3. Size and Color.
The diameter of the unlighted markers used on extensive catenary wires that cross canyons, lakes, rivers, etc., should not be less than 36 inches (91.44 cm). The 20-inch (50.80-cm) markers, or smaller 12-inch (30.48-cm) markers are permitted on less extensive catenary wires or on power lines below 50 feet (15.24 m) above the ground and within 1,500 feet
(457.20 m) of an airport runway end. Each unlighted marker should be a solid color;
specifically aviation orange, white, or yellow. For transmission lines that are configured in a “double-bundled” arrangement and would typically require the larger 36-inch markers, the next smaller size marker may be used to prevent the marker from rubbing against the parallel transmission line.
Note: For the purposes of this advisory circular, the term “extensive” is used to describe catenary wire crossings that extend across an open area that an aircraft could be reasonably expected to fly at or below the altitude that the catenary wires are suspended.
“Less extensive” is used to describe catenary wire crossings that extend across an open area that an aircraft could be reasonable expected to fly at or above the same altitude.
4. Installation.
a. Spacing. Unlighted markers should be spaced equally along the wire at intervals of approximately 200 feet (60.96 m), or a fraction thereof. Intervals between markers should be less in critical areas near runway ends, i.e., 30 feet to 50 feet (9.14 m to 15.24 m). The unlighted markers may be installed alternately along each wire if the distance between adjacent markers meets the 200-foot (60.96 m) spacing standard. This method allows the weight and wind loading factors to be distributed (see Figure A-21).
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. The maximum sag distance between the line holding the unlighted markers and the next lowest catenary wire should be no more than 25 feet (7.62 m), and it should 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 catenary structure (see Figure A-25). If the outside lines of the adjacent catenary structure are within 200 feet (60.96 m) or less from the center of the primary catenary structure, markers are not required on the adjacent line.
11.4 Catenary Lighting Standards.
When using medium-intensity flashing white (L-866), high-intensity flashing white (L-857), dual medium-intensity (L-866/L-885), or dual high-intensity (L-857/L-885) lighting systems operated 24 hours a day, other marking of the support structure is not necessary.
1. Levels. A system of three levels of sequentially flashing light units should be installed on each supporting structure or adjacent terrain. One level should be installed at the top of the structure, one at the height of the lowest point in the catenary wire, and one level approximately midway between the other two light levels. In general, the middle level should be at least 50 feet (15.24 m) from the other two levels. The middle light unit may be omitted when the distance between the top and the bottom light levels is less than 100 feet (30.48 m).
a. Top Levels. One or more lights should be installed at the top of the structure to provide 360-degree coverage, ensuring an unobstructed view. If the installation presents a potential danger to maintenance personnel or inhibits lightning protection, the top level of lights may be mounted as low as 20 feet (6.10 m) below the highest point of the structure.
b. Horizontal Coverage. The light units at the middle and bottom levels should be installed to provide a minimum of 180-degree coverage, centered perpendicularly to the flyway. When a catenary crossing is situated near a bend in a river, canyon, etc., or is not perpendicular to the flyway, the horizontal beam should be directed to provide the most effective light coverage to warn pilots approaching from either direction of the catenary wires.
c. Variation. The vertical and horizontal arrangements of the lights may be subject to the structural limits of the towers and/or adjacent terrain. A tolerance of 20 percent from uniform spacing of the bottom and middle light is allowed. If the base of the supporting structure(s) is higher than the lowest point in the catenary, such as a canyon crossing, one or more lights should be installed on the adjacent terrain at the level of the lowest point in the span. These lights should be installed on the structure or terrain at the height of the lowest point in the catenary (see Figure A-25).
2. Flash Sequence and Duration. The flash sequence for catenary wire support structures should be middle, top, and bottom with all lights on the same level flashing simultaneously. This pattern of flashes is designed to present a unique signal that pilots should interpret as a warning that catenary wires are in the vicinity of the lights. The time intervals for the sequence and duration of the flash pattern are outlined in FAA AC 150/5345-43, Specification for Obstruction Lighting Equipment. If Light-Emitting Diode (LED) obstruction light fixtures are used to light catenary wires, a slower flash rate of 40 fpm is allowed to enable each light fixture to make a well-defined flash so that the middle-topbottom flash pattern will be easily recognized. Field experience has shown that LED fixtures flashing at 60 fpm, as specified in AC 150/5345-43, do not have enough time to turn off in between flash cycles, and appear as if they are steady-burning. Slowing the flash rate to 40
fpm promotes a cleaner, crisper presentation for the pilot to recognize. In the event there are only two levels of lights, the lights should simply alternate at the same flash rate/duration as if there were three lights.
