Section 3. Identifying/Evaluating Aeronautical Effect
6-3-1. POLICY
a. The prime objective of the FAA in conducting
OE studies is to ensure the safety of air navigation,
and the efficient utilization of navigable airspace by
aircraft. There are many demands being placed on
the use of the navigable airspace. However, when
conflicts arise concerning a structure being studied,
the FAA emphasizes the need for conserving the
navigable airspace for aircraft; preserving the
integrity of the national airspace system; and
protecting air navigation facilities from either
electromagnetic or physical encroachments that
would preclude normal operation.
b. In the case of such a conflicting demand for the
airspace by a proposed construction or alteration, the
first consideration should be given to altering the
proposal.
c. In the case of an existing structure, first
consideration should be given to adjusting the
aviation procedures to accommodate the structure.
This does not preclude issuing a "Determination Of
Hazard To Air Navigation" on an existing structure
when the needed adjustment of aviation procedures
could not be accomplished without a substantial
adverse effect on aeronautical operations. In all
cases, consideration should be given to all known
plans on file received by the end of the public
comment period or before issuance of a determination if the case was not circularized.
6-3-2. SCOPE
Part 77 establishes standards for determining
obstructions to air navigation. A structure that
exceeds one or more of these standards is presumed
to be a hazard to air navigation unless the obstruction
evaluation study determines otherwise. An obstruction evaluation study shall identify:
a. The effect the proposal would have:
1. On existing and proposed public-use and
military airports and/or aeronautical facilities.
2. On existing and proposed visual flight rule
(VFR)/instrument flight rule (IFR) aeronautical
departure, arrival and en route operations, procedures, and minimum flight altitudes.
3. Regarding physical, electromagnetic, or
line-of-sight interference on existing or proposed air
navigation, communications, radar, and control
systems facilities.
4. On airport capacity, as well as the cumulative
impact resulting from the structure when combined
with the impact of other existing or proposed
structures.
b. Whether marking and/or lighting is necessary.
6-3-3. DETERMINING ADVERSE EFFECT
A structure is considered to have an adverse
aeronautical effect if it first exceeds the obstruction
standards of part 77, and/or is found to have physical
or electromagnetic radiation effect on the operation of
air navigation facilities. A proposed or existing
structure, if not amended, altered, or removed, has an
adverse effect if it would:
a. Require a change to an existing or planned IFR
minimum flight altitude, a published or special
instrument procedure, or an IFR departure procedure
for a public-use airport.
b. Require a VFR operation, to change its regular
flight course or altitude. This does not apply to VFR
military training route (VR) operations conducted
under part 137, or operations conducted under a
waiver or exemption to the CFR.
c. Restrict the clear view of runways, helipads,
taxiways, or traffic patterns from the airport traffic
control tower cab.
d. Derogate airport capacity/efficiency.
e. Affect future VFR and/or IFR operations as
indicated by plans on file.
f. Affect the usable length of an existing or
planned runway.
6-3-4. DETERMINING SIGNIFICANT
VOLUME OF ACTIVITY
The type of activity must be considered in reaching
a decision on the question of what volume of
aeronautical activity is "significant." For example, if
one or more aeronautical operations per day would be
affected, this would indicate regular and continuing
activity, thus a significant volume no matter what the
type of operation. However, an affected instrument
procedure or minimum altitude may need to be used
only an average of once a week to be considered
significant if the procedure is one which serves as the
primary procedure under certain conditions.
6-3-5. SUBSTANTIAL ADVERSE EFFECT
A proposed structure would have, or an existing
structure has, a substantial adverse effect if it causes
electromagnetic interference to the operation of an air
navigation facility or the signal used by aircraft, or if
there is a combination of:
a. Adverse effect as described in paragraph
6-3-3; and
b. A significant volume of aeronautical operations, as described in paragraph
6-3-4, would be
affected.
6-3-6. RESPONSIBILITY
The FAA's obstruction evaluation program transcends organizational lines. In order to determine the
effect of the structure within the required notice
period, each office should forward the results of its
evaluation within 15 working days to the service area
office for further processing. Areas of responsibility
are delegated as follows:
a. Air traffic personnel shall:
1. Identify when the structure exceeds Section
77.23 (a)(1) (see
FIG 6-3-1 thru
FIG 6-3-8) and
apply Section 77.23(b) (see
FIG 5-2-4).
2. Identify the effect on existing and planned
aeronautical operations, air traffic control procedures, and airport traffic patterns and making
recommendations for mitigating adverse effect
including marking and lighting recommendations.
3. Identify when the structure would adversely
affect published helicopter route operations as
specified in paragraph
6-3-8 subparagraph e., of this
order, and forward the case to Flight Standards.
4. Identify whether obstruction marking/lighting are necessary and recommend the
appropriate marking and/or lighting.
5. Identify when negotiations are necessary and
conduct negotiations with the sponsor. This may be
done in conjunction with assistance from other
division/service area office personnel when their
subject expertise is required (e.g., in cases of
electromagnetic interference).
6. Identify when circularization is necessary
and conduct the required circularization process.
7. Evaluate all valid aeronautical comments
received as a result of the circularization and those
received as a result of the division evaluation.
8. Issue the determination (except as noted in
paragraph
7-1-2, subparagraph
b).
b. Regional Airports Division personnel shall:
1. Verify that the airport/runway database has
been reviewed, is correct, and contains all plans on
file pertaining to the OE case.
2. Identify the structure's effect on existing and
planned airports or improvements to airports
concerning airport design criteria including potential
restrictions/impacts on airport operations, capacity,
efficiency and development, and making recommendations for eliminating adverse effect. Airports
Divisions are not required to perform evaluations on
OE cases that are further than 3 NM from the Airport
Reference Point (ARP) of a public-use or military
airport.
3. Determine the effect on the efficient use of
airports and the safety of persons and property on the
ground. Airports will resist structures and activities
that conflict with an airport's planning, design, and/or
recommendations from other divisions/service area
offices.
c. FPO personnel shall:
1. Identify when the structure exceeds Sections
77.23(a)(3), and 77.23(a)(4).
2. Identify the effect upon terminal area IFR
operations, including transitions; radar vectoring;
holding; instrument departure procedures; any
segment of a standard instrument approach procedure
(SIAP) or special SIAP, including proposed
instrument procedures and departure areas; and
making recommendations for eliminating adverse
effect.
NOTE-
This paragraph applies to any IAP and Special SIAP at
public-use and private-use airports.
3. Identify the effect on minimum en route
altitudes (MEA); minimum obstruction clearance
altitudes (MOCA); minimum vectoring altitudes
(MVA); minimum IFR altitudes (MIA); minimum
safe altitudes (MSA); minimum crossing altitudes
(MCA); minimum holding altitudes (MHA); turning
areas and termination areas; and making recommendations for eliminating adverse effect.
4. Coordinate with air traffic and technical
operations services personnel to determine the effect
of any interference with an air navigation facility on
any terminal or en route procedure.
5. State what adjustments can be made to the
procedure/structure to mitigate or eliminate any
adverse effects of the structure on an instrument flight
procedure.
d. Regional Flight Standards personnel shall
identify the effect on fixed-wing and helicopter VFR
routes, terminal operations, and other concentrations
of VFR traffic. When requested by air traffic, the
Flight Standards Division shall also evaluate the
mitigation of adverse effect on VFR operations for
marking and/or lighting of structures.
e. Technical Operations Services personnel shall
identify any electromagnetic and/or physical effect
on air navigation and communications facilities
including:
1. The presence of any electromagnetic effect in
the frequency protected service volume of the
facilities shown in
FIG 6-3-18,
FIG 6-3-19, and
FIG 6-3-20.
