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Mark Petranchuk
mpetranchuk@cscos.com
(877) CS-SOLVE

Obstruction Studies

FAR Part 77 approach surfaces can be very frustrating for airport managers. C&S prepares obstruction evaluation studies in compliance with FAA regulations to help airports map and identify obstacles within ten feet of penetrating these surfaces. The FAA, in the Code of Federal Regulations, Title 14, FAR Part 77, Objects Affecting Navigable Airspace, has established standards for determining obstructions to navigable airspace, and their effect on the safe and efficient use of airspace. This regulation defines a system of imaginary surfaces around an airport through which no fixed object, structure, or natural vegetation should penetrate.

The imaginary surfaces are designed to protect the critical airspace around an airport and allow for the safe operation of aircraft to and from the airport. These imaginary surfaces are fixed surfaces that do not move. The applicable Part 77 surface dimensions are based on the type of approaches to the airport and are used for aircraft operating under visual flight rules or instrument flight rules.

To identify obstructions to FAR Part 77 surfaces, runways with a non-precision approach use an approach slope of 34:1 up to 10,000 feet. Runways with a precision approach apply an approach slope of 50:1 at a distance of 10,000 feet, with an additional slope of 40:1 for a distance of 40,000 feet. If obstructions are identified using this methodology, the FAA may opt to remove or lower the obstruction, displace the runway threshold, raise visibility minimums, or prohibit specific aircraft operations at the airport in order to mitigate objects and obstructions that penetrate FAR Part 77 surfaces and bring the airport into compliance with this regulation.

In an effort to enhance safety for the flying public, airports will commonly determine what FAR Part 77 surfaces are being penetrated by obstructions and work to remove as many as possible. This doesn't mean that any obstruction to FAR Part 77 makes an airport unsafe; rather it means that having no obstructions to FAR Part 77 makes an airport safer. Many times if an obstruction cannot physically be removed, the FAA will instead allow a red obstruction light to be installed alerting pilots to the obstruction.

C&S assists airport sponsors by providing a recommended course of action for each of the identified obstructions, to be in compliance with FAA requirements.