Note: On September 11, 2020, the FAA changed specifications for LED-based red obstruction lights to make them visible to pilots using certain night vision goggle systems.
Effective with implementation of this change in FAA AC 150/5345-43, Specification for Obstruction Lighting Equipment, manufacturers will be required to meet the new specification for certified red LED-based obstruction lights.
Because the new specification ensures the light is visible to pilots operating with night vision goggles, there is risk of a pilot misinterpreting the tower height if a legacy intermediate-level light is replaced with one that meets the new specification unless the top light meets the new specification as well. Therefore, if a legacy specification intermediate-level LED-based light is replaced with a light that meets the new specifications, then the top-level light(s) on the obstruction must also meet the new specification to ensure the entire obstruction is visible during the use of night vision goggles.
2.4.1. Any failure or malfunction that lasts more than thirty (30) minutes and affects a top light, flashing obstruction light regardless of its position, wind turbine lighting fixture, or wind turbine synchronization should be reported immediately by calling Outage Reporting and Notice to Airmen (NOTAM) at 877-487-6867, or in Alaska 800-478- 3576, so a NOTAM can be issued.
For structures that are regulated by the FCC, the FCC advises that noncompliance with notification procedures could subject the Sponsor to penalties or monetary forfeitures.
Voluntarily installed lights (not required by an FAA determination) do not require a NOTAM.
2.4.2. The following information should be specified for outage reporting:
1. Name of persons or organizations reporting the light failures, including any title, address, and telephone number.
2. The type of structure.
3. Location of structure (including latitude and longitude, prominent structures, landmarks, etc.).
4. Height of structure AGL/above mean sea level (AMSL) if known.
5. Return to service date.
6. FCC Antenna Structure Registration Number (for structures that are regulated by the FCC).
Note: When the primary lamp in a double obstruction light fails and the secondary lamp comes on, no report is required.
2.5 Notification of Restoration.
As soon as normal operation is restored, notify Outage Reporting and NOTAM Offices (see Paragraph 2.4.1).
Note: For structures regulated by the FCC, the FCC advises that noncompliance with notification procedures could subject the Sponsor to penalties or monetary forfeitures.
2.6 Federal Communications Commission (FCC) Requirement.
The use of a high-intensity flashing white lighting system on structures located in residential neighborhoods (as defined by applicable zoning laws) trigger requirements for FCC licenses and an environmental assessment.
2.7 Voluntary Marking of Meteorological Evaluation Towers (MET) Less Than 200 Feet (60.96
m) AGL.
The FAA recommends voluntary marking of MET less than 200 feet (60.96 m) AGL in accordance with marking guidance contained in this AC. Historically this guidance has not been applied, however the FAA recognizes the need to address safety impacts to low-level agricultural flight operations and believes that voluntarily marking MET less than 200 feet (60.96 m) AGL in remote and rural areas enhance the conspicuity of these structures.
1. Painting. The MET should be painted in accordance with the standards and criteria contained in Chapters 3 and 15, with alternating bands of aviation orange and white paint. In addition, paragraph 3.3.1 states that all markings should be replaced when faded or otherwise deteriorated.
2. High-visibility sleeves. It is recommended that several high-visibility sleeves be installed on the MET outer guy wires (see Figure A-2). One high- visibility sleeve should be installed on each guy wire, as close to the anchor point as possible, but at a height well above the crop or vegetation canopy. A second sleeve should be installed on the same outer guy wires midway between the location of the lower sleeve and the upper attachment point of the guy wire to the MET.
Spherical markers. It is also recommended that high-visibility aviation orange spherical marker (or cable) balls be attached to the guy wires. Spherical markers should be installed and displayed in accordance to Chapter 11. The FAA, however, recognizes various weather conditions and manufacturing placement standards may affect the placement and use of high-visibility sleeves and/or spherical markers. Thus, some flexibility is allowed when determining sleeve length and marker placement on the MET.
CHAPTER 3. MARKING GUIDELINES
3.1 Purpose.
This chapter provides recommended guidelines to make certain structures conspicuous to pilots during daylight hours. One way to achieve this conspicuity is to paint and/or mark these structures. Recommendations on marking structures can vary, depending on terrain features, weather patterns, geographic location, and the number of structures.
3.2 Paint Colors.
Alternate sections of aviation orange and white paint should be used as the contrast in colors provides maximum visibility of an obstruction. Specific paint standards are contained in Chapter
15.