2. The effect on the availability or quality of
navigational or communications signals to or from
aircraft including lighting systems (e.g., VGSI), and
making recommendations to eliminate adverse
effect.
3. The effect on ground-based communications
and NAVAID equipment, and the signal paths
between ground-based and airborne equipment, and
making recommendations to eliminate adverse
effect.
4. The effect on the availability or quality of
ground-based primary and secondary radar;
direction finders; and air traffic control tower
line-of-sight visibility; and making recommendations to eliminate adverse effect.
5. The effect of sunlight or artificial light
reflections, and making recommendations to eliminate adverse effect.
f. Military personnel are responsible for evaluating the effect on airspace and routes used by the
military.
g. Other applicable FAA offices or services may
be requested to provide an evaluation of the structure
on a case-by-case basis.
FIG 6-3-2
NEAR AIRPORTS
FIG 6-3-3
CIVILIAN AIRPORT IMAGINARY SURFACES
Isometric View of Section A A
FIG 6-3-4
MILITARY AIRPORT IMAGINARY SURFACES
FIG 6-3-5
MILITARY AIRPORT IMAGINARY SURFACES
FIG 6-3-6
MILITARY AIRPORT IMAGINARY SURFACES
FIG 6-3-7
CLEAR ZONE - MILITARY
FIG 6-3-8
AIRPORT IMAGINARY SURFACES FOR HELIPORTS
FIG 6-3-9
PART 77, APPROACH SURFACE DATA
6-3-7. AIRPORT SURFACES AND
CLEARANCE AREAS
a. CIVIL AIRPORT SURFACES
1. Civil airport imaginary surfaces are defined
in Section 77.25 and are based on the category of each
runway according to the type of approach (visual,
nonprecision, or precision) available or planned for
each runway end (see
FIG 6-3-3). The appropriate
runway imaginary surface shall be applied to the
primary surfaces related to the physical end of the
specific runway surface that is usable for either
takeoff or landing.
2. Approach Surface Elevation - Use the
runway centerline elevation at the runway threshold
and the elevation of the helipad as the elevation from
which the approach surface begins (see Sections
77.25 and 77.29).
3. Heliport imaginary surfaces are defined in
Section 77.29 and are based upon the size of the
takeoff and landing area.
4. Planned Airport/Runway Improvements -
Consider the planned runway threshold and approach
type when there is a plan on file with the FAA or with
an appropriate military service to extend the runway
and/or upgrade its use or type of approach. The
existing runway threshold and type of approach may
be used for temporary structures/equipment, as
appropriate.
b. MILITARY AIRPORT SURFACES - The
obstruction standards in Section 77.25, Civil Airport
Imaginary Surfaces, apply to civil operated joint-use
airports. The obstruction standards in Section 77.28,
Military Airport Imaginary Surfaces, are applicable
only to airports operated and controlled by a military
service of the United States, regardless of whether use
by civil aircraft is permitted.
c. TERMINAL OBSTACLE CLEARANCE
AREA - The terminal obstacle clearance area
specified in Section 77.23(a)(3) includes the initial,
intermediate, final, and missed approach segments of
an instrument approach procedure, and the circling
approach and instrument departure areas. The
applicable FAA approach and departure design
criteria are contained in the 8260.3 Order series.
d. EN ROUTE OBSTACLE CLEARANCE
AREA - The en route obstacle clearance area
specified in Section 77.23(a)(4) is applicable when
evaluating the effect of a structure on an airway, a
feeder route, and/or an approved off-airway route
(direct route) as prescribed in the 8260.3 Order series.
6-3-8. EVALUATING EFFECT ON VFR
OPERATIONS
a. PURPOSE. These guidelines are for use in
determining the effect of structures, whether
proposed or existing, upon VFR aeronautical
operations in the navigable airspace. The intent of
these guidelines is to provide a basis for analytical
judgments in evaluating the effect of proposals on
VFR operations.
b. CONSIDERATIONS
1. Minimum VFR Flight Altitudes. Minimum
VFR flight altitudes are prescribed by regulation.
Generally speaking, from a VFR standpoint, the
navigable airspace includes all airspace 500 feet AGL
or greater and that airspace below 500 feet required
for:
(a) Takeoff and landing, including the airport
traffic pattern.
(b) Flight over open water and sparsely
populated areas (an aircraft may not be operated
closer than 500 feet to any person, vessel, vehicle, or
structure).
(c) Helicopter operations when the operation
may be conducted without hazard to persons and
property on the surface.
2. VFR Weather Minimums. Proposed or
existing structures potentially have the greatest
impact in those areas where VFR operations are
conducted when ceiling and/or visibility conditions
are at or near VFR weather minimums. Any structure
that would interfere with a significant volume of low
altitude flights by actually excluding or restricting
VFR operations in a specific area would have a
substantial adverse effect and may be considered a
hazard to air navigation.
3. Marking and/or Lighting of Structures. Not
every structure penetrating the navigable airspace is
considered to be a hazard to air navigation. Some may
be marked and/or lighted so pilots can visually
observe and avoid the structures.
4. Shielded Structures. A structure may be
"shielded" by being located in proximity to other
permanent structures or terrain and would not, by
itself, adversely affect aeronautical operations (see
paragraph
6-3-13).
5. Height Of Structures. Structures are of
concern to pilots during a climb after takeoff, low
altitude operations, and when descending to land.
Any structure greater than 500 feet AGL, or
structures of any height which would affect landing
and takeoff operations, requires extensive evaluation
to determine the extent of adverse effect on VFR
aeronautical operations.
6. Airport Traffic Patterns. The primary concern
regarding structures in airport traffic pattern areas is
whether they would create a dangerous situation
during a critical phase of flight.
7. Class B and C Airspace. Structures that
exceed obstruction standards in areas available for
VFR flight below the floor of Class B or C airspace
areas require careful evaluation. Class B and C
airspace areas are designed to provide a more
regulated environment for IFR and VFR traffic in and
around certain airports. Consequently, the floors of
some Class B and C areas compress VFR operations
into airspace of limited size and minimum altitude
availability.
8. VFR Routes. Pilots operating VFR frequently fly routes that follow rivers, coastlines,
mountain passes, valleys, and similar types of natural
landmarks or major highways, railroads, powerlines,
canals, and other manmade structures. A VFR route
may also be comprised of specific radials of a Very
High Frequency Omnidirectional Range (VOR).
These routes may correspond to an established
Federal Airway, direct radials between navigation
facilities, or a single radial providing transition to a
route predicated on visual aids. While there may be
established minimum en route altitudes for segments
of these routes and navigation is dependent upon
adequate signal reception, a VFR pilot may fly at an
altitude below the established minimum altitude in
order to maintain visual contact with the ground. The
basic consideration in evaluating the effect of
obstructions on operations along these routes is
whether pilots would be able to visually observe and
avoid them during marginal VFR weather conditions.
At least 1-mile flight visibility is required for VFR
operations beneath the floor of controlled airspace.
This means that a surface reference used for VFR low
altitude flight must be horizontally visible to pilots
for a minimum of 1 mile.
c. EN ROUTE OPERATIONS. The area considered for en route VFR flight begins and ends
outside the airport traffic pattern airspace area or
Class B, C, and D airspace areas.
