Section 1. General


An aeronautical study must be conducted for all complete notices received.


For ease of use of the OE/AAA automated obstruction programs and correspondence, a separate aeronautical study number must be assigned and a separate obstruction evaluation study must be conducted for:

  1. Each site (location), structure (height), or sponsor.
  1. At times, a single sponsor may file notice for multiple sites. Each site must be assigned a separate aeronautical study number and a separate obstruction evaluation study must be conducted.
  2. At times, a single FAA Form 7460-1 may be received for a single project that covers multiple structures such as an antenna array, windmill clusters, housing development, cluster of buildings, utility poles, or catenaries. Each structure must be assigned a separate aeronautical study number and a separate obstruction evaluation study must be conducted. However, a single determination addressing all of the structures may be issued.
  3. At times, multiple sponsors may be competing for the same FCC license in the same market area and may file notice for the same communications band/frequency/channel using the same effective radiated power at the same location and height. A separate FAA Form 7460-1 should be submitted for each sponsor with information specific to the structure and sponsor. Separate aeronautical study numbers must be assigned and separate obstruction evaluation studies conducted.


A single structure with multiple points of interest, such as a building, may be processed as a single obstruction evaluation study provided that all information including items such as maps, blue prints, elevations, etc., are coordinated with each division for evaluation. In the automated obstruction evaluation case screen, the highest site elevation, or finished floor elevation should be recorded as the site elevation. The tallest point on the structure should be recorded as the above ground elevation, and the closest point of the structure to the closest runway should be recorded as the latitude/longitude. This information would be considered worst case and should be used for recording purposes. For analysis purposes, it may be necessary to use specific information for each point of interest.

  1. Changes to marking/lighting recommendations.
  2. Revisions or corrections to coordinates or elevations after the study has been verified and made available for evaluation by other FAA divisions. This would include revisions or corrections to a notice received from the sponsor; revisions or corrections made necessary by the FAA due to mistakes; revisions or corrections as a result of “as-built" surveys; and revisions or corrections due to receipt of supplemental notice.
  3. Aeronautical studies that supersede previous studies must include a reference to the previous aeronautical study number.
  1. The authorities for conducting aeronautical studies of existing structures is contained in Section 40103, Section 44718, and Part 77. These studies are conducted when deemed necessary by the FAA to determine the physical or electromagnetic effect on the use of the navigable airspace and air navigation facilities. Obstruction evaluation studies may be initiated as a result of:
  1. Information received or a situation observed (e.g., structures reported by flight inspection crews).
  2. A request for a study from another FAA component, another agency, or a person with a valid interest in the matter.
  3. A notice received under the provisions of Part 77 for proposed construction or alteration that has already been started and, therefore, must be considered an existing structure.
  4. A structure blocking all or portions of runways, taxiways, or traffic patterns from being seen from an airport traffic control tower.
  5. Other situations for which such an aeronautical study would be appropriate.
  1. Situations that may require obstruction evaluation of existing structures include, but are not limited to:
  1. Determining the effect of a change in aeronautical procedures.
  2. Determining the effect of a proposed runway construction, extension, or realignment.
  3. Determining the need for providing technical assistance in the design and development of airports.
  4. Determining whether the FAA should recommend that an existing structure be altered or removed.
  5. Determining whether the FAA should recommend that an existing structure be made conspicuous by marking and/or lighting in accordance with current standards.
  6. Determining whether the marking and/or lighting display on an existing structure can be removed or reduced without adversely affecting aviation safety or should be increased to more effectively make its presence known to airmen.
  7. Determining whether an existing structure has an electromagnetic effect upon an air navigation or communications facility, or obstructs the required line of sight from an airport traffic control tower.
  8. Providing recommendations to FCC concerning dismantling abandoned antenna structures.
  9. Providing technical assistance or information to a person, or government organization (Federal, state or local) expressing an interest in the structure and the FAA's responsibility associated with the structure's effect on the safe and efficient use of the navigable airspace.
  1. Conduct an aeronautical study for an existing structure in the same manner as proposed structures except as specifically noted in this order.

A proposal for which construction has already started must be studied as an existing structure. Construction is considered to have started if actual structural work has begun such as the laying of a foundation but not including excavation.


Any proposed structure that would exceed a height of 2,000 feet above ground is presumed to have a substantial adverse effect upon the safe and efficient use of navigable airspace and must be determined to be a hazard to air navigation unless the sponsor, at the time of filing, makes a clear and compelling showing to the contrary.

  1. Notices proposing a structure greater than 2,000 feet in height above the ground that are accompanied with the detailed explanation required in Section 77.7(d) must be processed in the normal manner with one exception. The Obstruction Evaluation Group (OEG) must advise the Rules and Regulations Group when an aeronautical study for a proposed structure exceeding 2,000 feet is being conducted.
  2. Notices received without the detailed explanation must be responded to with a notice stating that the proposed structure is presumed to be a hazard to air navigation and the sponsor has the burden of overcoming this presumption in accordance with Section 77.7(d).
  1. A feasibility study is a limited aeronautical review based on very broad, estimated, or general information supplied for the structure. The study usually addresses only certain issues; e.g., feasibility of height at a general location, feasibility of frequency and power at a general location.
  2. Requests for feasibility studies should be accommodated to the extent existing resources and workloads allow. The need for coordination with other divisions will be based on the type of information supplied for the structure.
  3. A feasibility study must result in a report rather than an official determination.
  4. Feasibility studies will not be accommodated for wind turbine proposals.

While the FAA must maintain a means of contacting parties responsible for filing FAA Form 7460-2, it is not responsible for tracking changes in tower ownership. The FCC antenna structure registration program is specifically intended to register and maintain current files with regards to ownership of antenna structures. Therefore, if the FAA receives ownership changes it must not make those corrections to issued determinations. However, the ownership change should be noted in the automated and/or manual case file. Additionally, request that the sponsor notify the FCC, and, for assurance, forward a copy of the change to the FCC.