Travis AFB Sustainability Study Report Final Background Report | Page 244
As defined in the Travis AFB AICUZ, the following provides a description of
each of the imaginary surfaces.
Primary Surface. This surface defines the limits of the obstruction clearance
requirements in the immediate vicinity of the landing area. The primary
surface comprises surfaces of the runway, runway shoulders, and lateral
safety zones and extends 200 feet beyond the runway end. The width of the
primary surface for the type of runway at Travis AFB is 2,000 feet, or
1,000 feet on each side of the runway centerline.
Clear Zone Surface. This surface defines the limits of the obstruction
clearance requirements in the vicinity contiguous to the end of the primary
surface. The length and width (for a single runway) of a Clear Zone surface at
Travis AFB is 3,000 feet by 3,000 feet.
Approach‐Departure Clearance Surface. This surface is symmetrical about
the runway centerline extended, begins as an inclined plane (glide angle)
200 at the end of the primary surface of the centerline elevation of the
runway end, and extends for 50,000 feet. The slope of the
approach‐departure clearance surface is 50:1 along the extended runway
(glide angle) centerline until it reaches an elevation of 500 feet above the
established airfield elevation. It then continues horizontally at this elevation
to a point 50,000 feet from the start of the glide angle. The width of this
surface at the runway end is 2,000 feet; it flares uniformly, and the width at
50,000 feet is 16,000 feet.
Inner Horizontal Surface. This surface is a plane, oval in shape at a height of
150 feet above the established airfield elevation. It is constructed by scribing
an arc with a radius of 7,500 feet above the centerline at the end of the
runway and interconnecting these arcs with tangents.
Figure 5.23‐1.
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Conical Surface. This is an inclined surface extending outward and upward
from the outer periphery of the inner horizontal surface for a horizontal
distance of 7,000 feet to a height of 500 feet above the established airfield
elevation. The slope of the conical surface is 20:1.
Example Imaginary Surfaces Cross‐Section
Compatibility Assessment