13-1 CHAPTER 13. MARKING AND LIGHTING WIND TURBINES
13.1 Purpose.
This chapter provides guidelines for the marking and lighting of wind turbine farms.
These guidelines are 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 be developed that provides sufficient safety for air traffic. 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.
1. Linear—wind turbine farms in a direct, consecutive configuration, often located along a ridge line, 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. Wind turbine manufacturers typically use a European color-matching system that is referred to as the RAL Color Standard. Unlike the Federal Specification 595, the RAL system used 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, and an RAL 6xxx code would be in
13-2 the grey range. Most wind turbines currently produced are painted light grey, RAL 7035, which is the darkest acceptable off-white paint allowed. The preferred white paint color is pure white, RAL 9010, or an equivalent. 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 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 shall remain solid white or light grey. (See Figure A-24 in Appendix A.)
13.4.3 Blades or blade tips shall not be painted or manufactured in colors to camouflage wind turbines with the surrounding terrain. (See Figure A-25 in Appendix A.)
13.4.4 For turbines that are constructed with lattice-type masts, the mast structure shall be painted with alternating bands of aviation orange and white, in accordance with Chapter 3. The turbine’s nacelle and blades shall remain solid white or light grey.
13.5 Lighting Standards.
13.5.1 Nighttime wind turbine obstruction lighting should consist of FAA L-864 aviation red flashing, strobe, or pulsed obstruction lights. Studies have shown that red lights provide the most conspicuity to pilots.
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 statute mile (sm) (804 m). Wind turbines within a grid or cluster should not have an unlighted separation or gap of more than 1 sm (1.6 km) across the interior of a grid or cluster of turbines. (See Figure A-26 in Appendix A.)
13.5.3 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).
13.5.4 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.
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13.5.5 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-23 in Appendix A.)
13.5.6 Daytime lighting of wind turbines is not required. See paragraph 13.4 for daytime marking requirements.
13.5.7 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 plan can be applied, which, in many instances, results in a minimal number of lights.
13.5.8 For 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 (2,640-foot (805-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 well-balanced string of lights. High concentrations of lights should be avoided. (See Figure A-26 in Appendix A.)
13.5.9 For 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 (2,640-foot (805-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 well-balanced perimeter of lights. If the distance across the cluster is greater than 1 sm, additional lights should be placed on other turbines throughout the center of the cluster so that there are no unlighted gaps across the cluster. (See Figure A-26 in Appendix A.) (Example: If the distance across a wind turbine farm is 1.8 sm (2.9 km), a light should be placed on a turbine at approximately every 0.9 sm (1.4 km).
13.5.10 For 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 13.5.9.
13.5.11 Special Considerations.
13.5.11.1 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.
13.5.11.2 Additional lighting may be necessary on wind turbines located on the interior of a cluster or grid configuration whose height is 100 feet (30 m) or higher than the other wind turbines located within the farm.
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13.6 Wind Turbines Above 499 Feet.
13.6.1 For wind turbines with a rotor tip height, while at top dead center, greater than 499 feet (153 m) AGL, but less than 699 feet 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-23 in Appendix A.)
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. (See Figure A-23 in Appendix A.) This lighting configuration ensures the turbines in this size category are always lighted.
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 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 m).
13.7.1 For wind turbines with a rotor tip height, while at top dead center, at or above 699 feet (213 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 paragraph 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.
13.7.2.1 The additional level of lights should consist of a minimum of three L-810 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-810s should be spaced at equal distances around the mast. The light should be installed to ensure a pilot approaching from any direction has an unobstructed view of at least two of the lights. (See Figure A-23 in Appendix A.)
13.7.2.2 For wind turbine structures with a mast diameter greater than 20 feet (6 m), four L-810 red lights should be used.
13.7.2.3 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
13-5 ensures the pilots operating at 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 (61 m) or greater until the permanent lighting configuration is turned on. As the structure’s height continues to increase, the temporary lighting should be relocated to the structure’s uppermost height. The temporary lighting may be turned off for short periods if they interfere with construction personnel. If practical, permanent obstruction lights should be installed and operated at each level as construction progresses. An L-810 steadyburning red light shall be used to light the structure during the construction phase, if the permanent L-864 flashing-red lights are not in place. If power is not available, turbines should be lighted with a self-contained, solar-powered, 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 (D) 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 apply to structures out to 12 NM from the coast of the United States, which is the extent of the territorial seas. The Bureau of Ocean Energy Management (BOEM), which maintains jurisdiction of land leases beyond the 12 NM, may also require compliance with the marking and/or lighting recommendations identified in this AC.
14-1 CHAPTER 14. AIRCRAFT DETECTION LIGHTING SYSTEMS
14.1 Purpose.
Aircraft Detection Lighting Systems (ADLS) are sensor-based systems designed to detect aircraft as they approach an obstruction or group of obstructions; these systems automatically activate the appropriate obstruction lights until they are no longer needed by the aircraft. This technology reduces the impact of nighttime lighting on nearby communities and migratory birds and extends the life expectancy of obstruction lights.
