Vertical Obstruction Military Compatibility Area (Figure 17)
The purpose of the Vertical Obstruction MCA is to regulate the height of all
structures within the area defined by FAA guidance and Air Force AICUZ
instructions with criteria known as “imaginary surfaces” and the Existing
Military Operations Surface (EMOS).
The imaginary surfaces are a 3‐D geographic area comprising approach and
departure airspace corridors and surrounding navigable airspace. 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 mishap.
The Existing Military Operations Surface (EMOS) is airspace unique to Keesler
AFB to support the tactical air training mission at Keesler AFB. Like the
imaginary surfaces, it defines height thresholds for structures in the
navigable airspace and is contained within the imaginary surfaces. The EMOS
is defined as a surface that extends from the thresholds of the runway along
the projection of the centerline, both southwest and northeast for 1 ¾
nautical miles. The EMOS has not been accurately mapped which is
recommended action in the implementation strategies.
Vertical obstructions that can affect flight safety include, but are not limited
to towers, power lines, buildings, and trees. The imaginary surfaces and the
EMOS are explained in more detail in Chapter 3, Keesler AFB Operations in
the Background Report.
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