IEC TS 61400-29:2023

IEC TS 61400-29 ®
Edition 1.0 2023-02
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –
Part 29: Marking and lighting of wind turbines
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IEC TS 61400-29 ®
Edition 1.0 2023-02
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –

Part 29: Marking and lighting of wind turbines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-6401-0

– 2 – IEC TS 61400-29:2023  IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Symbols and abbreviated terms . 10
4.1 Abbreviations . 10
5 Marking of a wind turbine and wind farms . 11
5.1 General . 11
5.2 Reflectance or luminance factor . 11
6 Lighting of a wind turbine and wind farms . 12
6.1 International Civil Aviation Organization requirements . 12
6.2 Planning considerations . 12
6.3 Wind turbines with a tip height less than 150 m . 13
6.4 Wind turbines with a tip height of 150 m or more . 13
6.5 Lighting of wind farms . 14
6.5.1 General . 14
6.5.2 Onshore wind farms . 16
6.5.3 Offshore wind farms. 17
6.5.4 Deconfliction with marine lighting . 18
6.6 Wind farms near aerodromes . 18
6.7 Lights specifications. 19
6.7.1 General . 19
6.7.2 Battery back-up time . 20
6.7.3 Night vision goggle compatibility . 20
6.7.4 Monitoring and control . 21
7 Considerations during construction . 21
8 Reduction of light pollution . 22
8.1 General . 22
8.2 Dimming . 22
8.2.1 Scope . 22
8.2.2 Operation . 22
8.2.3 Visible ranges . 22
8.3 Aircraft detection systems . 23
8.3.1 General . 23
8.3.2 Operation and boundaries . 23
8.3.3 Integrity monitoring . 24
Annex A (informative) Wind turbines located in areas with lengthy periods of snow . 25
Annex B (normative) Definition of colours for markings on wind turbines . 26
B.1 Specifications . 26
B.2 Provisions for practical implementation . 27
Annex C (normative) Definition of colours for wind turbine lights . 28
C.1 General . 28
C.2 Chromaticities for wind turbine lights with filament-type light sources . 28
C.3 Chromaticities for wind turbine lights with a solid state light source . 28

Annex D (normative)  Light distribution for low, medium or high intensity aviation
obstacle lights . 30

Figure 1 – Lighting configurations for wind turbines exceeding 150 m . 14
Figure 2 – Linear configuration wind farm . 15
Figure 3 – Basic layout of a linear alignment . 15
Figure 4 – Lighting configuration of an onshore wind farm . 17
Figure 5 – Lighting configuration of an offshore wind farm . 18
Figure A.1 – Wind turbines in areas with lengthy periods of snow . 25
Figure B.1 – Ordinary colours for wind turbine marking . 27
Figure C.1 – Colours for wind turbine lights with filament-type light sources . 29
Figure C.2 – Colours for wind turbine lights with solid state light sources (LED) . 29

Table 1 – Wind turbines paint colours . 11
Table 2 – Characteristics of obstacle lights . 19
Table D.1 – Light distribution for low-intensity obstacle lights . 30
Table D.2 – Light distribution for medium- and high-intensity obstacle lights according

to benchmark intensities of Table D.1 . 30

– 4 – IEC TS 61400-29:2023  IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 29: Marking and lighting of wind turbines

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 61400-29 has been prepared by IEC technical committee 88: Wind energy generation
systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
88/894/DTS 88/913/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.

A list of all parts in the IEC 61400 series, published under the general title Wind energy
generation systems, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

