updated to meet DoD specifications. This would include the addition of a clear zone (CZ),
accident potential zone I (APZ I), and accident potential zone II (APZ II), which are larger
than the existing RPZ established by the FAA. Each of these zones have their own set of
suggested land use compatibility guidelines and are developed based on a statistical
review of aircraft accidents. DoD Instruction 4165.57 recommends that no development
be located within the CZ.
An example CZ has been provided on Figure 5‐20. The CZ shown is not an official DoD
approved clear zone and was developed based on runways of similar sizes as the runway
at Pinal Airpark. Should a runway expansion occur at the airpark, modeling will need to
be completed to develop official safety zones.
As Figure 5‐20 shows, the example CZ extends extensively over SBAH covering nine
existing buildings, including the SBAH fire station, the WAATS Enlisted Training Center, a
Readiness Center, and a field maintenance shop.
5.17
Vertical Obstructions (VO)
Vertical obstructions are created by buildings, trees, structures, or other features that
may encroach into the navigable airspace or line‐of‐sight of radar signal transmission
pathways used by the military. These obstructions can be a safety hazard to both military
personnel and the public, with subsequent potential adverse impacts to military
readiness. Vertical obstructions can compromise the value of low‐level flight training by
limiting the areas where such training can occur. Obstructions can include a range of
items from man‐made, such as buildings, telephone poles, utility transmission towers,
and radio antennas, to natural, such as tall trees and land features. Vertical obstructions
can also interfere with radar transmissions, compromising the integrity of data
transmission between the transmitter and receiver. Though most critical near the
transmitter, the geographic area impacting the transmissions, or radar viewshed, can be
broad depending on the distance between the transmitter and receiver.
Two issues relating to Vertical Obstructions have been
identified as part of this JLUS.
VO-1 Future power transmission line projects could pose helicopter
flight hazards.
VO-2 Cellular communication towers may generate obstructions to
flight operations.
Background Report
5-131