14.2 General Standards.
14.2.1 The system should be designed with sufficient sensors to provide complete detection coverage for aircraft that enter a three-dimensional volume of airspace, or coverage area, around the obstruction(s) (see Figure A-27 in Appendix A), as follows:
1. Horizontal detection coverage should provide for obstruction lighting to be activated and illuminated prior to aircraft penetrating the perimeter of the volume, which is a minimum of 3 NM (5.5 km) away from the obstruction or the perimeter of a group of obstructions.
2. Vertical detection coverage should provide for obstruction lighting to be activated and illuminated prior to aircraft penetrating the volume, which extends from the ground up to 1,000 feet (304 m) above the highest part of the obstruction or group of obstructions, for all areas within the 3 NM (5.5 km) perimeter defined in subparagraph 14.2.1 1 above.
3. In some circumstances, it may not be possible to meet the volume area defined above because the terrain may mask the detection signal from acquiring an aircraft target within the 3 NM (5.5 km) perimeter. In these cases, the sponsor should identify these areas in their application to the FAA for further evaluation.
4. In some situations, lighting not controlled by the ADLS may be required when the 3 NM (5.5 km) perimeter is not achievable to ensure pilots have sufficient warning before approaching the obstructions.
14.2.2 The ADLS should activate the obstruction lighting system in sufficient time to allow the lights to illuminate and synchronize to flash simultaneously prior to an aircraft penetrating the volume defined above. The lights should remain on for a specific time period, as follows:
1. For ADLSs capable of continuously monitoring aircraft while they are within the 3 NM/1,000 foot (5.5 km/304 m) volume, the obstruction lights should stay on until the aircraft exits the volume. In the event detection of the aircraft is lost while being continuously monitored within the 3 NM/1,000 foot (5.5 km/304 m) volume, the ADLS should initiate a 30-minute timer and keep the obstruction lights on until the timer expires. This should provide the untracked aircraft sufficient time to exit the area and give the ADLS time to reset.
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2. For ADLSs without the capability of monitoring aircraft targets in the 3 nm/1,000 foot (5.5 km/304 m) volume, the obstruction lights should stay on for a preset amount of time, calculated as follows:
a. For single obstructions: 7 minutes.
b. For groups of obstructions: (the widest dimension in nautical miles + 6) x 90 seconds equals the number of seconds the light(s) should remain on.
14.2.3 Acceptance of ADLS applications will be on a case-by-case basis and may be modified, adjusted, or denied based on proximity of the obstruction or group of obstructions to airports, low-altitude flight routes, military training areas, or other areas of frequent flight activity. It may be appropriate to keep certain obstructions closest to these known activity areas illuminated during the nighttime hours, while the remainder of the group’s obstruction lighting is controlled by the ADLS.
14.2.4 Project sponsors requesting ADLS use should include in their application maps or diagrams indicating the location of the proposed sensors, the range of each sensor, and a visual indication showing how each sensor’s detection arc provides the full horizontal and vertical coverage, as required under paragraph 14.2.1. In the event that detection coverage is not 100 percent due to terrain masking, project sponsors should provide multiple maps or diagrams that indicate coverage at the affected altitudes. A sample diagram is shown in Figure A-27 in Appendix A.
14.2.5 Types of ADLS Component or System Failure Events.
1. In the event of an ADLS component or system failure, the ADLS should automatically turn on all the obstruction lighting and operate in accordance with this AC as if it was not controlled by an ADLS. The obstruction lighting must remain in this state until the ADLS and its components are restored.
2. In the event that an ADLS component failure occurs and an individual obstruction light cannot be controlled by the ADLS, but the rest of the ADLS is functional, that particular obstruction light should automatically turn on and operate in accordance with this AC as if it was not controlled by an ADLS, and the remaining obstruction lights can continue to be controlled by the ADLS. The obstruction lighting will remain in this state until the ADLS and its components are restored.
3. Complete light failure should be addressed in accordance with Chapter 2 paragraph 2.4.
14.2.6 The ADLS’s communication and operational status shall be checked at least once every 24 hours to ensure both are operational.
14.2.7 The ADLS should be able to detect an aircraft with a cross-sectional area of 1 square meter or more within the volume, as required in subparagraphs 14.2.1 1 and 14.2.1 2.
14.2.8 Each ADLS installation should maintain a log of activity data for a period of no less than the previous 15 days. This data should include, but not be limited to, the date, time, duration of all system activations/deactivations, track of aircraft activity,
14-3 maintenance issues, system errors, communication and operational issues, lighting outages/issues, etc.
14.2.9 Operational Frequencies.
1. Unlicensed devices (including FCC Part 15) devices cannot be used for this type of system.
2. Any frequency used for the operation of ADLS must be individually licensed through the FCC.
14.3 Voice/Audio Option.
14.3.1 ADLS may include an optional voice/audio feature that transmits a low-power, audible warning message to provide pilots additional information on the obstruction they are approaching.
14.3.2 The audible transmission should be in accordance with appropriate FAA and FCC regulations.
14.3.3 The audible transmission should be over an aviation frequency licensed by the FCC and authorized under the Code of Federal Regulations Title 47- Part 87.483 (excluding
121.5 MHz).
Note: Using air traffic control frequencies in the 117.975-MHz to 137-MHz frequency band is prohibited for this operation.