– 6 – IEC TS 61400-29:2023  IEC 2023
INTRODUCTION
As the Wind Industry grows, airspace users (military, civil and emergency aircraft) need to
continue to operate safely in an environment that includes wind turbines, and the two industries
need to exist harmoniously.
To assist in creating a safe environment, some wind turbines are required to have aeronautical
lights so they can be seen by airspace users. Unfortunately, some of these lights can have an
adverse visual impact, which produces lighting pollution for nearby communities.
Annex 14 to the Convention on International Civil Aviation published by the International Civil
Aviation Organization (ICAO) contains Standards and Recommended Practices (specifications)
that prescribe the marking and lighting of wind turbines. However, many countries have
interpreted these specifications differently and issued their own guidelines and conditions to
suit their local requirements. Therefore, there is little homogeneity and wind turbine
manufacturers are obliged to produce bespoke designs to suit specific markets.
There are currently approximately 20 different marking and lighting specifications for countries
such as Belgium, Brazil, Canada, Finland, France, Germany and Japan. In many cases, those
requirements are very similar. However, they often differ in terms of light intensity, positioning
and markings, which could lead to confusion and reduction in air safety.
In some cases wind farms that are separated by only a few kilometers are marked and
illuminated in accordance with different guidelines. This includes the transition from the onshore
to the offshore wind environment, and vice versa.
This document reflects the need to allow the coexistence of wind turbines and aviation, ensuring
that the ICAO Standards and Recommended Practices are followed but also balances with the
environmental impact on nearby residents.
References to national regulations are important in this document, given the regional specific
circumstances required in many cases. Users should be aware that national and/or "local"
regulations can apply. The aim is to encourage safe airspace but with minimum light pollution.
NOTE Throughout the drafting process for this document, the National Guidelines, related to lighting and marking
wind turbines, of many ICAO Member States have been used as a resource. However, the guidance documents are
too numerous to list and, therefore, reference to any non-normative documents has been omitted.

WIND ENERGY GENERATION SYSTEMS –

Part 29: Marking and lighting of wind turbines

1 Scope
This part of IEC 61400, which is a Technical Specification, instils good practice for aviation
lighting and marking of wind turbines in both onshore and offshore domains. Consideration is
given to visible lighting and infrared (IR) lighting, which is necessary to maintain conspicuity to
users of night vision goggles (NVGs).
ICAO Annex 14 Standards and Recommended Practices have been used as the basis to
develop supplementary harmonised specifications to assist with implementation.
This document provides a set of technical requirements for marking and lighting of wind turbines
with a tip height from/at 150 meters and below 315 meters Above Ground Level (AGL), or Above
Mean Sea Level (AMSL) for offshore sites. This will improve situational awareness for airspace
users, maintain safety of aircraft flying in the vicinity of wind turbines, and provide additional
tools to assist with the reduction in environmental impacts consistent with aviation safety
objectives. In the event that the wind turbine development exceeds 315 m tip height and the
regulatory frameworks is updated to cater for these heights, this document will be reviewed and
amended as necessary. In the absence of an update to the regulatory framework, the guidance
in this document is to be followed as a minimum.
In some cases, lighting may be required for wind turbines at or below 150 meters tip height.
However, this is not in the scope of this document and in these situations, the developer should
contact the relevant National Aviation Authority or Planning Authority for further guidance.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61400-3-1:2019, Wind energy generation systems - Part 3-1: Design requirements for fixed
offshore wind turbines
IEC 62443-4-2:2019, Security for industrial automation and control systems - Part 4-2:
Technical security requirements for IACS components
International Civil Aviation Organization, Annex 14, Aerodromes – Volume I – Aerodromes
th
Design and Operations. 8 Edition, July 2018
International Civil Aviation Organization, Aerodrome Design Manual – Part 4 – Visual Aids
th
(Doc 9157 – Part 4). 5 Edition. 2021
European Union Aviation Safety Agency (EASA), Certification Specifications and Guidance
Material for Aerodromes Design CS-ADR-DSN, Issue 5, June 2021
Federal Aviation Administration. Advisory Circular 150/5345-43J – Specification for Obstruction
Lighting Equipment, 11 March 2019