3.3 Paint Standards.
To be effective, the paint used should meet specific color requirements when freshly applied to a structure. Because all outdoor paints deteriorate with time, and it is not practical to give a maintenance schedule for all climates, surfaces should be repainted when the color changes noticeably or its effectiveness is reduced by scaling, oxidation, chipping, or layers of contamination. The subsequent standards should be followed.
3.3.1 Materials and Application.
The FAA recommends that quality paint and materials be selected to maximize years of service.
The paint should be appropriate for the surfaces to be painted, including any previous coatings, and suitable for the environmental conditions. Surface preparation and paint application should follow the manufacturer’s recommendations.
Note: In-Service Aviation Orange Color Tolerance Charts are available from private suppliers for determining when repainting is required. The color should be sampled on the upper half of the structure, since weathering is greater there.
3.3.2 Surfaces not Requiring Paint.
Ladders, decks, and walkways of steel towers and similar structures do not need to be painted if a smooth surface presents a potential hazard to maintenance personnel. Painting may also be omitted from precision or critical surfaces if the paint would have an adverse effect on the transmission or radiation characteristics of a signal. However, the structure’s overall marking effect should not be reduced.
3.3.3 Skeletal Structures.
Complete all marking/painting prior to or immediately upon completion of construction. This
applies to catenary support structures, radio and television towers, and similar skeletal structures.
To be effective, paint should be applied to all inner and outer surfaces of the framework.
3.4 Paint Patterns.
Various types of paint patterns are used to mark structures. The pattern is determined by the size and shape of the structure. The following patterns are recommended:
3.4.1 Solid Pattern.
Obstacles should be painted aviation orange if the structure’s horizontal and vertical dimensions do not exceed 10.5 feet (3.20 m).
3.4.2 Checkerboard Pattern.
Alternating rectangles of aviation orange and white are normally displayed on the following structures:
1. Water, gas, and grain storage tanks (see Figures A-3, A-4, and A-5).
2. Buildings, as required.
3. Large structures exceeding 10.5 feet (3.20 m) across, having a horizontal dimension that is equal to or greater than the vertical dimension.
3.4.3 Size of Patterns.
The sides of the checkerboard pattern should measure not less than five feet (1.52 m) or more than 20 feet (6.10 m) and should be as nearly square as possible. However, if it is impractical because of the size or shape of a structure, the sides of the patterns may be less than five feet
(1.52 m). The pattern should be arranged so that each outer corner of the structure will be painted aviation orange.
3.4.4 Alternate Bands.
Alternate bands of aviation orange and white are normally displayed on the following structures:
1. Communication towers and catenary support structures.
2. Poles.
3. Smokestacks.
4. Skeletal framework of storage tanks and similar structures.
5. Structures that appear narrow from a side view that are 10.5 feet (3.20 m) or less across, and the horizontal dimension is less than the vertical dimension
6. Coaxial cable, conduits, and other cables attached to the face of a tower. 3.4.5.
3.4.5 Color Band Characteristics.
Bands for structures of any height (see Figure A-6) should be:
1. Equal in width, provided each band is not less than 1 1/2 feet (0.46 m) or more than 100 feet
(30.48 m) wide.
2. Perpendicular to the vertical axis with the bands at the top and bottom painted orange.
3. An odd number of bands on the structure.
4. Equal and in proportion to the structure’s AGL height.
5. Approximately one-seventh the height, if the structure is equal to or less than 700 feet
(213.36 m) AGL. For each additional 200 feet (60.96 m) or fraction thereof, add one additional orange and one additional white band. Table 4-1 shows the required band widths based on the height of the structure.
Table 3-1. Structure Height to Bandwidth Ratio
If a structure is: Then Band Width:
Greater Than
Equal to or Less Than Band Width
10.5 feet (3.20 m)
700 feet (213.36 m)
1/7 of
700 feet (213.36 m)
900 feet (274.32 m)
1/9 of
900 feet (274.32 m)
1,100 feet (335.28 m)
1/11 of
1,100 feet (335.28 m)
1,300 feet (396.24 m)
1/13 of
3.4.6 Structures With a Cover or Roof.
If the structure has a cover or roof, the highest orange band should be continued to cover the entire top of the structure (see Figures A-3 and A-4).
3.4.7 Skeletal Structures Atop Buildings.
If a flagpole, skeletal structure, or similar object is erected on top of a building, the combined height of the object and building will determine whether marking is recommended. However, only the height of the object filed with the FAA determines the width of the color bands.
