6.4 Airport Obstacles Surfaces
Airspace around airports is very essential for safe flight operations. Airports must be sited
in areas where airspace is free from obstruction that could be hazardous to aircraft turning
in the vicinity or on takeoff or approach paths. It is also necessary to prevent the
development and growth of obstructions to airspace that could cause the airport to become
unusable.
According to the provisions outlined in Part 77, an object is an “Obstruction to Air
Navigation” if it is of greater height than any imaginary surface established under the
regulation. These imaginary surfaces either slope out and up from all sides and ends of
runways or are a horizontal plane or a sloping plain above a public-use airport.
There are five imaginary surfaces which the Federal Aviation Administration (FAA) has
applied to public use airports to determine obstructions to air navigation. These airspace
surfaces include the primary, approach, transitional, horizontal, and conical surfaces each
with different standards.
Assumptions:
(a) Aircraft size: Large, to guarantee critical design.(b) Runway Classification: The dimensional standards determined by the runway
classification (visual, non-precision, or precision instrument runways). A
precision instrument runway is fully equipped for instrument landing
procedures with an instrument landing system (ILS) or precision approach radar
(PAR) equipment. Of course, all airports have a period when the conditions
dictate the need for controlling with a precision instrument. So, consider
precision instrument runways.