– 8 – IEC TS 61400-29:2023  IEC 2023
Federal Aviation Administration. 70/7460-1M – Obstruction Marking and Lighting, 16 November
IALA Recommendation R0139 (O-139) ,The Marking of Man-Made Offshore Structures, Edition
3.0, December 2021
NOTE Although too many to list explicitly, in drafting this document the national guidelines of many ICAO Member
States, for lighting and marking wind turbines, have been given due consideration. In some cases, specific examples
have been provided from national guidelines to enhance the international guidance in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
aerodrome
defined area (including any buildings, installations and equipment) intended to be used either
wholly or in part for the arrival, departure and surface movement of aircraft
3.2
aviation Obstacle Lights
warning lights (visual and infrared) used to reduce hazards to aircraft by indicating the presence
of the obstacles
3.3
aviation Obstacle Markings
warning markings used to reduce hazards to aircraft by indicating the presence of the
obstacles
3.4
candela
International System of Units (SI) base unit of luminous intensity that denotes the luminous
power per unit solid angle emitted by a point light source in a particular direction
3.5
cluster configuration wind farm
wind turbines arranged in a non-linear configuration (see 3.10)
3.6
daytime light
period(s) of the day when the background luminance is above 500 cd/m
3.7
effective luminous intensity
effective luminous intensity of a flashing light is equal to the intensity of a steady-burning (fixed)
light of the same colour which produces the same visual range under identical conditions of
observation
3.8
grid configuration wind farm
wind turbines arranged in a geographical shape such as a square or a rectangle, with each
turbine placed a consistent distance apart in rows
3.9
LED technology
light emitting diode (LED) is a semiconductor light source that emits light if electrical current
flows through it
Note 1 to entry: It can emit visible, IR or ultraviolet radiation depending on the semiconductor material and the
doping wavelength. LEDs are energy efficient and have a long lifespan.
3.10
linear configuration wind farm
wind turbines arranged in linear configuration are placed in a row along a ridgeline, the face of
a mountain, or along the borders of a hill or field
Note 1 to entry: The line may be ragged in shape or be periodically broken.
3.11
luminance
luminous intensity per unit emitting area. It is a photometric quantity which may be applied to
light sources but also to light which is reflected or passes through a particular area
Note 1 to entry: Its unit is 'Candela per Square Meter' (cd/m ).
3.12
nanometer
unit of length in the metric system, equal to one billionth of a meter
Note 1 to entry: The international unit for nanometer, nm is 10^(-9) m.
3.13
nautical mile
unit of measurement used in both air and marine navigation
Note 1 to entry: The international nautical mile is exactly 1 852 meters.
3.14
night-time light
period(s) of the day when the background luminance is below 50 cd/m
3.15
night vision goggles
helmet mounted night vision enhancement aid that utilises image intensifier technology and is
sensitive to light wavelengths between 660 and 920 nanometers
3.16
obstacle
fixed (whether temporary or permanent) and mobile objects, or parts thereof, that:
a) are located on an area intended for the surface movement of aircraft; or
b) extend above a defined surface intended to protect aircraft in flight; or
c) stand outside those defined surfaces assessed as being a hazard to air navigation
3.17
offshore wind turbine
wind turbine that converts kinetic energy in the wind into electrical energy and has a sub-
structure that is subject to hydrodynamic loading and is founded on the seabed, including
floating structures
3.18
onshore wind turbine
wind turbine that converts kinetic energy in the wind into electrical energy located on a land
mass
– 10 – IEC TS 61400-29:2023  IEC 2023
3.19
tip height of a wind turbine
maximum height AGL (onshore) and AMSL (offshore), of the tip of the turbine blades at their
highest point
3.20
twilight-time light
light during the period(s) of the day when the background luminance is between 50 and
500 cd/m
3.21
visibility
aeronautical visibility is the greater of:
a) the greatest distance at which a black object of suitable dimensions, situated near the
ground, can be seen and recognised when observed against a bright background,
represented by the meteorological optical range (MOR)
b) the greatest distance at which lights in the vicinity of 1000 candelas (cd) can be seen and
identified against an unlit background, which varies with the background illumination
3.22
wind farm
group of two or more wind turbines in the same geographical area, used to produce electricity
3.23
wind turbine
structure intended for the production of electrical power; comprising a support tower, a nacelle,
a generator unit, and rotor blades that are caused to rotate by the wind
4 Symbols and abbreviated terms
4.1 Abbreviations
ADS aircraft detection system
AGL above ground level
AIP Aeronautical Information Publication
AMSL above mean sea level
cd candela
CIE International Commission on Illumination
EASA European Union Aviation Safety Agency
FAA Federal Aviation Administration
fpm flashes per minute
IALA International Association of Lighthouse Authorities
ICAO International Civil Aviation Organization
IEC International Electrotechnical Commission
IR infrared
ISO International Organization for Standardization
JORF Journal officiel de la République française (Official Journal of the French Republic)
LED light emitting diode
MOR meteorological optical range
NM nautical mile
NOTAM notice to airmen
NVG night vision goggles
PAS Publicly Available Specifications
RAL Reichs-Ausschuß für Lieferbedingungen und Gütesicherung (Imperial Commission
for Delivery Terms and Quality Assurance)
SARPs Standards and Recommended Practices
SI International System of Units
TS Technical Specification
UK United Kingdom
USA United States of America
UTC coordinated universal time
VFR visual flight rules
5 Marking of a wind turbine and wind farms
5.1 General
ICAO recommends rotor blades, nacelle and upper 2/3 of the supporting tower of all wind
turbines be painted white. Due to a number of factors, including gaining planning permission,
grey is the generally accepted colour choice for onshore turbines, to enhance conspicuity.
Colours are based on colorimetric quantities and luminance factor.
This document only recommends the use of colour bands in geographic areas that have lengthy
periods of snow cover, such as Alaska or Nordic countries, and where it is deemed necessary,
the rotor blades and the tower of the turbine may have a band of Traffic Red as given in Annex A
to provide additional contrast against the snow in accordance with national requirements.
In the offshore environment, if there are railings on the nacelle for a helicopter winch area, it is
recommended that the railings are painted a conspicuous colour, preferably red, in accordance
with IEC 61400-30, Safety of Wind Turbine Generator Systems – General principles for design.
Should railings be installed, the 360° visibility of the light must be maintained.
5.2 Reflectance or luminance factor
The luminance factor of grey colours shall be greater than or equal to 0,4. The luminance factor
of white colours is to be greater than or equal to 0,6.
Table 1 shows a list of the most commonly white and grey colours used on wind turbines. Any
other colour may be used as long as it complies with the above mentioned requirements of
luminance factor.
Table 1 – Wind turbines paint colours
Luminance
Name RAL
Factor (ß)
Grey white 9002 0,68
Signal white 9003 0,84
Pure white 9010 0,85
Traffic white 9016 0,85
Papyrus white 9018 0,61
Light grey 7035 0,56
Agate grey 7038 0,43
Telegrey 4 7047 0,57
– 12 – IEC TS 61400-29:2023  IEC 2023
The specifications of surface colours given above are described in Annex B.
6 Lighting of a wind turbine and wind farms
6.1 International Civil Aviation Organization requirements
There are over 190 countries that are signatories to the Chicago Convention of 1947, which
established the International Civil Aviation Organization. Article 12 of the Convention requires
Member States to keep their own regulations uniform “to the greatest possible extent” with the
Standards and Recommended Practices (SARPs) promulgated by ICAO. Under Article 37,
States are obliged to “collaborate in securing the highest practicable degree of uniformity” in
their domestic law, regulations and procedures with their domestic law, regulations and
procedures with SARPs.
ICAO Annex 14, paragraph 6.2.4.1, which is a standard, states that:
• “A wind turbine shall be marked and/or lighted if it is determined to be an obstacle.”
This is supported by a reference to paragraph 4.3.2, which notes that:
• “in areas beyond the limits of the obstacle limitation surfaces [of aerodromes], at least those
objects which extend to a height of 150 m or more above ground elevation should be
regarded as obstacles, unless a special aeronautical study indicates that they do not
constitute a hazard to aeroplanes.”
The application of lighting requirements specified in this document is to ensure that an obstacle
to air navigation remains visible and supporting standardisation in accordance with ICAO
SARPs.
6.2 Planning considerations
Prior to submitting an application to the local planning authority to request approval to construct
a wind turbine or wind farm, the applicant shall inform the local civil aviation authorities of their
intention to develop or build a wind turbine or wind farm.
To achieve this, aviation obstacle lights might be installed on the top of the nacelle. Additionally,
it may also have a level of obstacle lights around the tower, depending on the total height of
the wind turbine.
It is a requirement that a 360° lighting coverage in the horizontal plane is accomplished, as
viewed from an aircrew perspective when approaching from all directions. To achieve this
requirement the number of physical light sources shall be minimised. By employing the lowest
number of light sources the environmental impact is reduced in all situations. Consideration to
maximising each lighting unit's beam angle should be given to achieve this 360° view, whilst
keeping the number of light units as low as possible.
In considering the 360° lighting requirement, it is acknowledged that each individual turbine will
not be able to meet this continuously when viewed from any direction. This is due to obscuration
caused by its own blades and adjacent turbines. It is not possible to specify a minimum number
of lights but it is essential that any proposed lighting scheme ensures the windfarm is lit
contiguously so that it can be seen from any angle.
Wind turbines can create hazards for a number of reasons, however, only the specific physical
impact on aviation that requires aviation lighting is dealt with in this document. Other risks and
hazards associated with wind turbines are addressed in IEC TS 61400-31, Wind energy
generation systems – Part 31: Siting Risk Assessment.

