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 MIL-HDBK-1021/1
4.5.3
Clear Zones. These areas which include the overrun areas are shown in
Figures 13, 14, and 15. All airfields shall have clear zones. See Figures 9
through 11 for grades and Figure 12 for transverse section detail. Other
design criteria are shown in Table 5. The areas adjacent to the runway
thresholds require special restrictions to provide aircraft overrun areas and
unrestricted visibility of airfield lighting. To accomplish this, clear zones
are specified for each class of runway and further, the clear zone is
subdivided into Types I, II and III to define the degree of restrictive use.
The standards herein are in conformance with clear zone sizes specified in the
AICUZ program.
4.5.3.1 Clear Zone (Type I). This zone is immediately adjacent to the end of
the runway. It should be cleared, graded, and free of aboveground objects
(except airfield lighting) and is to receive special ground treatment or
pavement in the area designated as the runway overrun. This type clear zone is
required at both ends of all runways.
4.5.3.2 Clear Zone (Type II). This zone is used only for Class B runways and
is an extension of the Type I clear zone except that the width is reduced. The
Type II clear zone shall be graded and cleared of all aboveground objects
except airfield lighting.
4.5.3.3 Clear Zone (Type III). This zone is laterally adjacent to the Type II
clear zone for Class B runways and is used in lieu of the Type II clear zone at
Class A runways and basic training OLFs used by T-34 aircraft. Objects in this
zone shall not penetrate the approach-departure clearance surface. Trees,
shrubs, bushes, or any other natural growth shall be topped 10 feet below the
approach departure clearance surface or to a lesser height if necessary to
ensure visibility of airfield lighting. Buildings for human habitation shall
not be sited in the Type III clear zone even if they would not penetrate the
approach-departure clearance surface. The land in this type clear zone is best
utilized for agriculture or permanent open space exclusive of agricultural uses
which would attract birds or waterfowl. Land uses which would include human
activity for extended periods or group activities should be avoided. Traverse
ways (roads, railroads, canals, etc.,) are permitted provided they would not
penetrate airfield imaginary surfaces after the height of the traverse way has
been increased by the distances specified in Section II, paragraph B of NAVFAC
P-80.3.
4.5.3.4 Grading Requirements. The area to be graded is the Type I clear
zones. Grades are exclusive of the overrun, but are to be shaped into the
overrun grade. The maximum longitudinal grade change cannot exceed 2.0 percent
per 100 feet. The graded area is to be cleared and grubbed of stumps and free
of abrupt surface irregularities, ditches, and ponding areas. No aboveground
structures, objects, or traverse ways are permitted in the area to be graded,
but gentle swales, subsurface drainage, covered culverts, and underground
structures are permissible. The transition from the graded area to the
remainder of the clear zone is to be as gradual as feasible. No part of either
area can penetrate the approach-departure clearance surface. For policy
regarding permissible facilities, geographical features, and land use in the
remainder of the clear zone, refer to NAVFAC P-80.3. In addition, the Type II
clear zone shall be cleared and graded to generally follow the overrun profile.
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