14.3.4 The audible message should consist of three quick tones, followed by a verbal message that describes the type of obstruction the system is protecting. Appropriate terms to be used include tower(s), wind turbine(s), or power line(s).
14.3.5 The audible message should be repeated three times or until the system determines the aircraft is no longer within the audible warning area defined in the following paragraph.
14.3.6 The audible message should be considered as a secondary, final warning and should be activated when an aircraft is within 1/2 NM (926 m) horizontally and 500 feet (152 m) vertically of the obstruction. The use of, or variation to, the audible warning zone may occur, depending on site-specific conditions or obstruction types.
Appendix A A-1 APPENDIX A. SPECIFICATIONS FOR OBSTRUCTION LIGHTING EQUIPMENT
CLASSIFICATION Table A-1. FAA-Approved Obstruction Lighting Fixtures Type Symbol Description L-810
Steady-Burning - RED Single Obstruction Light L-810
Steady-Burning – RED Double Obstruction Light L-856
High-Intensity Flashing – WHITE Obstruction Light (40 FPM) L-857
High-Intensity Flashing – WHITE Catenary Light (60 FPM) L-864
Medium-Intensity Flashing – RED Obstruction Light (20-40 FPM) L-865
Medium-Intensity Flashing – WHITE Obstruction Light (40-FPM) L-866
Medium-Intensity Flashing - WHITE Catenary Light (60-FPM) L-864/L-865
Medium-Intensity Flashing Dual – RED / WHITE Obstruction Light (20-40 FPM) Obstruction Light (40 FPM) L-885
Low-Intensity Flashing - RED Red Catenary Light (60 FPM) FPM = Flashes Per Minute
Appendix A
CATENARY UNLIGHTED MARKERS Required for transmission lines less than 69 kV Recognizable from a minimum distance of 4,000 ft (1,219 m) Wire markers may be staggered over the catenary to enable better wind load distribution 200 ft (61 m)
- Violation Area (Above 200 ft (61 m) AGL) 25 ft (8 m) max distance unless line design sag requirements are greater Unlighted Marker Ball Extensive catenary wires: min 36-inch- (91-cm-) diameter markers; less extensive catenary wires: 20-inch- (51-cm-) or 12-inch-
(30.48-cm-) diameter markers.
Evenly spaced along the wire at approximately 200-ft (61-m) intervals.
Lighted markers should be a solid color, such as aviation orange, white or yellow.
Lighted markers should alternate aviation orange, white, yellow with aviation orange markers positioned at each end.
If less than four lighted markers are on the line, all markers should be aviation orange.
Figure A-1. Catenary Unlighted Markers A-2
Appendix A
CATENARY MARKERS - LINE SPACING Adjacent Lines Greater Than 200 ft (61 m) Away Required for transmission lines 69 kV or greater Recognizable from a minimum distance of 4,000 ft (1,219 m) Wire markers may be staggered over the catenary to enable better wind load distribution Greater Than 200 ft (61 m) 200 ft (61 m) Violation Area (Above 200 ft (61 m) AGL) 25 ft (8 m) max distance unless line design sag requirements are greater Unlighted Marker Ball Extensive catenary wires: min 36-inch- (91-cm-) diameter markers; less extensive catenary wires: 20-inch- (51-cm-) or 12-inch-
(30.48-cm-) diameter markers.
Evenly spaced along the wire at approximately 200-ft (61-m) intervals.
Unlighted markers should alternate aviation orange, white, yellow, with aviation orange markers positioned at each end.
If less than four markers (lighted or unlighted) are on the line, all markers should be aviation orange.
Catenary crossings with multiple transmission lines require additional line markers when the outside lines on the adjacent structure are more than 200-ft (61-m) from the center of the primary structure.
Figure A-2. Catenary Markers - Line Spacing (Adjacent Lines Greater Than 200 ft (61 m) Away) A-3
Appendix A
CATENARY MARKERS - LINE SPACING Adjacent Lines Within 200 ft (61 m) or Less Required for transmission lines less than 69 kV Recognizable from a minimum distance of 4,000 ft (1,219 m) Wire markers may be staggered over the catenary to enable better wind load distribution 200 ft (61 m) or Less 200 ft (61 m)
- Violation Area (Above 200 ft (61 m) AGL) 25 ft (8 m) max distance unless line design sag requirements are greater Unlighted Marker Ball Extensive catenary wires: min 36-inch- (91-cm-) diameter markers; less extensive catenary wires: 20-inch- (51-cm-) or 12-inch-
(30.48-cm-) diameter markers.
Evenly spaced along the wire at approximately 200-ft (61-m) intervals.
Unlighted markers should alternate aviation orange, white, yellow, with aviation orange markers positioned at each end.
If less than four markers (lighted or unlighted) are on the line, all markers should be aviation orange.
Catenary crossings with multiple transmission lines require additional line markers when the outside lines on the adjacent structure are more than 200-ft (61-m) from the center of the primary structure.
Figure A-3. Catenary Markers - Line Spacing (Adjacent Lines Within 200 ft (61 m) or Less A-4