1. A structure would have an adverse effect
upon VFR air navigation if its height is greater than
500 feet above the surface at its site, and within 2
statute miles of any regularly used VFR route (see
FIG 6-3-10).
2. Evaluation of obstructions located within
VFR routes must recognize that pilots may, and
sometimes do, operate below the floor of controlled
airspace during low ceilings and 1-mile flight
visibility. When operating in these weather conditions and using pilotage navigation, these flights
must remain within 1 mile of the identifiable
landmark to maintain visual reference. Even if made
more conspicuous by the installation of high intensity
white obstruction lights, a structure placed in this
location could be a hazard to air navigation because
after sighting it, the pilot may not have the
opportunity to safely circumnavigate or overfly the
structure.
3. VFR MILITARY TRAINING ROUTES
(VR) - Operations on VRs provide military aircrews
low altitude, high speed navigation and tactics
training, and are a basic requirement for combat
readiness (see FAAO JO 7610.4, Special Operations). Surface structures have their greatest impact
on VFR operations when ceiling and visibility
conditions are at or near basic VFR minimums.
Accordingly, the guidelines for a finding of
substantial adverse effect on en route VFR operations
are based on consideration for those operations
conducted under part 91 that permits flight clear of
clouds with 1 mile flight visibility outside controlled
airspace. In contrast, flight along VRs can be
conducted only when weather conditions equal or
exceed 3,000 feet ceiling and 5 miles visibility. A
proposed structure's location on a VR is not a basis
for determining it to be a hazard to air navigation;
however, in recognition of the military's requirement
to conduct low altitude training, disseminate part 77
notices and aeronautical study information to
military representatives. Additionally, attempt to
persuade the sponsor to lower or relocate a proposed
structure that exceeds obstruction standards and has
been identified by the military as detrimental to its
training requirement.
d. AIRPORT AREAS - Consider the following
when determining the effect of structures on VFR
operations near airports:
1. Traffic Pattern Airspace - There are many
variables that influence the establishment of airport
arrival and departure traffic flows. Structures in the
traffic pattern airspace may adversely affect air
navigation by being a physical obstruction to air
navigation or by distracting a pilot's attention during
a critical phase of flight. The categories of aircraft
using the airport determine airport traffic pattern
airspace dimensions.
(a) Traffic Pattern Airspace dimensions (See
FIG 6-3-11).
(b) Within Traffic Pattern Airspace - A
structure that exceeds a 14 CFR, part 77 obstruction
standard and that exceeds any of the following
heights is considered to have an adverse effect and
would have a substantial adverse effect if a significant
volume of VFR aeronautical operations are affected
except as noted in paragraph
6-3-8
d.1.(c) and
(d)
(see
FIG 6-3-12).
(c) The height of the transition surface (other
than abeam the runway), the approach slope (up to the
height of the horizontal surface), the horizontal
surface, and the conical surface (as applied to visual
approach runways, Section 77.25).
(d) Beyond the lateral limits of the conical
surface and in the climb/descent area - 350 feet above
airport elevation or the height of 14 CFR Section
77.23a.(2), whichever is greater not to exceed 500
feet above ground level (AGL). The climb/descent
area begins abeam the runway threshold being used
and is the area where the pilot is either descending to
land on the runway or climbing to pattern altitude
after departure. (The area extending outward from a
line perpendicular to the runway at the threshold, see
FIG 6-3-13).
(e) Beyond the lateral limits of the conical
surface and not in the climb/descent area of any
runway - 500 feet above airport elevation (AE) not to
exceed 500 feet AGL.
(f) An existing structure (that has been
previously studied by the FAA), terrain, or a
proposed structure (that would be shielded by
existing structures) may not be considered to have a
substantial adverse effect. In such instances, the
traffic pattern may be adjusted as needed on a
case-by-case basis.
(g) Exceptions may be made on a case-by-case basis when the surrounding terrain is
significantly higher than the airport elevation, the
established traffic pattern altitude is less than 800 feet
above airport elevation or "density altitude" is a
consideration.
2. Terminal Transition Routes - A structure
would have an adverse effect upon VFR air
navigation if it:
(a) Exceeds a height of 500 feet above the
surface at its site; and
(b) Is located within 2 statute miles of the
centerline of any regularly used VFR route (see
FIG 6-3-10).
3. VFR Approach Surface Slope Ratios - A
structure would have an adverse effect upon VFR air
navigation if it penetrates the approach surface slope
of any runway. The following slope ratios are applied
to the end of the primary surface:
(a) 20:1 for civil visual approaches.
(b) 50:1 for military runway approaches.
(c) 8:1 for civil helicopter approaches
surfaces.
(d) 10:1 for military helicopter approach
surfaces.
FIG 6-3-11
TRAFFIC PATTERN AIRSPACE
FIG 6-3-12
TRAFFIC PATTERN AIRSPACE ADVERSE EFFECT
FIG 6-3-13
TRAFFIC PATTERN AIRSPACE CLIMB/DESCENT AREAS
e. HELICOPTERS - The special maneuvering
characteristics of helicopters are recognized in
Sections 91.119 and 91.155, provided operations are
conducted without hazard to persons or property on
the ground. Helicopter pilots must also operate at a
speed that will allow them to see and avoid
obstructions. Consequently, proposed or existing
structures are not considered factors in determining
adverse effect upon helicopter VFR operations
except as follows:
1. En route. When the Administrator prescribes
routes and altitudes for helicopters, the exemptions to
part 91 for helicopters do not apply. Thus, any
structure would have an adverse effect if it penetrates
an imaginary surface 300 feet below an established
helicopter minimum flight altitude and is located
within 250 feet either side of the established route's
centerline.
2. Heliport Landing/Takeoff Area. Any structure would have an adverse effect if it would exceed
any of the heliport imaginary surfaces. Although
helicopter approach-departure paths may curve, the
length of the approach-departure surface remains
fixed.
f. AGRICULTURAL AND INSPECTION
AIRCRAFT OPERATIONS - Rules that apply to
agricultural dispensing operations, as prescribed in
part 137, allow deviation from part 91 altitude
restrictions. It is the pilot's responsibility to avoid
obstacles because the agricultural operations must be
conducted without creating a hazard to persons or
property on the surface. Similar operations include
pipeline, power line, and military low-level route
inspections. Consequently, these operations are not
considered in reaching a determination of substantial
adverse effect.
NOTE-
Before and after the dispensing is completed, the pilot is
required to operate under the part 91 minimum altitudes.
g. OPERATIONS UNDER WAIVER OR
EXEMPTION TO CFR - Waivers and/or exemptions
to CFR operating rules include provisions to ensure
achievement of a level of safety equivalent to that
which would be present when complying with the
regulation waived or exempted. Additionally,
waivers and exemptions do not relieve pilots of their
responsibility to conduct operations without creating
a hazard to persons and property on the surface.
Accordingly, a determination of hazard to air
navigation shall not be based upon a structure's effect
on aeronautical operations conducted under a waiver
or exemption to CFR operating rules.
