92 Ill. Adm. Code 16.50
Horizontal Surface
Section 16.50 Horizontal Surface
A horizontal surface is a plane 150 feet above the
established airport elevation.
a) The
perimeter of a horizontal surface is constructed by swinging arcs of specified
radii from the center of each end of the primary surface of each runway and
connecting the adjacent arcs by lines tangent to those arcs. The radii of each
arc is:
1) 5,000 feet for all
runways designated as utility or visual; and
2) 10,000 feet for all
other runways.
b) The
radius of the arc specified for each end of a runway will have the same
arithmetical value. That value will be the highest value determined for either
end of the runway.
c) When
tangents connecting two adjacent 10,000-foot arcs encompass a 5,000-foot arc,
the 5,000-foot arc shall be disregarded on the construction of the perimeter of
the horizontal surface.
d) The
horizontal surface does not include the approach surface (see Section 16.80)
and transitional surfaces (see Section 16.90).
e) Under
Departmental standards, a horizontal surface is defined as a circle (radius
5,000 feet) with the center being the ARP.