3.4.8 Partial Marking.
If marking is recommended for only a portion of a structure because the lower portion of the structure is shielded by other objects or terrain, the width of the bands on the exposed portion should still be determined by the overall height of the structure. Paragraph 3.4.5 provides details on calculating the width of the paint bands. A minimum of three bands should be displayed on the exposed portion of the structure. If the exposed portion of the structure is not large enough to have at least three bands, the width of the bands may be reduced equally so that three equally sized bands can be fit. This will ensure that the marking pattern provides sufficient contrast for a pilot to locate the structure.
3.4.9 Teardrop Pattern.
Spherical water storage tanks with a single, circular standpipe support may be marked in a teardrop-striped pattern. The tank should show alternate stripes of aviation orange and white.
The stripes should extend from the top center of the tank to its supporting standpipe. The width of the stripes should be equal, and the width of each stripe at the greatest girth of the tank should not be less than five feet (1.52 m) nor more than 15 feet (4.57 m) (see Figure A-5).
3.4.10 Community Names.
If it is desirable to paint the name of the community on the side of a tank or other structure, the stripe pattern may be broken to serve this purpose. This open area should have a maximum height of three feet (0.91 m) (see Figure A-5).
3.4.11 Exceptions.
Structural designs not conducive to standard markings may be marked as follows:
1. If it is not practical to paint the roof of a structure in a checkerboard pattern, it may be painted solid orange.
2. If a spherical structure is not suitable for an exact checkerboard pattern, the shape of the rectangles may be modified to fit the shape of the surface.
3. Storage tanks not suitable for a checkerboard pattern may have alternating bands of aviation orange and white or a limited checkerboard pattern applied to the upper one- third of the structure.
4. The skeletal framework of certain water, gas, and grain storage tanks may be excluded from the checkerboard pattern.
3.5 Unlighted Markers.
Unlighted markers are used to identify structures and to make them more conspicuous when it is impractical to paint them. Unlighted markers may also be used with aviation orange and white paint when additional conspicuity is necessary for aviation safety. Unlighted markers should be displayed in conspicuous positions on or adjacent to the structures so as to retain the general definition of the structure. They should be recognizable in clear, daytime visibility from a distance of at least 4,000 feet (1,219.20 m) and in all directions from which aircraft are likely to approach. Unlighted markers should be distinctively shaped, i.e., spherical or cylindrical, so that they are not mistaken for items that are used to convey other information. They should be replaced when faded or otherwise deteriorated.
3.5.1 Spherical Markers.
Spherical markers are primarily used to identify overhead wires and catenary transmission lines that are less than 69 kilovolts (kV). Markers may be of another shape, i.e., cylindrical, provided the projected area of such markers is not less than that presented by a spherical marker.
1. Size and Color.
The diameter of the markers used on extensive catenary wires (catenary wires that cross canyons, lakes, rivers, etc.) should not be less than 36 inches (91.44 centimeter (cm)).
Smaller 20-inch (50.80-cm) spheres are permitted on less extensive catenary wires or on power lines below 50 feet (15.24 m) AGL and within 1,500 feet (457.20 m) of an airport runway end. Each marker should be a solid color, specifically aviation orange, white, or yellow.
2. Installation.
a. Spacing. Unlighted markers should be spaced equally along the wire at approximately 200-foot (60.96 m) intervals, or fraction thereof. There should be less space between markers in critical areas near runway ends (i.e., 30 feet to 50 feet (9.14 m to 15.24 m)).
They should be displayed on the highest wire or by another means at the same height as the highest wire. Where there is more than one wire at the highest point, the markers may be installed alternately along each wire if the distance between adjacent markers meets the spacing standard of 200 feet or less. This method distributes the weight and wind- loading factors (see Figures A-21 and A-22).
b. Pattern. An alternating color scheme provides the most conspicuity against all backgrounds. Unlighted markers should be installed by alternating solid-colored markers of aviation orange, white, and yellow. Normally, an orange marker is placed at each end of
a line and the spacing is adjusted (not to exceed 200 feet (60.96 m)) to accommodate the rest of the markers. When less than four markers are used, they should all be aviation orange.
c. Wire Sag. Wire Sag, or droop, will occur due to temperature, wire weight, wind, etc.
Twenty-five feet (7.62 m) is the maximum allowable distance between the highest wire installed with marker balls and the highest wire without marker balls, and must not violate the sag requirements of the transmission line design.
d. Adjacent Lines. Catenary crossings with multiple transmission lines require appropriate markers when the adjacent catenary structure’s outside lines are greater than 200 feet (60.96
m) away from the center of the primary structure. If the outside lines of the adjacent catenary structure are within 200 feet (60.96 m) or less from the center of the primary structure, markers are not required on the adjacent lines.
