Chapter 6. Aeronautical Studies
Section 1. General
An obstruction evaluation
study must 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 must be assigned and a separate obstruction evaluation study must be
a. 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.
b. Changes to
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 supplemental notice.
studies that supersede previous studies must include a reference to the previous
aeronautical study number.
6-1-3. STUDY OF EXISTING
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:
received or a situation observed (e.g., structures reported by flight inspection
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
4. A structure blocking all or portions of runways, taxiways, or traffic
patterns from being seen from an airport traffic control tower.
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 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
whether the FAA should recommend that an existing structure be altered or
whether the FAA should recommend that an existing structure be made conspicuous
by marking and/or lighting in accordance with current standards.
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.
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.
recommendations to FCC concerning dismantling abandoned antenna structures.
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.
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 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.
EXCEEDING 2,000 FEET
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.
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) must be
processed in the normal manner with one exception. The Obstruction Evaluation
Group (OEG) must 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.
received without the detailed graphic must 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).
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 must result in a report rather than an official determination.
studies will not be accommodated for wind turbine proposals.
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 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.