6.3 Wind turbines with a tip height less than 150 m
Wind turbines with a total height of less than 150 m are not considered an obstacle in this
document. Therefore, they do not need to be equipped with aviation obstacle lights, either on
the top of the nacelle or on the tower, unless otherwise indicated by an aeronautical study or
requested by an aviation authority.
If night lighting is installed, wind turbines should be equipped with medium-intensity Type B or
C lights on the top of the nacelle as described in 6.7.
If two lights are installed, the lights should be mounted on the top of the nacelle and arranged
horizontally with enough separation to ensure an unobstructed view of at least one light by an
aircraft approaching from any direction.
6.4 Wind turbines with a tip height of 150 m or more
Wind turbines from/at 150 m to 315 m in overall height shall be equipped as described below.
However, the aviation lights on one or more wind turbines within a wind farm can be omitted as
described in 6.5.
– At night, red medium-intensity Type B or C lights according to 6.7 shall be mounted on the
top of the nacelle and arranged horizontally with enough separation to ensure an
unobstructed view of at least one light by an aircraft approaching from any direction.
– If daytime lighting is installed, white medium-intensity Type A lights according to 6.7 shall
be mounted on the top of the nacelle and arranged horizontally with enough separation to
ensure an unobstructed view of at least one light by an aircraft approaching from any
direction. Alternately, high-intensity Type A or B lights might be required by aviation
authorities under certain circumstances.
– If tower lights are installed, one level of low-intensity Type B lights according to 6.7 shall be
placed at a point midway between the top of the nacelle and ground level. The location shall
have a vertical tolerance of +/-20 m subject to national authority approval. Consideration
should be given to locating the lights to be below the lowest pass point of the rotor blades
to minimise flicker effects but remaining within the +/- 20 m tolerance. The lights shall be
arranged horizontally with enough separation to ensure a 360° unobstructed view of at least
one light by an aircraft approaching from any direction. Due to factors such as effectiveness
and acceptance, flashing lights are not recommended.
The lighting requirement configurations are illustrated in Figure 1.