3.5.2 Flag Markers.
Flags are used to mark certain structures or objects when it is technically impractical to use spherical markers or paint. Flag markers must be mounted at the highest point of the structure to ensure visibility. Some common examples of structures that may utilize this type of markers include, temporary construction equipment and vehicles, oil and drilling rigs, cranes, and derricks.
1. Minimum Size. Each side of the flag marker should be at least two feet (0.61 m) in length.
2. Color Patterns. Flags should be colored as follows:
a. Solid. Aviation orange.
b. Orange and White. Arrange two triangular sections, one aviation orange, and the other white to form a rectangle.
c. Checkerboard. Flags three feet (0.91 m) or larger should be a checkerboard pattern of aviation orange and white squares, each one foot (0.30 m) plus or minus 10 percent.
3. Shape. Flags should be rectangular in shape and have stiffeners to keep them from drooping in calm wind.
4. Display. Flag markers should be displayed around, on top, or along the highest edge of the obstruction. When flags are used to mark extensive or closely grouped obstructions, they should be displayed approximately 50 feet (15.24 m) apart. The flag stakes should be strong enough to support the flags and be higher than the surrounding ground, structures, and/or objects of natural growth.
3.6 Unusual Complexities.
The FAA may also recommend appropriate marking in an area in which grouped obstructions present a common obstruction to air navigation.
3.7 Omission or Alternatives to Marking.
The alternatives listed below require FAA review and concurrence prior to making changes. See subsequent chapters for specific guidance. High-Intensity Flashing White Lighting Systems are more effective than aviation orange and white paint and therefore can be recommended instead of paint marking. This is particularly true under certain ambient light conditions involving the position of the sun relative to the direction of flight. High-intensity lighting systems should not be used on structures 700 feet (213.36 m) AGL or less, however, when operated during daytime, twilight, or 24 hours a day, other methods of marking and lighting may be omitted.
3.7.1 Medium-Intensity Flashing White Lighting Systems are operated during daytime and twilight on structures 700 feet (213.36 m) AGL or less, but generally not on structures less than 200 feet
(60.96 m) AGL. When used, other methods of marking may be omitted.
Note: Sponsors must ensure that alternatives to marking are coordinated with the FCC for structures under its jurisdiction prior to making the change.
CHAPTER 4. LIGHTING GUIDELINE
4.1 Purpose.
This chapter describes the various obstruction lighting systems used to identify structures that have been determined to require added conspicuity. The lighting standards in this AC are the minimum necessary for aviation safety. Recommendations for lighting structures can vary, depending on terrain features, weather patterns, geographic location, and number of structures.
4.2 Standards.
The standards outlined in this AC are based on using light units that meet specified intensities, beam patterns, color, and flash rates as stated in AC 150/5345-43, Specification for Obstruction Lighting Equipment. The AC may be obtained from:
www.faa.gov/airports/resources/advisory_circulars/index.cfm/go/document.current/doc umentnumber/150_5345-43.
4.3 Lighting Systems.
Obstruction lighting may be displayed on structures as follows (refer to subsequent chapters for details):
1. Aviation Red Obstruction Lights. Use flashing lights and/or steady-burning lights during nighttime. Tower structures are typically marked with flashing red lights. Buildings and smaller obstructions located near airports should be marked with steady-burning red lights.
2. Medium-Intensity Flashing White Obstruction Lights. Medium-intensity flashing white obstruction lights may be used during daytime and twilight with automatic reduced intensity selected for nighttime operation. When this system is used on structures 700 feet (213.36 m) AGL or less, other methods of marking and lighting the structure may be omitted. Aviation orange and white paint is always required for daytime marking on structures exceeding 700 feet (213.36 m) AGL. This system is not normally recommended on structures 200 feet
(60.96 m) AGL or less.
3. High-Intensity Flashing White Obstruction Lights. High-intensity flashing white obstruction lights may be used during daytime, with automatically selected reduced intensities for twilight and nighttime operations. When this system is used, other methods of marking and lighting the structure may be omitted. This system should not be used on structures 700 feet
(213.36 m) AGL or less, unless an FAA aeronautical study shows otherwise.
Note: All flashing lights on a structure should flash simultaneously except for catenary support structures, which have a distinct flashing sequence between the levels of lights (see paragraph 12.4).