6-3-9. EVALUATING EFFECT ON IFR
OPERATIONS
a. PURPOSE. This section provides general
guidelines for determining the effect of structures,
whether proposed or existing, upon IFR aeronautical
operations.
b. STANDARDS. Obstruction standards are used
to identify potential adverse effects and are not the
basis for a determination. The criteria used in
determining the extent of adverse affect are those
established by the FAA to satisfy operational,
procedural, and electromagnetic requirements. These
criteria are contained in regulations, advisory
circulars, and orders (e.g., the 8260 Order series and
Order 7110.65). Obstruction evaluation personnel
shall apply these criteria in evaluating the extent of
adverse effect to determine if the structure being
studied would actually have a substantial adverse
effect and would constitute a hazard to air navigation.
c. IFR MINIMUM FLIGHT ALTITUDES. Technical Operations Aviation System Standards is the
principal FAA element responsible for establishing
instrument procedures and minimum altitudes for
IFR operations. FPO personnel shall evaluate the
effect of proposed structures on IFR aeronautical
operations as outlined in Order 8260.19, Flight
Procedures and Airspace.
d. EN ROUTE IFR OPERATIONS
1. Minimum En Route Altitudes (MEA). MEAs
are established for each segment of an airway or an
approved route based upon obstacle clearance,
navigational signal reception, and communications.
The MEA assures obstruction clearance and
acceptable navigational signal coverage over the
entire airway or route segment flown. Any structure
that will require an MEA to be raised has an adverse
effect. Careful analysis by the appropriate Flight
Procedures and air traffic personnel is necessary to
determine if there would be a substantial adverse
effect on the navigable airspace. Generally, the loss
of a cardinal altitude is considered a substantial
adverse effect. However, the effect may not be
substantial if the aeronautical study discloses that the
affected MEA is not normally flown by aircraft, nor
used for air traffic control purposes.
2. Minimum Obstruction Clearance Altitudes
(MOCA). MOCAs assure obstacle clearance over the
entire route segment to which they apply and assure
navigational signal coverage within 22 NM of the
associated VOR navigational facility. For that
portion of the route segment beyond 22 NM from the
VOR, where the MOCA is lower than the MEA and
there are no plans to lower the MEA to the MOCA,
a structure that affects only the MOCA would not be
considered to have substantial adverse effect. Other
situations require study as ATC may assign altitudes
down to the MOCA under certain conditions.
3. Minimum IFR Altitudes (MIA). These
altitudes are established in accordance with Order
7210.37, En Route Minimum IFR Altitude Sector
Charts, to provide the controller with minimum IFR
altitude information for off-airway operations. MIAs
provide the minimum obstacle clearance and are
established without respect to flight-checked radar or
normal radar coverage. Any structure that would
cause an increase in a MIA is an obstruction, and
further study is required to determine the extent of
adverse effect. Radar coverage adequate to vector
around such a structure is not, of itself, sufficient to
mitigate a finding of substantial adverse effect that
would otherwise be the basis for a determination of
hazard to air navigation.
4. IFR Military Training Routes (IR's) -
Operations on IR's provide pilots with training for
low altitude navigation and tactics (see FAAO JO
7610.4, Special Operations). Flight along these
routes can be conducted below the minimum IFR
altitude specified in part 91, and the military conducts
operational flight evaluations of each route to ensure
compatibility with their obstructions clearance
requirements. A proposed structure's location on an
IR is not a basis for determining it to be a hazard to
air navigation; however, in recognition of the
military's requirement to conduct low altitude
training, disseminate part 77 notices and aeronautical
study information to military representatives.
Additionally, attempt to persuade the sponsor to
lower, or relocate proposed structures that exceed
obstruction standards and have been identified by the
military as detrimental to their training requirement.
5. Radar Bomb Sites (RBS) - These sites are a
vital link in the low level training network used by the
U.S. Air Force to evaluate bomber crew proficiency.
They provide accurate radar records for aircraft flying
at low altitudes attacking simulated targets along the
RBS scoring line. An obstruction located within the
flights' RBS boundaries may have a substantial
adverse effect and a serious operational impact on
military training capability.
e. TERMINAL AREA IFR OPERATIONS. The
obstruction standards contained in part 77 are also
used to identify obstructions within terminal obstacle
clearance areas. Any structure identified as an
obstruction is considered to have an adverse effect;
however, there is no clear-cut formula to determine
what extent of adverse effect is considered
substantial. Instrument approach and departure
procedures are established in accordance with
published obstacle clearance guidelines and criteria.
However, there are segments of instrument approach
procedures where the minimum altitudes may be
revised without substantially effecting landing
minimums. Thus, the determination must represent a
decision based on the best facts that can be obtained
during the aeronautical study.
1. Instrument Approach Procedures
(IAP)/Special SIAP. Flight Procedures personnel are
responsible for evaluating the effect of structures
upon any segment of an IAP/Special SIAP, any
proposed IAP/Special SIAP, or any departure
restriction. However, all FAA personnel involved in
the obstruction evaluation process should be familiar
with all aspects of the terminal area IFR operations
being considered. If Flight Procedures personnel
determine that a structure will affect instrument flight
procedures, their evaluation should include those
procedural adjustments that can be made without
adversely affecting IFR operations. When the study
discloses that procedural adjustments to reduce or
mitigate any adverse effect cannot be accomplished,
then the comments to air traffic shall identify the
significance of this effect on procedures and
aeronautical operations.
NOTE-
This paragraph applies to any IAP and Special SIAP at
public-use and private-use airports.
2. Minimum Vectoring Altitudes (MVA). These
altitudes are based upon obstruction clearance
requirements only (see Order 8260.19). The area
considered for obstacle clearance is the normal
operational use of the radar without regard to the
flight-checked radar coverage. It is the responsibility
of individual controllers to determine that a target
return is adequate for radar control purposes. MVAs
are developed by terminal facilities, approved by the
National Flight Procedures Office and published for
controllers on MVA Sector Charts. Any structure that
would cause an increase in an MVA is an obstruction
and a study is required to determine the extent of
adverse effect. Radar coverage adequate to vector
around such a structure is not, of itself, sufficient to
mitigate a finding of substantial adverse effect that
would otherwise be the basis for a determination of
hazard to air navigation.
3. Military Airports. With the exception of the
U.S. Army, the appropriate military commands
establish and approve terminal instrument procedures for airports under their respective jurisdictions.
Consequently, the OES shall ensure that the military
organizations are provided the opportunity to
evaluate a structure that may affect their operations.
While the military has the responsibility for
determining the effect of a structure, it is expected
that the FPO will assist air traffic in reconciling
differences in the military findings.
4. Departure Procedures. TERPS, Chapter 12,
Civil Utilization of Area Navigation (RNAV)
Departure Procedures, contains criteria for the
development of IFR departure procedures. An
obstacle that penetrates the 40:1 departure slope is
considered to be an obstruction to air navigation.
Further study is required to determine if adverse
effect exists. Any proposed obstacle that penetrates
the 40:1 departure slope, originating at the departure
end of runway (DER) by up to 35 feet will be
circularized. If an obstacle penetrates the 40:1
departure slope by more than 35 feet, it is presumed
to be a hazard, and a Notice of Presumed Hazard will
be issued, and processed accordingly. Analysis by the
National Flight Procedures Office and air traffic
personnel is necessary to determine if there would be
a substantial adverse effect on the navigable airspace.
