How are Wind Turbines lit?
Medium-intensity lights on the nacelle, and on a wind farm, a lit outline of turbines that flash together.
A wind turbine that is judged to be an obstacle is marked, lit, or both. The lights are normally medium-intensity lights on top of the nacelle, the housing at the top of the tower. For turbines of 150 m to 315 m overall height, ICAO recommends a second light as an alternate in case the operating light fails.
A wind farm is treated as one large obstacle. The outer turbines are lit to show its extent, with a limit on the gap between lit turbines, and where flashing lights are used, the lit turbines flash together. Any turbine of significantly higher elevation inside the farm is lit as well.
For turbines from 150 m to 315 m overall height, ICAO also recommends at least three low-intensity Type E lights on the tower at half the nacelle height (flashing red, 32 cd, flashing at the same rate as the nacelle light); above 315 m an aeronautical study decides. By day, the blades, nacelle and upper two-thirds of the tower are typically marked with white paint where the regulator requires it.
| Part | Treatment | Notes |
|---|---|---|
| Nacelle | Flashing white (ICAO Type A)Flashing red (FAA) | Medium-intensity light, visible from every direction; ICAO also allows Type B (flashing red) or Type C (fixed red); alternate light on turbines of 150 m to 315 m |
| Tower | Tier lights | At least three low-intensity Type E lights (flashing red, 32 cd, at the nacelle flash rate) at half the nacelle height on turbines of 150 m to 315 m (ICAO); the FAA sets its own tier lighting |
| Blades, nacelle, tower | Marking | Typically white paint on the blades, nacelle and upper two-thirds of the tower; some regulators also require blade-tip bands |
| Wind farm | Lit outline | Outer turbines lit, with a limit on the gap; all lit turbines flash together |
Find the overall height
The overall height (hub height plus vertical blade height) decides how the turbine is lit: under 150 m, 150 m to 315 m, or over 315 m.
Light the nacelle
Fit the light on top of the nacelle so it is seen from every direction and not blocked by the blades. Add an alternate light on turbines of 150 m to 315 m; above 315 m an aeronautical study decides.
Choose which turbines
Light the outline of the farm, with a limit on the gap between lit turbines, and any turbine of significantly higher elevation. Other inner turbines may stay unlit.
Synchronise and monitor
Time the flashes together, set the intensity for day, twilight and night where the light type requires it, and monitor each light for failure.
Turbine lighting is not one fixed recipe. Three ideas are often mixed up:
- Standard Lighting→ lights flash on every night (and by day for white lights), regardless of aircraft
- Aircraft Detection Lighting→ lights switch on only when a sensor detects an aircraft nearby, where the regulator allows it
- Marking→ white paint on the blades, nacelle and upper two-thirds of the tower that makes the turbine visible by day
Also note that lighting the outline of a farm does not mean every turbine carries a light, and that flashing together is part of the requirement, not a nicety.
ICAO Wind-turbine Lighting
ICAO Annex 14 Volume I, Chapter 6, says a wind turbine that is determined to be an obstacle is to be marked, lit or both. Lighting is normally a medium-intensity light on the nacelle, placed so the turbine is visible from every direction. ICAO recommends that turbines of 150 m to 315 m overall height add a second nacelle light as an alternate and at least three low-intensity Type E lights (flashing red, 32 cd) at half the nacelle height, with low-intensity Type A or B allowed if an aeronautical study finds Type E unsuitable; above 315 m an aeronautical study decides. A wind farm is treated as an extended object: the perimeter is lit with a limit on the spacing between lights, any turbine of significantly higher elevation is also lit, and where flashing lights are used they flash together. Medium-intensity light types are flashing white (Type A), flashing red (Type B) or steady red (Type C), and the State chooses. Marking by day is typically white paint on the rotor blades, nacelle and upper two-thirds of the tower. Take the light type, number, layout and any reduced or detection-based lighting from the regulator's determination and the current edition of the standard.
FAA Wind-turbine Lighting
The FAA covers wind turbines in AC 70/7460-1, Obstruction Marking and Lighting. Its usual treatment is flashing red lights on the nacelle, fitted in pairs for redundancy, with the lit turbines of a farm flashing in step. The advisory circular sets which turbines of a farm are lit, the maximum gap between them, and tier lighting for the tallest turbines, and it also describes aircraft detection lighting systems. Confirm the current edition and what the FAA determination requires for your project.
Frequently Asked Questions
Q1How are wind turbines lit for aircraft?
Normally with a medium-intensity light on top of the nacelle, which is the housing at the top of the tower behind the rotor hub. ICAO allows a flashing white light (Type A), a flashing red light (Type B) or a steady red light (Type C), and the State decides which is used. The FAA usually uses a flashing red light. ICAO recommends that turbines of 150 m to 315 m overall height add a second nacelle light as an alternate and a tier of at least three low-intensity Type E lights (flashing red) at half the nacelle height. The rotor blades, nacelle and upper two-thirds of the tower are also painted white by day where the regulator requires.
Q2Why are the lights on the nacelle and not on the blades?
The nacelle is the housing at the top of the tower. It turns slowly to face the wind but does not spin with the rotor, and a light on top of it can be seen from every direction. The blades rotate, so they are normally marked with paint rather than lit.
Q3Does every turbine in a wind farm need a light?
Not always. The farm is treated as one large obstacle. The outer turbines are lit to show its extent, with a limit on the gap between lit turbines, and the inner turbines may be left unlit where the regulator agrees, except that any turbine of significantly higher elevation is also lit. The count and spacing are set by the regulator.
Q4Why do the lights have to flash together?
If the lit turbines flash out of step, the farm looks like a confusing field of random lights. Flashing together, usually timed from a satellite clock, makes the group read as one obstacle and is less distracting to people on the ground.
Q5Can the lights be switched off when no aircraft are near?
Some regulators allow aircraft detection lighting. A radar or similar sensor switches the lights on only when an aircraft is detected nearby. Whether it is allowed, and the approved systems, depend on the regulator.
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