4. Dual Lighting. This system consists of red lights for nighttime and high- or medium-intensity flashing white obstruction lights for daytime and twilight. When a dual lighting system incorporates medium-intensity flashing white lights on structures 700 feet (213.36 m) AGL or less or high-intensity flashing white lights on structures greater than 700 feet (213.36 m) AGL, other methods of marking the structure may be omitted.
5. Lighted Spherical Markers. Lighted markers are available for increased night conspicuity of high-voltage (69 kV or greater) transmission line catenary wires and should be manufacturercertified as, visible and recognizable from a minimum distance of 4,000 feet (1,219.20 m) under nighttime conditions and under minimum VFR conditions, and have a minimum intensity of at least 32.5 candelas. Markers should be distinctively shaped, i.e., spherical or cylindrical, so that they are not mistaken for items used to convey other information
6. Aircraft Detection Lighting System. Lights are controlled by sensor based systems designed to detect aircraft approaching a single obstacle or group of obstacles and automatically activate the appropriate obstruction lights until the aircraft has departed the area and the lights are no longer needed. This technology reduces the impact of nighttime lighting on nearby communities and migratory birds, as well as, extends the life expectancy of obstruction lights.
7. Obstruction Lights During Construction. As the height of the structure exceeds each level at which permanent obstruction lights would be recommended, two or more lights of the type specified in the determination should be installed at that level. Temporary high- or mediumintensity flashing white lights, if recommended in the determination, should be operated 24 hours a day until all permanent lights are in operation. In either case, two or more lights should be installed on the uppermost part of the structure any time it exceeds the height of the temporary construction equipment. They may be turned off for periods when they could interfere with construction personnel. If practical, permanent obstruction lights should be installed and operated at each level as construction progresses. The lights should be positioned to ensure that a pilot has an unobstructed view of at least one light at each level when approaching from any direction.
8. Obstruction Lights in Urban Areas. When a structure is located in an urban area where there are numerous other white lights (e.g., streetlights), red obstruction lights with painting or a medium-intensity dual system is recommended. White lighting is not normally recommended on structures less than 200 feet (60.96 m) or within 3 NM of an airport.
4.4 Inspection, Repair, and Maintenance.
To ensure the proper candela output for fixtures with incandescent lamps, the voltage provided to the lamp filament should not vary more than plus or minus three percent of the lamp’s rated voltage. The input voltage should be measured at the closest disconnecting means to the lamp fixture with the lamp operating during the hours of normal operation (for strobes, the input voltage of the power supplies should be within 10 percent of rated voltage).
Lamps should be replaced after being in operation for approximately 75 percent of their rated life or immediately upon failure.
Flashtubes in a light unit should be replaced immediately upon failure, when the peak effective intensity falls below specification limits, when the fixture begins skipping flashes, or at the manufacturer’s recommended intervals.
Due to the effects of harsh environments, light fixture lenses should be visually inspected every 24 months or when the light fixture fails for ultraviolet (UV) damage, cracks, crazing, dirt buildup, etc., to ensure the certified light output has not deteriorated (see Chapter 2, paragraph
2.4 for reporting requirements in case of failure). Lenses that have cracks, UV damage, crazing, or excessive dirt buildup should be cleaned or replaced.
4.5 Nonstandard Lights.
Moored balloons, chimneys, church steeples, and similar obstructions may be floodlighted by fixed search light projectors installed at three or more equidistant points around the base of each obstruction. The searchlight projectors should provide an average illumination of at least 15 footcandles (161.46 lux) over the top one-third of the obstruction.
4.6 Placement Factors.
The height above ground level (AGL) of the structure determines the number of light levels. The light levels may be adjusted slightly, but not to exceed 10 feet (3.05 m) when necessary to accommodate guy wires and personnel who replace or repair light fixtures. Except for catenary wire support structures, the following factors should be considered when determining the placement of obstruction lights on a structure:
1. Red Obstruction Lighting Systems. The structure’s overall height, including all appurtenances, such as rods, antennas, and obstruction lights, determines the number of light levels.
2. Medium-Intensity Flashing White Obstruction Lighting Systems. The structure’s overall height, including all appurtenances such as rods, antennas, and obstruction lights, determines the number of light levels.
3. High-Intensity Flashing White Obstruction Lighting Systems. The main structure’s overall height, excluding all appurtenances, such as rods, antennas, and obstruction lights, determines the number of light levels.
4. Dual Obstruction Lighting Systems. The structure’s overall height, including all appurtenances, such as rods, antennas, and obstruction lights, is used to determine the number of light levels for a medium-intensity white obstruction light/red obstruction dual lighting system. The structure’s overall height, excluding all appurtenances, is used to