3. Synchronization. Although not required, it is preferred that the corresponding light levels on associated supporting towers of a catenary crossing flash simultaneously.
4. Structures 700 feet (213.36 m) AGL or less. When medium-intensity white lights (L-866) are operated 24 hours a day or when a dual red/medium-intensity light system (L-866 daytime and twilight/L-885 nighttime) is used, marking can be omitted. When using a mediumintensity white light (L-866) or a flashing red light (L-885) during twilight or nighttime only, paint should be used for daytime marking.
5. Structures exceeding 700 feet (213.36 m) AGL. When high-intensity white lights (L-857) are operated 24 hours a day or when a dual red/high-intensity system (L-857 daytime and twilight/L-885 nighttime) is used, marking can be omitted. This system should not be used on structures 700 feet (213.36 m) or less unless an FAA aeronautical study shows otherwise.
When a flashing red obstruction light (L-885), a medium-intensity (L-866) flashing white lighting system, or a high-intensity white lighting system (L-857) is used for nighttime and twilight only, paint should be used for daytime marking.
11.5 Control Device.
The light intensity is controlled by a device (photocell) that changes the intensity when the ambient light changes. The illuminance-sensing device should, if practical, face the northern sky in the Northern Hemisphere and the lighting system should automatically change intensity steps when the northern sky illuminance reaching a north-facing vertical surface is as follows:
1. Day-to-Twilight (L-857 System). This should not occur before the illumination drops to 60 foot-candles (645.83 lux) but should occur before it drops below 35 foot-candles (376.74 lux).
2. Twilight-to-Night (L-857 System). This should not occur before the illumination drops below 5 foot-candles (53.82 lux) but should occur before it drops below 2 foot-candles (21.53 lux).
3. Night-to-Day. The intensity changes listed in subparagraph 11.4.1 and 11.4.2 above should be reversed when changing from the night-to-day mode.
4. Day-to-Night (L-866 or L-885/L-866). This should not occur before the illumination drops below 5 foot-candles (563.82 lux) but should occur before it drops below 2 foot-candles
(21.53 lux).
5. Night-to-Day. The intensity changes listed in subparagraph 11.1.4.4 above should be reversed when changing from the night-to-day mode.
6. Red Obstruction (L-885). The red lights should not turn on until the illumination drops below 60 foot-candles (645.83 lux) but should occur before reaching a level of 35 foot-candles
(367.74 lux). Lights should not turn off before the illumination rises above 35 foot-candles
(367.76 lux) but should occur before reaching 60 foot-candles (645.83 lux).
11.6 Area Surrounding Catenary Wire Support Structures.
The area in the immediate vicinity of the supporting structure’s base should be clear of all items and/or objects of natural growth that could interfere with the line-of-sight between a pilot and the structure’s lights.
11.7 Three or More Catenary Wire Support Structures.
Where a catenary wire crossing requires three or more supporting structures, the inner structures should be equipped with enough light units per level to provide full 360- degree coverage across rivers, canyons, lakes, areas of known risk to aviation, etc.
CHAPTER 12. MARKING AND LIGHTING MOORED BALLOONS AND KITES
12.1 Purpose.
The purpose of marking and lighting moored balloons, kites, and their cables or mooring lines is to indicate the presence and general definition of these objects to pilots when approaching from any direction.
12.2 Standards.
These marking and lighting standards pertain to all moored balloons and kites that require marking and lighting under 14 CFR, Part 101.
12.3 Marking.
Flag markers should be used on mooring lines to warn pilots of their presence during daylight hours.
1. Display. Markers should be displayed at no more than 50-foot (15.24 m) intervals and should be visible for at least 1 SM (1.61 km).
2. Shape. Markers should be rectangular in shape and not less than 2 feet (0.61 m) in length.
Stiffeners should be used in the borders to expose a large area and to prevent drooping in calm wind or wrapping around the cable.
3. Color Patterns. One of the following color patterns should be used:
a. Solid Color. Aviation orange.
b. Orange and White. Two triangular sections, one of aviation orange and the other white, combined to form a rectangle.