5. Minimum Safe Altitudes (MSA). A MSA is
the minimum obstacle clearance altitude for
emergency use within a specified distance from the
navigation facility upon which a procedure is
predicated. These are either Minimum Sector
Altitudes, established for all procedures within a
25-mile radius of the navigational facility (may be
increased to 30 miles under certain conditions), or
Emergency Safe Altitudes, established within a
100-mile radius of the navigation facility and
normally used only in military procedures at the
option of the approval authority. These altitudes are
designed for emergency use only and are not
routinely used by pilots or by air traffic control.
Consequently, they are not considered a factor in
determining the extent of adverse effect, used as the
basis of a determination, or addressed in the public
notice of an aeronautical study.
f. CONSIDERING ACCURACY. Experience has
shown that submissions often contain elevation
and/or location errors. For this reason, Flight
Procedures uses vertical and horizontal accuracy
adjustments, as reflected below, to determine the
effect on IFR operations.
1. Accuracy Application - Current directives
require the FPO to apply accuracy standards to
obstacles when evaluating effects on instrument
procedures. These accuracy standards typically
require an adjustment of 50 feet vertically and 250
feet horizontally to be applied in the most critical
direction. Normally, these adjustments are applied to
those structures that may become the controlling
obstructions and are applicable until their elevation
and location are verified by survey.
2. Certified Accuracy - The FPO shall notify air
traffic whenever certified accuracy is needed to
determine if the structure will have an adverse effect.
Air traffic shall then contact the sponsor to request a
surveyed verification of the elevation and location.
The acceptable accuracy verification method must be
provided and certified by a licensed engineer or
surveyor. The survey must include the plus or minus
accuracy required by the FPO, as well as the signature
of the engineer/surveyor and the appropriate seal.
3. Determination - A final determination based
on improved accuracy shall not be issued until after
the certified survey is received and evaluated.
4. Survey Information Distribution - When the
certified survey is received, Air Traffic personnel
shall ensure that the survey information is provided
to FPO personnel and shall send to NACO a copy of
the survey attached to the FAA form 7460-2, Notice
of Actual Construction or Alteration.
6-3-10. EVALUATING EFFECT ON AIR
NAVIGATION AND COMMUNICATION
FACILITIES
a. The FAA is authorized to establish, operate, and
maintain air navigation and communications facilities and to protect such facilities from interference.
During evaluation of structures, factors that may
adversely affect any portion or component of the
NAS must be considered. Since an electromagnetic
interference potential may create adverse effects as
serious as those caused by a physical penetration of
the airspace by a structure, those effects shall be
identified and stated. Proposals will be handled,
when appropriate, directly with FCC through
Spectrum Assignment and Engineering Services.
b. Technical operations services personnel shall
evaluate notices to determine if the structure will
affect the performance of existing or proposed NAS
facilities. The study must also include any plans for
future facilities, proposed airports, or improvements
to existing airports.
c. The physical presence of a structure and/or the
electromagnetic signals emanating or reflecting there
from may have a substantial adverse effect on the
availability, or quality of navigational and communications signals, or on air traffic services needed for
the safe operation of aircraft. The following general
guidelines are provided to assist in determining the
anticipated interference.
1. Instrument Landing System (ILS) - Transmitting antennas are potential sources of
electromagnetic interference that may effect the
operation of aircraft using an ILS facility. The
antenna height, radiation pattern, operating frequency, effective radiated power (ERP), and its
proximity to the runway centerline are all factors
contributing to the possibility of interference.
Normally, any structure supporting a transmitting
antenna within the established localizer and/or
glide-slope service volume area must be studied
carefully. However, extremes in structure height,
ERP, frequency, and/or antenna radiation pattern may
require careful study of structures up to 30 NM from
the ILS frequency's protected service volume area.
(a) ILS Localizer. Large mass structures
adjacent to the localizer course and/or antenna
array are potential sources of reflections and/or
re-radiation that may affect facility operation. The
shape and intensity of such reflections and/or
re-radiation depends upon the size of the reflecting
surface and distance from the localizer antenna. The
angle of incidence reflection in the azimuth plane
generally follows the rules of basic optical reflection.
Normally, in order to affect the course, the reflections
must come from structures that lie in or near the
on-course signal. Large mass structures of any
type, including metallic fences or powerlines,
within plus/minus 15 degrees of extended centerline
up to 1 NM from the approach end of the runway and
any obstruction within 500 feet of the localizer
antenna array must be studied carefully. (Refer to
FAAO JO 6750.16, Siting Criteria for Instrument
Landing Systems).
(b) ILS Glide Slope. Vertical surfaces within
approximately 1,000 feet of the runway centerline
and located up to 3,000 feet forward of the glide slope
antenna can cause harmful reflections. Most
interference to the glide slope are caused by
discontinuities in the ground surface, described
approximately as a rectangular area 1,000 feet wide
by 5,000 feet long, extending forward from the glide
slope antenna and centered at about the runway
centerline. Discontinuities are usually in the form
of rough terrain or buildings (refer to FAAO
JO 6750.16, Siting Criteria for Instrument Landing
Systems).
2. Microwave Landing System (MLS). The
guidelines stated for ILS systems above also apply to
MLS installations. The established MLS service
volume defines the area of concern.
3. Very High Frequency Omni-Directional
Radio Range and Tactical Air Navigation Aid
(VOR/TACAN). Usually, there should be no
reflecting structures or heavy vegetation (trees,
brush, etc.) within a 1,000 foot radius of the VOR or
the TACAN antenna. Interference may occur from
large structures or powerlines up to 2 NM from the
antenna. (Refer to FAAO 6820.10, VOR, VOR/DME, and TACAN Siting Criteria).
4. Air Route Surveillance Radar/Airport Surveillance Radar (ARSR/ASR). Normally, there
should be no reflecting structures within a 1,500-foot
radius of the radar antenna. In addition, large
reflective structures up to 3 NM from the antenna can
cause interference unless they are in the "shadow" of
topographic features.
5. Air Traffic Control Radar Beacon (ATCRB).
The effects encountered due to reflections of the
secondary radar main lobe are more serious than
those associated with primary radar. Therefore, it is
necessary to ensure that no large vertical reflecting
surface penetrates a 1,500-foot radius horizontal
plane located 25 feet below the antenna platform. In
addition, interference may occur from large
structures up to 12 miles away from the antenna. This
distance will depend on the area of the reflecting
surface, the reflection coefficient of the surface,
and its elevation with respect to the interrogator
antenna. (Refer to FAAO 6310.6, Primary/Secondary Terminal Radar Siting Handbook).
6. Directional Finder (DF). The DF antenna site
should be free of structures that will obstruct
line-of-sight with aircraft at low altitudes. The
vicinity within 300 feet of the antenna should be free
of metallic structures which can act as re-radiators.
7. Communication Facilities. Minimum desirable distances to prevent interference problems
between communication facilities and other
construction are:
(a) 1,000 feet from power transmission lines
(other than those serving the facility) and other radio
or radar facilities.
(b) 300 feet from areas of high vehicle
activity such as highways, busy roads, and large
parking areas.
(c) One (1) NM from commercial broadcasting stations (e.g., FM, TV).
8. Approach Lighting System. No structure,
except the localizer antenna, the localizer far field
monitor antenna, or the marker antenna shall protrude
above the approach light plane. For approach light
plane clearance purposes, all roads, highways,
vehicle parking areas, and railroads shall be
considered as vertical solid structures. The clearance
required above interstate highways is 17 feet; above
railroads, 23 feet; and for all other public roads,
highways, and vehicle parking areas, 15 feet. The
clearance required for a private road is 10 feet or the
highest mobile structure that would normally use the
road, which would exceed 10 feet. The clearance for
roads and highways shall be measured from the
crown of the road; the clearance for railroads shall be
measured from the top of the rails. For vehicle
parking areas, clearance shall be measured from the
average grade in the vicinity of the highest point.
