The Edges of Airport Airspace Regulations

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The Real Issues Raised by Airport Imaginary Surfaces

Interstices between and among FARs, FSIMS and Drawings

Notice Triggers FAA review

Use in ALP/AMP protects Future

This article in AVIATIONPROS provides some useful insights into the regulation of the airspace which surround airports. The compliance with 14 CFR Part 77 is DEFINED by those regulations, but means of compliance are supplemented, not supplanted by:

FAA Order 8260.3D




Advisory Circulars



TERPS Instruction Letters (TILs)




Yes, indeed Part 77 and TERPS are filled with complex and sometimes seemingly conflicting criteria. And yes, Mr. Castagna the FAA is faced with a Hobbesian choice—deteriorating the margin of safety in the airspace surrounding airports or diminishing the economic development in their neighborhoods.

Two documents, so replete with numbers, oddly create a number of ambiguities in these realms of apparent precision.

For example, TERPS is not part of PART 77.  FAR Part 77 and the Airports GIS Obstruction Surfaces are a sets of identification surfaces which provide obstruction information to the procedure designers. Their purpose is to determine the lowest possible approach/visibility landing minima.

Penetrations to Part 77 or Airport GIS do not mean that the lowest possible minima cannot be achieved.  This depends on where the penetrations are located relative to the runway centerline.

Clearing Part 77 surfaces of penetrations is also tied to grant funding for NPIAS airports.


Similarly, the size of each imaginary surface is based on the category of runway and type of instrument approach available. These surfaces have nothing to do with the visibility minima to the runway ends.  Part 77 surfaces are based on the approach status for each runway– VFR, Non-Precision and Precision.


It is also important to remember that protection of these aerial areas for aircraft movement is not just the responsibility of the FAA. Airports have the ability to develop “Special Instrument Procedures” that only specific aircrews can fly.  This could help ease this burden in some cases.

Smart airport planning includes being aware of future runway developments—adding to their length, improving minima with enhanced navigation systems and adding new runways.  With those potential additions noted, the airport management can address proposals for new structures which could inhibit important aviation growth.






Part 77 and TERPS are vital to the future health of your aviation facility. Taking the time to determine what can and cannot be done, as part of your ALP and AMP processes. Having done so, you have a basis for protecting against potential incursions.  It would be myopic not to include the necessary expertise in these exercises.




David Perry







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