Part B-Airfield Data Accuracy Requirements

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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

character.

 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

therein).

6-3. Airport Data. The ARP location (in degrees, minutes, and seconds of longitude and latitude) is

determined according to FAA 405. Field elevation is the highest point on any airport landing surface.

PART B - AIRFIELD DATA ACCURACY REQUIREMENTS

6-4. 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.

EN0593

6-8

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