



    (a) Related to airport reference points. These surfaces apply to all 

military airports. For the purposes of this section a military airport 

is any airport operated by an armed force of the United States.

    (1) Inner horizontal surface. A plane is oval in shape at a height 

of 150 feet above the established airfield elevation. The plane is 

constructed by scribing an arc with a radius of 7,500 feet about the 

centerline at the end of each runway and interconnecting these arcs with 

tangents.

    (2) Conical surface. A surface extending from the periphery of the 

inner horizontal surface outward and upward at a slope of 20 to 1 for a 

horizontal distance of 7,000 feet to a height of 500 feet above the 

established airfield elevation.

    (3) Outer horizontal surface. A plane, located 500 feet above the 

established airfield elevation, extending outward from the outer 

periphery of the conical surface for a horizontal distance of 30,000 

feet.

    (b) Related to runways. These surfaces apply to all military 

airports.

    (1) Primary surface. A surface located on the ground or water 

longitudinally centered on each runway with the same length as the 

runway. The width of the primary surface for runways is 2,000 feet. 

However, at established bases where substantial construction has



[[Page 189]]



taken place in accordance with a previous lateral clearance criteria, 

the 2,000-foot width may be reduced to the former criteria.

    (2) Clear zone surface. A surface located on the ground or water at 

each end of the primary surface, with a length of 1,000 feet and the 

same width as the primary surface.

    (3) Approach clearance surface. An inclined plane, symmetrical about 

the runway centerline extended, beginning 200 feet beyond each end of 

the primary surface at the centerline elevation of the runway end and 

extending for 50,000 feet. The slope of the approach clearance surface 

is 50 to 1 along the runway centerline extended until it reaches an 

elevation of 500 feet above the established airport elevation. It then 

continues horizontally at this elevation to a point 50,000 feet from the 

point of beginning. The width of this surface at the runway end is the 

same as the primary surface, it flares uniformly, and the width at 

50,000 is 16,000 feet.

    (4) Transitional surfaces. These surfaces connect the primary 

surfaces, the first 200 feet of the clear zone surfaces, and the 

approach clearance surfaces to the inner horizontal surface, conical 

surface, outer horizontal surface or other transitional surfaces. The 

slope of the transitional surface is 7 to 1 outward and upward at right 

angles to the runway centerline.



[Doc. No. 1882, 30 FR 1839, Feb. 10, 1965, as amended by Amdt. 77-1, 30 

FR 6713, May 18, 1965; Amdt. 77-9, 36 FR 5971, Apr. 1, 1971]