Relative to airport service roads substantial adverse
effect can be eliminated if all vehicular traffic is
controlled or managed by the air traffic control
facility. A clear line-of-sight is required to all lights
in the system from any point on a surface, one-half
degree below the aircraft descent path and extending
250 feet each side of the runway centerline, up to
1,600 feet in advance of the outermost light in the
system. The effect of parked or taxiing aircraft shall
also be considered when evaluating line-of-sight for
approach lighting systems.
9. Visual Approach Slope Indicator
(VASI)/Precision Approach Path Indicator (PAPI).
No structures or obstructions shall be placed within
the clearance zone for the particular site involved or
the projected visual glide path.
NOTE-
VASI and PAPA now fall under the heading of VGSI.
10. Runway End Identifier Lights (REIL). No
structures or obstructions shall be placed within the
established clearance zone.
d. Factors that modify the evaluation criteria
guidelines require consideration. Some facility
signal areas are more susceptible to interference than
others. The operational status of some signals may
already be marginal because of existing interference
from other structures. In addition, the following
characteristics of structures must be considered:
1. The higher the structure's height is in relation
to the antenna, the greater the chance of interfering
reflections. Any structure subtending a vertical angle
greater than one degree from the facility is usually
cause for concern. Tall structures, such as radio
towers and grain elevators, can interfere from
distances greater than those listed in the general
criteria.
2. The type of construction material on the
reflecting surface of the structure is a factor, with
nonmetallic surfaces being less troublesome than
metallic or metallic impregnated glass.
3. Aircraft hangars with large doors can be a
special problem because the reflecting surface of the
hangar varies appreciably with changes in the
position of the doors.
4. Interference is usually caused by mirror
reflections from surfaces on the structure. Orientation
of the structure therefore plays an important part in
the extent of the interference. Reflections of the
largest amplitude will come from signals striking a
surface perpendicular to the signals. Signals striking
a surface at a shallow angle will have a smaller
amplitude.
e. Air traffic personnel shall request technical
operations services personnel to assist them in
discussions with sponsors to explore alternatives to
resolve the prospective adverse effects to facilities.
These may involve design revisions, relocation, or
reorientation depending on the character of the
construction and facility involved.
f. Attempt to resolve electromagnetic interference
(EMI) before issuing a hazard determination. Notify
the sponsor by letter (automated DPH letter) that the
structure may create harmful EMI and include in the
letter the formula and values that were applied, the
specific adverse effects expected, and an offer to
consider alternatives. Provide the sponsor, as well as
the FAA, ample time to exhaust all available avenues
for positive resolution. The intent of this process is to
allow the sponsor adequate time to consider the
problems and the alternatives before a decision is
rendered by the issuance of the FAA determination.
Follow these guidelines in all situations where
harmful EMI is projected by the study.
6-3-11. EVALUATING PLANNED OR
FUTURE AIRPORT DEVELOPMENT
PROGRAMS
The national system of airports consists of public,
civil, and joint-use airport facilities considered
necessary to adequately meet the anticipated needs of
civil aeronautics. Airport Planning and Programming
Offices are the most accurate sources of up-to-date
information on airport development plans. Consequently, Airports personnel are expected to
extensively review structures in reference to the safe
and orderly development of airport facilities,
including what development will realistically be
accomplished within a reasonable time. Areas of
consideration in accomplishing this responsibility
are:
a. Future Development of Existing Airports. A
detailed review in this area requires looking at current
planned airport projects, national airport plan data,
and land-use planning studies in the vicinity of the
structure. The results of the study forwarded to air
traffic shall include appropriate comments regarding
the extent of Federal aid, sponsor airport investments,
the airport owner's obligations in existing grant-in-aid agreements, and anticipated aeronautical activity
at the airport and in the general area. If a structure
would adversely impact an airport's efficiency,
utility, or capacity, the responsible Airports Office
should document this impact in its evaluation.
Comments should include recommended new
location(s) for the structure as appropriate.
b. New Airport Development. When a structure
requiring notice under part 77 and any new airport
development are both in the same vicinity, Airports
personnel shall study the interrelationship of the
structure and the airport. Additionally, supplemental
information on the proposed airport site shall be
furnished to air traffic. If a substantial adverse effect
is anticipated, Airports personnel shall provide
detailed comments and specific recommendations for
mitigating the adverse effects.
6-3-12. EVALUATING TEMPORARY
CONSTRUCTION
a. Temporary Construction Equipment. Construction of structures normally requires use of temporary
construction equipment that is of a greater height than
the proposed structure. Appropriate action is
necessary to ensure that the temporary construction
equipment does not present a hazard to air navigation.
It is not possible to set forth criteria applicable to
every situation; however, the following action
examples may help to minimize potential problems:
1. If use of the temporary construction
equipment is on an airport, it may be necessary to
negotiate with airport managers/owners to close a
runway, taxiway, temporarily move a runway
threshold, or take other similar action.
2. Negotiate with equipment operators to raise
and lower cranes, derricks, or other construction
equipment when weather conditions go below
predetermined minimums as necessary for air traffic
operations or as appropriate for the airport runways
in use.
3. Control the movement of construction
vehicle traffic on airports.
4. Adjust minimum IFR altitudes or instrument
procedures as necessary to accommodate the
construction equipment if such action will not have
serious adverse effects on aeronautical operations.
5. Request that the temporary construction
equipment be properly marked and/or lighted if
needed.
b. Temporary Structures - OE notices for
temporary structures are processed in the same
manner as a permanent structure, but require special
consideration in determining the extent of adverse
effect. This is especially true of structures such as
cranes and derricks that may only be at a particular
site for a short time period. As a general policy, it is
considered in the public interest to make whatever
adjustments necessary to accommodate the
temporary structure of 30 days or less if there is no
substantial adverse affect on aeronautical
operations or procedures. However, this policy does
not apply if the aeronautical study discloses that
the structure would be a hazard to aviation.
Reasonable adjustments in aeronautical operations
and modifications to the temporary structure
should be given equal consideration.
6-3-13. CONSIDERING SHIELDING
Shielding as described below should not be confused
with notice criteria as stated in Section 77.15(c).
a. Consideration. Shielding is one of many factors
that must be considered in determining the physical
effect a structure may have upon aeronautical
operations and procedures. Good judgment, in
addition to the circumstances of location and flight
activity, will influence how this factor is considered
in determining whether proposed or existing
structures would be physically shielded.
b. Principle. The basic principle in applying the
shielding guidelines is whether the location and
height of the structures are such that aircraft, when
operating with due regard for the shielding structure,
would not collide with that structure.
c. Limitations. Application of the shielding effect
is limited to:
1. The physical protection provided by existing
natural terrain, topographic features, or surface
structures of equal or greater height than the structure
under study; and
2. The structure(s) providing the shielding
protection is/are of a permanent nature and there are
no plans on file with the FAA for the removal or
alteration of the structure(s).
d. Guidelines. Any proposed construction of or
alteration to an existing structure is normally
considered to be physically shielded by one or more
existing permanent structure(s), natural terrain, or
topographic feature(s) of equal or greater height if the
structure under consideration is located:
1. Not more than 500 feet horizontal distance
from the shielding structure(s) and in the congested
area of a city, town, or settlement, provided the
shielded structure is not located closer than the
shielding structures to any heliport or airport located
within 5 miles of the structure(s).
