Chapter 6. Aeronautical Studies
Section 1. General
An obstruction evaluation study shall be conducted
for all complete OE notices received.
6-1-2. AERONAUTICAL STUDY NUMBERS
For ease of use of the OE/AAA automated
obstruction programs and correspondence, a separate
aeronautical study number shall be assigned and a
separate obstruction evaluation study shall be
a. Each site (location), structure (height), or
1. At times, a single sponsor may file notice for
multiple sites. Each site shall be assigned a separate
aeronautical study number and a separate obstruction
evaluation study shall 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 shall be assigned
a separate aeronautical study number and a separate
obstruction evaluation study shall 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 shall 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.
b. Changes to marking/lighting recommendations.
c. 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
d. Aeronautical studies that supersede previous
studies shall include a reference to the previous
aeronautical study number.
6-1-3. STUDY OF EXISTING STRUCTURES
a. 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.
b. Situations that may require obstruction evaluation of existing structures include, but are not
1. Determining the effect of a change in
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
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
c. Conduct an aeronautical study for an existing
structure in the same manner as proposed structures
except as specifically noted in this order.
6-1-4. PROPOSALS UNDER
A proposal for which construction has already started
shall 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
6-1-5. STRUCTURES EXCEEDING 2,000
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 shall 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.
a. Notices proposing a structure greater than
2,000 feet in height above the ground that are
accompanied with the detailed graphic required in
Section 77.17(c) shall be processed in the normal
manner with one exception. The Obstruction
Evaluation Group (OEG) shall advise the office of
Airspace Regulations and ATC Procedures Group
when an aeronautical study for a proposed structure
exceeding 2,000 feet is being conducted.
b. Notices received without the detailed graphic
shall be responded to with a determination stating
that the proposed structure is presumed to be,
inherently, a hazard to air navigation and the sponsor
has the burden of overcoming this presumption in
accordance with Section 77.17(c).
6-1-6. FEASIBILITY STUDIES
a. 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.
b. 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.
c. A feasibility study shall result in a report rather
than an official determination.
6-1-7. TOWER OWNERSHIP
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 shall 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.
6-1-8. INFORMAL AIRSPACE MEETINGS
Informal airspace meetings may be held with
interested parties to discuss the obstruction evaluation study and to gather additional facts or
information relevant to the study.