b. Federal Aviation Regulation-77, Section 77.29, Airport Imaginary Surfaces for Heliports. These
surfaces apply to all military heliports. For the purpose of this section, a military heliport is any heliport
operated by an armed force of the US.
A heliport primary surface is an area of the primary surface which coincides in size and
shape with the designated takeoff and landing area of a heliport. This surface is a horizontal
plane at the elevation of the established heliport elevation.
A heliport approach surface begins at each end of the heliport primary surface, is the same
width as the primary surface, and extends outward and upward for a horizontal distance of
4,000 feet where its width is 500 feet. The slope of the approach surface is 8:1 for civil
heliports and 10:1 for military heliports.
A heliport transitional surface extends outward and upward from the lateral boundaries of the
heliport primary surface and from the approach surfaces at a slope of 2:1 for a distance of
250 feet measured horizontally from the centerline of the primary and approach surfaces.
c. Federal Aviation Regulation-77, Section 77.5, Kinds of Objects Affected. This section further
defines an obstruction and applies to--
Any object of natural growth, terrain, or permanent or temporary construction or alteration
(including equipment or materials used therein) and apparatus of a permanent or temporary
The alteration of any permanent or temporary existing structure by a change in its height
(including appurtenances) or lateral dimensions (including equipment or materials used
6-3. Airport Data. The ARP location (in degrees, minutes, and seconds
of longitude and latitude)
determined according to FAA 405. Field elevation is the highest point on any airport landing surface.
PART B - AIRFIELD DATA ACCURACY REQUIREMENTS
All contiguous CONUS, Alaskan, and
Caribbean coordinates are determined
based on NAD 83 and/or WGS 84. Geodetic accuracy of orthometric heights is referenced to the North
American Vertical Datum of 1988 (NAVD 88). The coordinates for the points on the airport require
different degrees of accuracy. Tables 6-1 through 6-5, pages 6-9 and 6-10, are examples of different
accuracy standards for airfield data. FAA 405 contains the complete requirements.