2. Such that there would be at least one such
shielding structure situated on at least three sides of
the shielded structure at a horizontal distance of not
more than 500 feet.
3. Within the lateral dimensions of any runway
approach surface but would not exceed an overall
height above the established airport elevation greater
than that of the outer extremity of the approach
surface, and located within, but would not penetrate,
the shadow plane(s) of the shielding structure(s).
e. Air traffic shall coordinate with FPO before
applying shielding criteria for precision approach
surface penetrations.
NOTE-
See
FIG 6-3-9 and
FIG 6-3-14.
6-3-14. CONSIDERING SHADOW PLANE
The term "shadow plane" means a surface originating
at a horizontal line passing through the top of the
shielding structure at right angles to a straight line
extending from the top of the shielding structure to
the end of the runway. The shadow plane has a width
equal to the projection of the shielding structure's
width onto a plane normal to the line extending from
the top and center of the shielding structure to the
midpoint of the runway end. The shadow plane
extends horizontally outward away from the
shielding structure until it intersects or reaches the
end of one of the imaginary approach area surfaces;
see
FIG 6-3-15,
FIG 6-3-16, and
FIG 6-3-17.
6-3-15. RECOMMENDING MARKING AND
LIGHTING OF STRUCTURES
a. STANDARDS. FAA standards, procedures,
and types of equipment specified for marking and
lighting structures are presented in AC 70/7460-1,
Obstruction Marking and Lighting. These standards
provide a uniform means to indicate the presence of
structures and are the basis for recommending
marking and lighting to the public. These standards
are the minimum acceptable level of conspicuity to
warn pilots of the presence of structures. They shall
also apply when Federal funds are to be expended for
the marking and lighting of structures.
b. AERONAUTICAL STUDY. All aeronautical
studies shall include an evaluation to determine
whether obstruction marking and/or lighting are
necessary and to what extent. The entire structure or
complex, including closely surrounding terrain and
other structures, must be considered in recommending marking and lighting. A subsequent study may
indicate a need to change an earlier determination by
recommending marking and/or lighting when such
recommendation was not made in the original study
or, in some cases, after a determination was issued.
1. Proposed Structures. A change in runway
length or alignment, a new airport development
project, a change in aeronautical procedures, or other
similar reasons may be cause for additional study of
proposed structures to determine whether marking
and/or lighting are now appropriate even when not
recommended in the original study.
2. Existing Structures. A marking and/or
lighting recommendation may be made at any time.
In making the recommendation consider changes that
have occurred in the vicinity of the structure since the
initial determination was made and include such
factors as increased aircraft activity, the closing of an
airport, changes in IFR and VFR routes, and
shielding by taller structures.
c. RECOMMENDATIONS. Recommend the
marking and/or lighting standard most appropriate
for the height and location of any temporary or
permanent structure that:
1. Exceeds 200 feet in overall height above
ground level at its site or exceeds any obstruction
standard contained in part 77, Subpart C, unless an
aeronautical study shows the absence of such
marking and/or lighting will not impair aviation
safety.
2. Is not more than 200 feet AGL, or is not
identified as an obstruction under the standards of
part 77, Subpart C, but may indicate by its particular
location a need to be marked or lighted to promote
aviation safety.
d. PARTIAL MARKING AND/OR LIGHTING.
Omitting marking and/or lighting on the structure's
bottom section; e.g., the lowest 200 feet of a tall
structure should be discouraged unless that part of the
structure is shielded. Marking and lighting standards
are based on a total system configuration and are only
effective when used as intended. Therefore, the
structure and its location must be given careful
consideration before recommending partial marking
and/or lighting.
e. OMISSION/DELETION OF MARKING
AND/OR LIGHTING. When recommending that
marking and/or lighting be omitted because the
structure is sufficiently conspicuous by its shape,
size, and/or color, include a judgment that the
structure would not blend into any physical or
atmospheric background that may reasonably be
expected in the vicinity.
f. EXCESSIVE MARKING AND/OR
LIGHTING. Recommend specific advisory circular
chapters, paragraphs, and, when appropriate, specific
intensities that address the minimum marking and/or
lighting standards for safety. Recommendation of
specific chapters allow for the use of those chapters
only, although they may contain references to other
chapters. If the sponsor insists on or the FAA finds
that high intensity white lights would not be
objectionable, indicate in the determination that the
FAA does not object to increased conspicuity
provided the lighting is in accordance with guidelines
of AC 70/7460-1, Obstruction Marking and
Lighting.
g. VOLUNTARY MARKING AND/OR
LIGHTING. When it is determined not necessary for
aviation safety, marking and/or lighting may be
accomplished on a voluntary basis. However,
marking and/or lighting should not be a condition of
the determination, but instead, it shall be recommended that, if voluntary, marking and/or lighting be
installed and maintained in accordance with
AC 70/7460-1.
h. HIGH AND MEDIUM INTENSITY WHITE
OBSTRUCTION LIGHTING SYSTEMS:
1. High intensity lighting systems should not be
recommended for structures less than 500 feet above
ground level except when an aeronautical study
shows otherwise. This does not apply to catenary
support structures.
2. Use caution in recommending the use of high
or medium intensity white obstruction lighting
systems, especially in a populated area. Aircraft
operations can be adversely affected where strobe-lighted structures are located in an area of limited
visual cues. These situations can contribute to spatial
disorientation when pilots are maneuvering in
minimum visibility conditions. Marine or surface
vessels and other vehicles, especially on nearby
elevated roadways, could also experience operational
difficulties from strobe lights. External shielding
may minimize adverse effects. Examples are:
(a) At locations within the airport/heliport
environment in a sparsely lighted rural setting.
(b) At an offshore installation.
3. Dual lighting systems should be considered
when a structure is located in or near residential areas,
especially in hilly terrain where some houses are
higher than the base of the structure.
i. LIGHTED SPHERICAL MARKERS. Lighted
spherical markers are available for increased night
conspicuity of high-voltage (69kv or greater)
transmission-line catenary wires. These markers
should be recommended for increased night
conspicuity for such wires when located near
airports, heliports, across rivers, canyons, lakes, etc.
Consider the following when recommending lighted
spherical markers: aeronautical activity, nighttime
operations, low level operations, local weather
conditions, height of wires, length of span, etc. If the
support structures are to be lighted, also consider
lighting the catenary wires. Installation, size, color,
and pattern guidelines can be found in Advisory
Circular 70/7460-1, Obstruction Marking and
Lighting.
j. DEVIATIONS AND MODIFICATION TO
MARKING AND/OR LIGHTING. When the
sponsor or owner of a structure requests permission
to deviate from or modify the recommended marking
and/or lighting, an appropriate aeronautical study
should be made to determine whether the deviation/modification is acceptable, and/or whether the
recommended marking and/or lighting should be
retained.
1. A deviation refers to a change from the
standard patterns, intensities, flashing rates, etc. A
marking and lighting deviation is considered to be
marking patterns or colors and lighting patterns,
intensities, flashing rates, or colors other than those
specified in AC 70/7460-1.
(a) Requests for deviations shall be
forwarded to Airspace and Rules only after an
aeronautical study has been conducted on the
proposal. The results of the study and the regional
recommendation shall be submitted with the request.