12.4 Purpose.
Flashing obstruction lights should be used on moored balloons or kites and their mooring lines to warn pilots of their presence during the hours between sunset and sunrise and during periods of reduced visibility. These lights may be operated 24 hours a day.
1. Systems. Flashing red (L-864) or medium-intensity white lights (L-865) may be used to light moored balloons or kites. High-intensity lights (L-856) are not recommended.
2. Display. Simultaneously flashing lights should be displayed on the top, nose, and tail sections, as well as the tether cable approximately 15 feet (4.57 m) below the craft to define the extremes of size and shape. Additional lights should be equally spaced along the cable’s overall length for each 350 feet (106.68 m), or fraction thereof.
3. Exceptions. When the requirements of this paragraph cannot be met, floodlights may be used.
12.5 Operational Characteristics.
The light intensity is controlled by a device (photocell) that changes the intensity when the ambient light changes. The system should automatically turn the lights on and change intensities as ambient light conditions change. The reverse order should apply in changing from nighttimeto-daytime operation.
CHAPTER 13. MARKING AND LIGHTING WIND TURBINES
13.1 Purpose.
This chapter provides guidelines for the marking and lighting applicable to single wind turbines and wind turbine farms. For the purpose of this AC, wind turbine farms are defined as a wind turbine development that contains more than three turbines. The recommended marking and lighting of these structures is intended to provide day and night conspicuity and to assist pilots in identifying and avoiding these obstacles.
13.2 General Standards.
The development of wind turbine farms is a very dynamic process, which changes based on the terrain. Each wind turbine farm is unique, therefore it is important that a lighting plan is developed that provides sufficient safety for air traffic. When developing lighting plans for wind turbine farms, it is best to use an aerial-view map or diagram of the turbine farm to plan the location of the required lighting. This way, a certain degree of strategy planning can be applied, which, in many instances, results in a minimal number of lights. Proximity to airports and VFR routes, extreme terrain where heights may vary widely, and local flight activity should be considered when developing a lighting plan. The following guidelines are recommended for wind turbines.
13.3 Wind Turbine Configurations.
Prior to marking and lighting the wind turbine farm, the configuration and the terrain of the wind turbine farm should be determined. The following is a description of the most common configurations (see Figure A-26):
1. Linear. Wind turbine farms in a direct, consecutive configuration, often located along a ridgeline, the face of a mountain, or along borders of a mesa or field. The line may be ragged in shape or be periodically broken, and may vary in size from just a few turbines to many turbines forming a line that is several miles long.
2. Cluster. Wind turbine farms arranged in circular configuration. A cluster is typically characterized by having a pronounced perimeter, with various turbines placed inside the circle at various, erratic distances throughout the center of the circle.
3. Grid. Wind turbine farms arranged in a geographical shape, such as a square or a rectangle, in which the turbines are placed a consistent distance from each other in rows, giving the appearance that they are part of a square pattern.
13.4 Marking Standards.
13.4.1 Wind turbines should be painted white or light grey, as these colors have been shown to be the most effective method for providing daytime conspicuity (see Figure A-26). Wind turbine manufacturers typically use a European color-matching system that is referred to as the RAL Color Standard. The RAL system uses a four-digit code to identify a specific color of paint, for example, an RAL 9xxx code would represent a color in the white/black range. The preferred white paint color is pure white, RAL 9010, or an equivalent, however most wind turbines currently produced are painted light grey, RAL 7035, which is the darkest acceptable off-white paint allowed. Any shade of white between these two RAL specifications is strongly recommended (see Table 13-1).
Table 13-1. Wind Turbine Paint Standard Colors
Color
RAL Number
Pure White (preferred color)
9010
Light Grey (Darkest Acceptable)
7035
13.4.2 In geographic areas that experience lengthy periods of snow cover (i.e., Alaska), and where it is deemed necessary, the mast of the turbine may be painted alternating bands of aviation orange and white to provide additional contrast against the snow. The nacelle and blades of the turbine must remain solid white or light grey (see Figure A-27).
13.4.3 Blades or blade tips must not be painted or manufactured in colors to camouflage wind turbines with the surrounding terrain.
13.4.4 For turbines that are constructed with lattice-type masts, the mast structure must be painted with alternating bands of aviation orange and white paint, in accordance with Chapter 3. The turbine’s nacelle and blades must remain solid white or light grey.
