A14.2. Permissible Deviations from Design Criteria:
A14.2.1. Contents. This section furnishes siting information for airfield support facilities that may not
conform to the airfield clearance and airspace surface criteria elsewhere in this manual. This list is not
all-inclusive. Siting and design must either conform to this guidance or a waiver from the MAJCOM is
required. If the equipment renders satisfactory service at locations not requiring a clearance deviation,
such locations should be selected to enhance the overall efficiency and safety of airfield operations.
A184.108.40.206. Clear Zones are comprised of two separate areas that are treated differently. This is
because initially, the area known as the Clear Zone was defined as; "the areas immediately
adjacent to the ends of a runway, which have been cleared of all above ground obstructions and
graded to minimize damage to aircraft that undershoot or overrun the runway." At that time, the
geometric requirements for the Clear Zone were 2,000 feet wide and 1,000 feet long. In 1974,
DoD implemented a requirement for the services to control development in near vicinity to military
airfields to protect the safety, health and welfare of personnel on base, and in the surrounding
communities. This action was also intended to preserve maximum mission flexibility. To
accommodate these needs, the Clear Zone size was expanded and the allowable uses were
published within the Air Installation Compatible Use Zone Program guidance, currently AFI 32-
7063. It is important to understand that all objects located within the expanded area of Clear Zones
are not necessarily obstructions, and there are no specific grading requirements for this area.
Review current AICUZ criteria for land uses in this area before initiating waivers. Items listed
within this attachment may be sited in the Clear Zone without waiver as long as all siting criteria
A14.2.2. Frangibility Requirements. All structures placed or constructed within the airfield
environment must be made frangible (to the maximum extent practicable) or placed below grade
unless otherwise noted in the definitions that follow, or unless specifically described as exempt from
frangibility requirements using the siting criteria in this manual. This applies for any above ground
construction that is within 250 feet of the runway centerline and an extension of that dimension for
3,000 feet beyond the ends of the runway thresholds and within 200 feet of the taxiways, but is
limited to structures owned or controlled by DoD. Frangibility implies that an object will collapse
or fall over after being struck by a moving aircraft with minimal damage to the aircraft. The
constructed object must not impede the motion or radically alter the path of the aircraft.
Foundations for frangible structures shall be constructed flush with finished grade and the
surrounding soil shall be compacted. Corrective action is required if more than three-inches of the
vertical surface of any foundation is exposed above finish grade. All structures shall be designed to
allow performance of the structure to withstand wind loads less than 70 MPH. At wind speeds and
icing conditions above permissible airfield operations conditions, deflections shall remain within the
elastic performance of the structure. This concept does not include structures intended to house
people. Integral fuel tanks should be used for necessary emergency power generator sets. If additional
fuel storage tanks are required, they should be placed below grade along with other supporting utilities.
A220.127.116.11 Essentially, there are three types of frangible devices and structures. These are normally
related to the height of the structure. They are described below.
A18.104.22.168.1. Frangible Support -- A support for elevated fixtures or other devices composed
of a supporting element with a fracture mechanism at its base. It is designed to present a
minimum of mass and to break at the base when impacted. Normally used when the
mounting height is 2 meters (6 feet) or less above the mounting surface.