– 14 – IEC TS 61400-29:2023  IEC 2023

Figure 1 – Lighting configurations for wind turbines exceeding 150 m
6.5 Lighting of wind farms
6.5.1 General
The aviation lights on one or more wind turbines within a wind farm can be omitted, depending
on the terrain features, geographic location and the overall layout of the wind farm.
As a general rule, the maximum distance between lit turbines shall be no more than 900 m for
onshore wind turbines and no more than 1 800 m (1 nautical mile (NM)) for offshore wind
turbines. This is in accordance with ICAO Annex 14 for onshore but it is noted that as wind
turbine sizes increase with a subsequent impact on spacing between individual turbines, the
need to balance aviation safety requirements with environmental lighting impact will become
more challenging. Consequently, there may be a need for wind farm developers to engage with
national authorities to develop a safety case to support greater spacing. In addition, national
authorities may be requested to refer this to the appropriate ICAO working group for further
consideration.
As shown in Figure 2, the wind turbines at each end of the line as well as any breakage or
change of direction should be fitted with aviation lights.

Figure 2 – Linear configuration wind farm
To determine the periphery of a wind farm, three successive wind turbines are considered to
be aligned if the intermediate wind turbine is located at a distance equal or less than 200 m
from the line segment connecting the two outer wind turbines. Due to a number of variables,
e.g. topography, it may not be possible to apply this rule absolutely in all cases and some
variation to this calculation may be required. Further discussion with the aviation and planning
authorities may be needed.
A basic layout of linear alignment of wind turbines is shown in Figure 3. It applies for both
onshore and offshore. The values for an offshore alignment are in brackets and written in blue.