13.5 Lighting Standards.
13.5.1 Studies have shown that red lights provide the most conspicuity to pilots, therefore during nighttime hours and periods of reduced visibilities, wind turbine obstruction lighting should consist of FAA L-864 aviation red flashing, strobe, or pulsed obstruction lights. Any array of flashing, strobe, or pulsed obstruction lighting should be synchronized to flash simultaneously (within ±1/20 second (0.05 second) of each other). Light fixtures should be placed as high as
possible on the turbine nacelle so they are visible by a pilot approaching from any direction (see Figure A-28). Should any lighting fixture or the lighting system synchronization fail, a lighting outage report should be prepared in accordance with Chapter 2, paragraph 2.4.
Daytime lighting of wind turbines is not required. See paragraph 14.4 for daytime marking requirements.
13.5.2 In most cases, not all wind turbine units within a wind turbine farm need to be lighted.
Obstruction lights should be placed along the perimeter of the wind turbine farm so that there are no unlit separations or gaps more than 1/2 SM (0.80 km). Wind turbines within a grid or cluster should not have an unlighted separation or gap of more than 1 SM (1.61 km) across the interior of a grid or cluster of turbines (see Figure A-25).
1. Linear Turbine Configurations: Lights should be placed on the turbine positioned at each end of a line or string of turbines. Lights should also be placed along the line of turbines so that there is no more than a 1/2 SM (804.67 m) gap between the lighted turbines. In the event the gap between lights on the last segment of turbines is significantly short, it may be appropriate to move the lights on the turbine string back toward the starting point to present a wellbalanced string of lights. High concentrations of lights should be avoided.
2. Cluster Turbine Configurations. A turbine should be selected as a starting point along the outer perimeter of the cluster. The turbine should be lighted, and a light should be placed on the next turbine along the perimeter of the cluster (clockwise or counterclockwise) so that no more than a 1/2 SM (804.67 m) gap exists. This pattern should be continued around the perimeter of the cluster until the starting point is reached. In the event that the gap between the lights on the last segment of turbines is significantly short, it may be appropriate to move the lights along the perimeter of the cluster back toward the starting point to present a wellbalanced perimeter of lights. If the distance across the cluster is greater than 1 SM (1.61 km), additional lights should be placed on other turbines throughout the center of the cluster so that there are no unlighted gaps across the cluster. For example, if the distance across a wind turbine farm is 1.8 SM (2.90 km), a light should be placed on a turbine at approximately every 0.9 SM (1.45 km).
3. Grid Turbine Configurations. Turbines on the corners of the farm should be lit, and then use the same concept for selecting which turbines should be lit as outlined in paragraph 13.5.3.
13.5.3 Special Considerations.
Occasionally, some wind turbines may be located apart from the main group of turbines. If one or two wind turbines protrude from the general limits of the turbine farm, these turbines should be lighted in addition to those identified in the main group.Additional lighting may be necessary on wind turbines located on the interior of a cluster or grid configuration whose height is 100 feet
(30.48 m) or higher than the other wind turbines located within the farm.
13.6 Wind Turbines Above 499 Feet (152.10 m).
13.6.1 For wind turbines with a rotor tip height, while at top dead center, greater than 499 feet (152.10
m) AGL, but less than 699 feet (213.06 m) AGL, the turbines should be lighted in accordance with paragraph 13.5. In addition to these requirements, the top of the turbine’s nacelle should be equipped with a second L-864 flashing red light (see Figure A-28).
13.6.2 The two obstruction lights should be arranged horizontally, positioned on opposite sides of the nacelle, visible to a pilot approaching from any direction, and flash simultaneously. Using this lighting configuration ensures the conspicuity of turbines in this size category.
13.6.3 In the event one of the two obstruction lights fails, no light failure notification is required;
however, the light should be restored to service as soon as possible.
13.6.4 All turbines within this size category should be illuminated, regardless of their location within a wind turbine farm, and should be configured to flash simultaneously with the other turbines in the same farm. This requirement ensures the pilots operating at low altitudes above 500 feet AGL have sufficient warning that a wind turbine obstruction may be within their flight path.
13.7 Wind Turbines at or Above 699 Feet (213.36 m).
13.7.1 For wind turbines with a rotor tip height, while at top dead center, at or above 699 feet (213.06
m) AGL, additional lighting is required. All wind turbines of this size, regardless of number or configuration should be lighted.