(b) Deviations require approval by the
Director of System Operations Airspace and AIM.
Airspace and Rules shall effect all coordination
necessary for issuing the decision to approve or
disapprove. The approval or disapproval decision
shall be forwarded to the region/service area office for
response to the sponsor. Examples of deviations are
contained in AC 70/7460-1.
2. The OES may approve a request for a
modified application of marking and/or lighting.
Examples of modified applications may be found in
AC 70/7460-1. A modified application of marking
and lighting refers to the amount of standard marking
and/or lighting such as:
(a) Placing the standard marking and/or
lighting on only a portion of a structure.
(b) Adding marking and/or lighting in
addition to the standard marking and lighting to
improve the conspicuity of the structure;
(c) Reducing the amount of standard marking
and/or lighting to the extent of eliminating one or the
other as may be considered appropriate.
(d) Adjusting the standard spacing of recommended intermediate light levels for ease of
installation and maintenance as considered
appropriate.
6-3-16. NEGOTIATIONS
Negotiations shall be attempted with the sponsor to
reduce the structure's height so that it does not exceed
obstruction standards, mitigate any adverse effects on
aeronautical operations, air navigation and/or
communication facilities, or eliminate substantial
adverse effect. If feasible, recommend collocation of
the structure with other structures of equal or greater
heights. Include in the aeronautical study file and
determination a record of all the negotiations
attempted and the results. If negotiations result in the
withdrawal of the OE notice, the obstruction
evaluation study may be terminated. Otherwise, the
obstruction evaluation shall be continued to its
conclusion.
6-3-17. CIRCULARIZATION
a. Circularizing a public notice of aeronautical
study provides the opportunity for interested persons
to participate by submitting comments for consideration. The OES shall determine when it is necessary to
distribute a public notice.
1. Normally, any structure that would exceed
obstruction standards, affect an airport, have possible
VFR effect, and/or require a change in aeronautical
operations or procedures should always be
circularized.
2. Circularization is not necessary for the
following types of studies:
(a) A reduction in the height of an existing
structure.
(b) A structure that would be located on a site
in proximity to another previously studied structure,
would have no greater effect on aeronautical
operations and procedures, and the basis for the
determination issued under the previous study could
be appropriately applied.
(c) A proposed structure replacing an existing
or destroyed structure, that would be located on the
same site and at the same or lower height as the
original structure, and marked and/or lighted under
the same provisions as the original structure (this
does not preclude a recommendation for additional
marking/lighting to ensure conspicuity).
(d) A proposed structure that would be in
proximity to, and have no greater effect than, a
previously studied existing structure, and no plan is
on file with the FAA to alter or remove the existing
structure.
(e) A structure that would be temporary and
appropriate temporary actions could be taken to
accommodate the structure without an undue
hardship on aviation.
(f) A structure found to have substantial
adverse effect based on an internal FAA study.
(g) A structure that would exceed part
77.23(a)(2) and would be outside the traffic pattern.
(h) A structure that would affect IFR
operations but would only need FAA comment. For
instance a structure that:
(1) Would raise a MOCA, but not a MEA.
(2) Would raise a MVA.
(3) Would raise a MIA.
3. Circularization for existing structures will be
determined on a case-by-case basis.
b. Each public notice (automated letter CIR) shall
contain:
1. A complete, detailed description of the
structure including, as appropriate, illustrations or
graphics depicting the location of the structure:
(a) On-airport studies. Use airport layout
plans or best available graphic.
(b) Off-airport studies. Use the appropriate
aeronautical chart. Additional illustrations may be
included, as necessary.
2. A complete description of the obstruction
standards that are exceeded, the number of feet by
which the structure exceeds the standards.
3. An explanation of the potential effects of the
structure in sufficient detail to assist interested
persons in formulating comments on how the
structure would affect aeronautical operations.
4. A date by which comments are to be received.
The date established should normally allow
interested persons 30 days in which to submit
comments, but a shorter comment period may be
established depending upon circumstances.
c. Public notices should be distributed to those
who can provide information needed to assist in
evaluating the aeronautical effect of the structure. As
a minimum, the following governmental agencies,
organizations, and individuals should be included on
distribution lists due to their inherent aeronautical
interests:
1. The sponsor and/or his representative.
2. All known aviation interested persons and
groups such as state, city, and local aviation
authorities; airport authorities; various military
organizations within the DOD; flying clubs;
national, state, and local aviation organizations;
flight schools; fixed base operators; air taxi, charter
flight offices; and other organizations or
individuals that demonstrate a specific aeronautical
interest such as county judges and city mayors.
3. Airport owners as follows:
(a) All public-use airports within 13 NM of
the structure.
(b) All private-use airports within 5 NM of
the structure.
4. The specific FAA approach facility, en route
facility (ARTCC), and Automated Flight Service
Station (AFSS) in whose airspace the structure is
located.
5. Flight Standards.
6. An adjacent regional/service area office if the
structure is within 13 NM of the regional state
boundary.
7. As appropriate, state and local authorities;
civic groups; organizations; and individuals who do
not have an aeronautical interest, but may become
involved in specific aeronautical cases, shall be
included in the notice distribution, and given
supplemental notice of actions and proceedings on a
case-by-case basis. Those involved should clearly
understand that the public notice is to solicit
aeronautical comments concerning the physical
effect of the structure on the safe and efficient use of
airspace by aircraft.
8. A proposed structure that penetrates the 40:1
by 35 feet or more, departure slope shall be
circularized to the following:
(a) Aircraft Owners and Pilots Association;
(b) National Business Aviation Association;
(c) Regional Air Line Association;
(d) Department of Defense;
(e) Air Transport Association;
(f) Air Line Pilots Association; and
(g) Other appropriate persons and organizations listed in this section.
d. Document and place in the obstruction
evaluation file the names of each person and/or
organizations to which public notice was sent.
Reference to a distribution code, mailing list, or other
evidence of circularization is sufficient provided a
printout or list of each coded distribution is
maintained for future reference. Also record the time
period during which each printout or list is used. The
retention schedule is listed in Order 1350.15, Records
Organization, Transfer, and Destruction Standards.
e. Consider only valid aeronautical objections or
comments in determining the extent of adverse effect
of the structure. Comments of a non-aeronautical
nature are not considered in obstruction evaluation as
described in part 77.
f. If the sponsor agrees to revise the project so that
it does not exceed obstruction standards and would
have no adverse effect, cancel the public notice,
advise interested parties, as necessary, revise the
obstruction evaluation study, and proceed as
appropriate.
FIG 6-3-14
STANDARDS FOR DETERMINING SHIELDING: CONGESTED PART OF CITY, TOWN, OR
SETTLEMENT
FIG 6-3-15
STANDARDS FOR DETERMINING SHIELDING
FIG 6-3-16
STANDARDS FOR DEVELOPING SHIELDING: PERSPECTIVE OF A SHADOW PLANE
FIG 6-3-17
STANDARDS FOR DETERMINING SHIELDING: EXAMPLES OF SHADOW PLANES
FIG 6-3-18
FREQUENCY PROTECTED SERVICE VOLUME FOR ILS FRONT COURSE
FIG 6-3-19
FREQUENCY PROTECTED SERVICE VOLUME FOR ILS BACK COURSE
FIG 6-3-20
FREQUENCY PROTECTED SERVICE VOLUME FOR VOR
|
