Airfield Safety MCA Subzone B (APZ)
Subzone B includes all land outside the installation boundary within the APZs.
Compatibility guidelines recommend land uses that concentrate large numbers of people
(such as residences, apartments, churches, and schools) not be constructed within the
APZs. While the likelihood of an accident is remote, the military recommends low density
land uses within the APZs to ensure the maximum protection of public health and
property.
Airfield Obstructions MCA (Figure 26)
The Silverbell Army Heliport Airfield Obstructions MCA includes all land outside the
installation boundaries within the imaginary surfaces around the helicopter landing pads.
The purpose of the Airfield Obstructions MCA is to manage the height of all structures
and buildings within the area defined by Federal Aviation Administration (FAA) and DoD
guidance known as imaginary surfaces. The imaginary surfaces are 3-D geographic areas
comprising approach‐departure airspace corridors and safety buffers. Vertical
obstruction heights are a major concern for flight operations and training due to the
potential for a structure to extend into navigable airspace, which could impede safe flight
operations and put both pilots and citizens on the ground at risk of an aircraft accident.
Vertical obstructions that can affect flight safety include, but are not limited to, cell
towers, power lines, wind turbines, buildings, and trees. This MCA has two subzones.
Airfield Obstructions MCA Subzone A
Subzone A is composed of the approach‐departure clearance surfaces for the landing
pads. These begin as inclined planes at the end of the primary surface and extend for
1,200 feet. The slope of the approach‐departure clearance surface is 8:1. The width of
this surface at the primary surface is 300 feet, widening uniformly to a width of 600 feet
at the end point.
Airfield Obstructions MCA Subzone B
Subzone B is composed of the transitional surfaces for the landing pads. The transitional
surface extends outward and upward at right angles to the primary surface and extended
landing lane at a slope of 2:1. The transitional surface starts at the lateral edges of the
primary surface and the approach‐departure clearance surface. It continues outward and
upward at the prescribed slope to an elevation of 87.5 feet above the specified helipad.
It then rises vertically to an elevation of 150 feet above the helipad elevation.
Helicopter Tactical Flight Training Area MCA (Figure 27)
Due to its size, this MCA is not included as part of the Silverbell Army Heliport MCAOD.
The Helicopter Tactical Flight Training Area (TFTA) MCA covers the 3,600‐square mile
TFTA that is used by Silverbell Army Heliport pilots and students. The TFTA is made up of
multiple smaller training areas and allows pilots and students to train for low‐level flights,
including terrain contour and nap of the earth flights, over different types of terrain.
Pinal County Joint Land Use Study
89