13.7.2 In addition to the lighting identified in paragraphs 13.5 and 13.6, an additional level of lights is required at a point midway between the top of the nacelle and ground level. The location of the additional lights may be adjusted as necessary to allow mounting at a seam within the turbine’s mast.
13.7.3 The additional level of lights should consist of a minimum of three L-810 F flashing red lights configured to flash in unison with the two L-864 red flashing lights located at the top of the nacelle at a rate of 30 fpm (± 3 fpm). The L-810 F lights should be spaced at equal distances around the mast to ensure a pilot approaching from any direction has an unobstructed view of at least two of the lights (see Figure A-28).
13.7.4 For wind turbine structures with a mast diameter greater than 20 feet (6.10 m), four L- 810 red lights should be used.
13.7.5 All turbines within this size category should be illuminated, regardless of their location within a turbine farm, and should be configured to flash simultaneously with the other turbines in the same farm. This requirement ensures the pilots operating at low altitudes above 500 feet AGL have sufficient warning that a wind turbine obstruction may be within their flight path.
13.8 Lighting of Wind Turbines During Construction Phase.
To ensure proper conspicuity of turbines at night during construction, all turbines should be lighted with temporary lighting once they reach a height of 200 feet (60.96 m) or greater until the permanent lighting configuration is turned on. If practical, permanent obstruction lights should be installed and operated at each level as construction progresses. As the structure’s height continues to increase, the temporary lighting should be relocated to the structure’s uppermost height (see Figure A-30). An L-810 steady-burning red light must be used to light the structure during the construction phase, if the permanent L-864 flashing-red lights are not in place. The temporary lighting may be turned off for short periods if they interfere with construction personnel. If power is not available, turbines should be lighted with a self-contained, solarpowered, LED, steady-burning red light that meets the photometric requirements of an FAA L- 810 lighting system. The lights should be positioned to ensure a pilot has an unobstructed view of at least one light at each level. Using a NOTAM to justify not lighting the turbines until the entire project is completed is prohibited.
13.9 Lighting and Marking of Airborne Wind Turbines.
The FAA is currently conducting research to develop special lighting and marking standards for Airborne Wind Turbines. Sponsors should consult with their respective FAA OE Specialists for updated information.
13.10 Lighting and Marking of Offshore Wind Turbines.
FAA lighting and marking recommendations for Offshore Wind Turbines applies to structures in United States territorial seas, which extends from the coastline to 12 NM offshore. The Bureau of Ocean Energy Management (BOEM), which maintains jurisdiction of land leases beyond the 12 NM, is developing their own marking and lighting standards for offshore wind turbines and new construction must comply with those standards.
CHAPTER 14. MARKING AND LIGHTING TEMPORARY STRUCTURES
14.1 Purpose.
This chapter provides general guidelines for marking and lighting temporary structures, such as construction equipment, cranes, derricks, oil and drilling rigs, etc. The purpose of marking and lighting these obstructions is to indicate the presence and general outline of the structure to assist pilots when approaching from any direction to identify and avoid these obstacles. These guidelines are not to be considered all-inclusive, each obstacle must be evaluated individually and the determination will provide lighting requirements that are specific to the structure.
14.2 General Standards.
Due to the temporary nature, potential mobility, and ability to instantaneously extend to full height, accommodations must be made to mitigate the effects of these structures on the airspace for safe operations. Temporary structures are unique based on the structure type, size, and use, and the aeronautical study evaluates the potential effect on airspace. Proximity to airports, navigational aids (NAVAIDS), air routes, and local flight activity, as well as the duration of the project are considered during the evaluation process.
Marking and/or lighting of these structures is intended to provide day and night conspicuity and to assist pilots in identifying and avoiding these obstacles. In some cases, the Sponsor will also be required to initiate a NOTAM to provide additional mitigation procedures for the safe operation of the temporary obstacle due to the proximity of these aviation elements.
14.3 Marking Standards.
Marking is used to increase conspicuity of structures for daytime conditions. Flags are used to mark certain structures or objects when it is technically impractical to use paint. When using paint, various types of paint colors and patterns are used to mark structures and the pattern should ensure the paint contrasts with the surrounding environment.
14.3.1 Flag Markers.
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. Refer to Section
3.5.2 for full details.
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 colored flag must be aviation orange.