Figure 3 – Basic layout of a linear alignment
ICAO Annex 14 specifies lighting at longitudinal intervals not exceeding 900 m. However, it is
stated in respect of wind turbines that the maximum spacing between the lights along the
perimeter should be respected unless a dedicated assessment shows that a greater spacing
can be used. While the 900 m requirement is particularly relevant to onshore wind turbines,
especially given the turbine size at the time the text was drafted, offshore turbines have
significantly increased in height. Consequently the spacing between turbines has increased to
ensure efficient operation. This, in conjunction with increased spacing to allow for helicopter
access, means that individual turbine spacing generally exceeds 900 m by a significant margin.
Consequently, there has been a realistic approach by some administrations to consider an
increased spacing of 1 800 m in the offshore environment as long as it does not present an
increased safety risk. As this approach is not inconsistent with ICAO Annex 14, developers are
advised to consult with the relevant National Aviation Authority to gain approval for their lighting
proposals.
Methods for minimizing the visual impact of offshore and onshore wind farm are described in
Clause 8.
– 16 – IEC TS 61400-29:2023  IEC 2023
For grid configuration: Wind turbines on the corners should be fitted with aviation lights, and
then use the same concept described in 6.5.2 to ensure there is no gap exceeding 900 m without
unlit turbines.
For cluster configuration: A turbine from the outer perimeter of the farm needs to be lit and
selected as starting point, the next wind turbine along the outer perimeter is lighted assuring
that there is no space of more than 900 m without unlit turbines. This pattern should be
continued 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 across distance of the wind farm is greater than 1 800 m, the most central wind
turbines should be fitted with aviation lights as described in 6.5.2 and 6.5.3.
6.5.2 Onshore wind farms
If the farm layout is configured in a non-linear arrangement, like a grid or a cluster configuration,
the following steps should be applied in the order as shown in 1) to 4). The lighting configuration
should apply to both night and day lighting:
1) The corners and the periphery of the wind turbine farm are to be lit, the maximum distance
between lit turbines shall be no more than 900 m in order that the outline of the windfarm
can be clearly delineated by aviators;
2) If the tip height of any wind turbine that is significantly higher in elevation than other wind
turbines in close proximity, that turbine should be lit independently of its position. In making
the assessment to identify which turbines need to be lit in this scenario, the topography and
lateral separation of the individual turbines will need to be assessed on a specific site basis.
However, as guidance, if the height of other turbine nacelle(s) in the wind farm exceed the
height of a plane extending at an elevation of 10° above the horizontal from the nacelle of
a turbine that is required to be lit, then obstacle lighting must be fitted and operated on the
identified wind turbine. The 10° value is based on a practical assessment and may need to
be adjusted to meet local circumstances based on the advice of regulatory authorities. It
should also be noted that this approach may not meet the requirements in every terrain
circumstance and an alternative approach of setting a criteria of lighting any additional
turbine which has a significant height difference, e.g. > 20 m agl, from those that are lit
could be used as an alternative means of assessment;
3) Any wind turbine that is located at a distance greater than 900 m from the nearest marked
wind turbine should be also lit;
4) To avoid any potential light pollution, a distinction can be made, if agreed with the national
regulatory authorities. An example of this is to tilt the aviation light beam angle upwards
between 0° and 3° to the horizontal plane, dependant on turbine height;
5) Any wind turbine inside the cluster of wind turbines located at a distance greater than
1 800 m (1 NM) from the nearest marked wind turbine must be also lit unless there are
significant discrepancies in elevations referred to in 2) above.
Additionally, if some turbines are located apart from the main group, i.e. if one or more turbines
protrude from the general limits of the wind farm, they should also be lit.
Figure 4 shows the night-time lighting configuration of an onshore wind farm. However, the
steps mentioned in 1) to 4) should apply to daytime lighting as well.

Figure 4 – Lighting configuration of an onshore wind farm
6.5.3 Offshore wind farms
The following steps should be applied in the order as shown below for the lighting configuration
of offshore wind farms on the basis that the turbines are of equal height:
1) The periphery (corners) of the wind turbine farm is to be lit, the maximum distance between
lit turbines shall be no more than 1 800 m (1 NM). However, in accordance with the note in
6.5, this may need to be updated as wind turbine sizes increase.
2) Any wind turbine inside the cluster of wind turbines located at a distance greater than
3 600 m (2 NM) from the nearest marked wind turbine must be also lit.
Figure 5 shows a night-time lighting configuration of an offshore wind farm. However, the steps
mentioned in 1) and 2) should apply to day lighting as well.

– 18 – IEC TS 61400-29:2023  IEC 2023

Figure 5 – Lighting configuration of an offshore wind farm
6.5.4 Deconfliction with marine lighting
To avoid any potential confusion between maritime and aeronautical lighting of objects, there
are a number of distinctions that can be made, if agreed with the national regulatory authorities.
Two examples of this are:
• Tilting the aviation light beam angle upwards between 0° and 3° to the horizontal plane, to
avoid confusion with marine lights and reduce light pollution
• Using a flashing Morse Code 'W' light on the turbine hub as used in United Kingdom (UK)
waters
The scope of this document only covers lighting of wind farms in the aeronautical domain.
However, it is important to be aware of the International Association of Lighthouse Authorities
(IALA) document, 'The Marking of Man-made Offshore Structures', which follows a similar
approach to lighting obstacles to this document in the marine domain.
6.6 Wind farms near aerodromes
All wind turbines in the vicinity of any aerodro
...