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Obstruction Evaluation

  • Aeronautical studies conducted under the provisions of Title 14 CFR, Part 77 (for proposed construction or alteration) or Federal Aviation Act of 1958 (for existing structures)
  • Administered by Air Traffic Division with the coordinated assistance of Flight Procedures Office, Airway Facilities and Airports Divisions
  • Exception: Proposals for structures on airport property are administered by Airports Division with assistance from Flight Procedures Office, Airway Facilities and Air Traffic Divisions

FAR Part 77 Notice Criteria

  • Any proposed construction or alteration more than 200 ft. above ground level (AGL) at its site
  • Within 20,000 ft. of a public-use or military airport having at least one runway more than 3200 ft. in length and exceeding a 100:1 slope
  • Within 10,000 ft. of a public-use or military airport having no runway more than 3200 ft. in length and exceeding a 50:1 slope
  • Within 5,000 ft. of any public-use heliport and exceeding a 25:1 slope
  • Any highway, railroad, or other traverse way for mobile objects of a height which, if adjusted upward to the height of the highest mobile object that would normally traverse it, would exceed the above-mentioned criteria
  • When requested by FAA, any construction or alteration that would be in an instrument approach area and available information indicates it might exceed a FAR Part 77 obstruction standard
  • Any construction or alteration on any public-use or military airport

Processing FAA Form 7460-1

  • Kathy Randolph - Iowa and Kansas
    Brenda Mumper - Missouri and Nebraska
  • An aeronautical study number is assigned and case is entered into OE automation program
  • AT verifies coordinates and site elevation, notifies proponent if any discrepancies found
  • Acknowledgement letter is sent to proponent
  • Flight Procedures, Airway Facilities, Frequency Management, Airports and Military Representatives provide comments to AT
  • If the proposal does not exceed (DNE) notice criteria or obstruction standards, a No Hazard determination is issued with no expiration date, no marking/lighting
  • If proposal exceeds notice criteria, but DNE obstruction standards and is 200 ft. AGL or less, a No Hazard determination is issued, no marking/lighting necessary
  • If proposal exceeds notice criteria, but DNE obstruction standards and is more than 200 ft. AGL, a No Hazard determination is issued with appropriate marking/lighting recommendations

If proposal exceeds obstruction standards and FAA’s preliminary review does not indicate substantial adverse effect, a Determination of Presumed Hazard is issued

  • The proponent may opt to lower the height of the structure so that it DNE obstruction standards; a No Hazard would be issued
  • The proponent may request further study at the original requested height; it is circularized to the public for comments
  • If more than 60 days have elapsed without attempted resolution, a new FAA Form 7460-1 would need to be submitted to reactivate the study

If proposal exceeds obstruction standards and FAA’s preliminary review indicates substantial adverse effect, FAA requests that the proponent lower or move the structure so as to eliminate substantial adverse effect

  • If proponent is able to lower the height and the revised height would not exceed obstruction standards, a No Hazard determination would be issued
  • If proponent is able to lower the height and the revised height would still exceed obstruction standards, the proposal would be circularized for comments
  • If proponent opts to move the structure, a new study would be necessary
  • If the proponent is unable to lower or move the structure, a Determination of Hazard to Air Navigation would be issued

Circularization of proposals

  • Circulars are distributed to the proponent/consultant, county commissioner/mayor of city in which the structure would be located, air traffic control facilities within 60 nautical miles, public-use airport managers within 13 miles and private-use airport managers within 5 miles, and to those who are on AT’s mailing list for circulars; i.e., AOPA, NACO, military representatives, etc.
  • Comments are accepted for a 30-day period, all comments are analyzed for valid aeronautical objections

Issuance of determination

  • If no substantial adverse effect is identified, a No Hazard determination would be issued and supplemental notice would be requested at least 10 days prior to beginning construction and/or within 5 days after structure reaches its greatest height; a survey is requested if required by Flight Procedures Office
  • If structure is found to have substantial adverse effect, a Determination of Hazard to Air Navigation would be issued

Petitions for discretionary review

  • Petition may be filed within 30 days after issuance of the determination
  • Airspace and Rules Division, ATA-400, is focal point for processing petitions
  • Requested review may be granted or denied; if granted, the determination will not be final pending disposition of the petition
  • When review is granted, the regional determination may be affirmed, revised or reversed by FAA Headquarters

FAR Part 77 Obstruction Standards

  • A height more than 500 ft. AGL
  • A height AGL or airport elevation, whichever is greater, exceeding
    • 200 ft. within 3 miles
    • 300 ft. within 4 miles
    • 400 ft. within 5 miles
    • 500 ft. within 6 miles
  • A height that increases a minimum instrument flight altitude within a terminal area (TERPS criteria)
  • A height that increases a minimum obstruction clearance (MOCA) (en route criteria)
  • The surface of a takeoff and landing area of an airport or any imaginary surface established under 77.25, 77.28, or 77.29
    • Civil airport imaginary surfaces (77.25); horizontal, conical, primary, approach, and transitional surfaces
      • A height exceeding a horizontal surface; 150 ft. above airport elevation within a 5,000-ft. or 10,000-ft. radius of a public-use airport
      • A height exceeding a primary surface; length based on runway surface, width based on runway type/most precise approach existing or planned
      • A height exceeding an approach surface; extends outward and upward from each end of primary, applied to each runway end based on type of approach available or planned for that runway end
      • A height exceeding a transitional surface; slopes outward from side of primary and approach surfaces at 7:1, limited to 5,000 ft. either side of approach surface beyond limits of conical surface
      • Airport imaginary surfaces for military airports (77.28); inner horizontal, conical, outer horizontal, primary, clear zone, approach clearance, and transitional surfaces
      • Airport imaginary surfaces for heliports (77.29); primary, approach and transitional surfaces

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