Please also refer to our webpage giving an overview of the requirements and notification processes for obstacles in UK airspace.
Aviation legislation relating to lighting/marking of obstacles
Persons in charge of structures must comply with applicable legislation in relation to lighting and marking to ensure that the obstacles are sufficiently visible to airspace users.
In the UK, the need for aircraft warning lighting/marking on tall structures depends in the first instance upon any structure’s location in relation to an aerodrome.
Obstacles in the vicinity of aerodromes
- Safeguarding zones/assessments of potential obstacles relating to UK civil licensed aerodromes may extend out to distances greater than 15 kilometres from the runway thresholds. Various factors (including runway lengths/configurations and the types of operation) influence the dimensions of each aerodrome’s safeguarding zones.
- If the structure constitutes an 'aerodrome obstacle', it is the aerodrome licence holder/operator that will assess the potential lighting and marking requirement. Please refer to Chapter 4 (The assessment and treatment of obstacles) of CAP 168: Licensing of Aerodromes for further details. Civil Aviation Authority (CAA) Airspace Regulation can provide details of the safeguarding points of contact at individual aerodromes.
Obstacles not in the vicinity of aerodromes
- For obstacles that are not in the vicinity of a licensed aerodrome, Article 222 of the Air Navigation Order (ANO) 2016 (as amended) requires that lighting only becomes legally mandated for structures of a height of 150 metres (m) / 492.1 feet (ft) Above Ground Level or more. This legislation requires that:
- Medium intensity (typically 2000 candela), steady (as opposed to flashing) red lights be mounted as close as possible to the top of the structure and at intermediate levels spaced so far as practicable equally between the top lights and ground level at intervals not exceeding 52 m.
- The lighting must be displayed at night and arranged so as to be visible from all directions.
- The above legislation includes provision for the CAA to specify additional lights for particular structures and issue permissions for variance from the requirements in certain cases.
Obstacle lighting/marking recommendations
Engagement with aviation stakeholders
- Outwith the legal requirements detailed on this webpage, any aviation stakeholder may consider a particular structure to be a significant navigational hazard and could make a case for it to be lit (and/or marked) for aviation purposes to increase its visibility.
- Any such request (as opposed to mandate) would need to be negotiated with the owner/developer of the structure. If asked for comment, it is unlikely that the CAA would have any fundamental issue associated with an appropriate aviation stakeholder’s case for lighting/marking of any structure that could reasonably be considered to be a significant hazard.
- In respect of any aerodrome-specific safeguarding issues, it is the aerodrome operators/licensees that hold associated safeguarding responsibility and it is for them to provide the relevant parties with what the CAA acknowledges to be expert aerodrome-specific comment on obstacle visibility.
- Due to the unique nature of operations in respect of low altitudes and potentially unusual landing sites, it is strongly recommended that the related viewpoints of local emergency services Air Support Units should be established as follows:
- locations in England and Wales – National Police Air Service
- locations in Scotland – Police Scotland Air Unit
- locations in Northern Ireland - Police Service of Northern Ireland Air Support Unit
- all UK locations - the relevant Air Ambulance Unit/s via the Air Ambulances UK organisation (please request that your message is forwarded to the appropriate Unit/s)
- To ensure that military aircraft safety is taken into consideration, the viewpoint of the Safeguarding Department within the Defence Infrastructure Organisation should be sought.
- If there is the potential for aviation offshore (or close to offshore) to be affected (particularly Search and Rescue helicopter safety), seek comment from the Aviation Team within the Maritime and Coastguard Agency (Tel: 023 8032 9416 or 023 8032 9486).
- The viewpoints of any other known sites of regular aviation activity (such as parachuting, gliding and microlight flying locations) in the vicinity should also be considered. CAA Airspace Regulation is usually able to provide details of relevant known sites.
Additional daytime markings
For certain types of structures (such as masts), additional measures may be requested by aviation stakeholders to increase the visibility of a structure during daylight periods. The General Aviation Awareness Council (on behalf of other General Aviation representative bodies) and several helicopter operators, have asked that the following guidance regarding daytime markings is relayed to owners/planners/developers by the CAA on their behalf:
- ‘Masts and / or their guy wires should be equipped with aids to increase their daytime visual conspicuity where a risk-based proposal demonstrating specific need for such measures has been submitted by the aviation stakeholder. Noting that the deployment of any such measure can only be mandated by the relevant Planning Authority, it is acknowledged that such visual conspicuity aids should not impact upon the integrity of the structure itself, the data generated or risk to personnel. These aspects are for the developer to consider / assess.
- The most effective means of achieving this may be the use of orange marker buoys on the guy wires, such as those that may be fitted to overhead power cables (the use of which has some basis in international regulatory direction). However, it is noted that in some locations the structural loads imposed by such markers may be unacceptable. In such cases, the goal of increasing the visual conspicuity of masts and supporting guys might be achieved by different means, which generally place little or no additional structural load on the mast / guy combination. Such means include:
- Painting all or part of the mast; options could include alternate contrasting stripes, such as orange and white, or a single contrasting colour (noting that it may need to contrast with terrain, or sky, or both) and / or,
- Reflective bird flight deflectors of minimum 120 mm diameter fitted to the guy wires at intervals, and / or,
- High visibility sheaths enveloping the supporting guy and / or,
- Ground mats, or construction such as a box of a contrasting colour scheme to the ground at the foot of the mast.
Whichever method is chosen, it will need to satisfy all other relevant planning considerations. For example, bird deflectors may be required for bird protection reasons, and visual intrusion concerns may need to be considered. It is envisaged that the norm would be that one method would suffice.’
In addition to the legally mandated lighting requirements detailed on this webpage, CAA guidance on the periods of illumination of obstacle lighting is given in Chapter 4 (The assessment and treatment of obstacles) of CAP 168: Licensing of Aerodromes, specifically paragraphs 4.120 and 4.121, which are reproduced below:
- ‘4.120 High intensity flashing white obstacle lights should be lit at all times throughout the day and night.’
- ‘4.121 Steady red medium and low intensity obstacle lights should be lit:
- on and adjacent to an aerodrome from 30 minutes before sunset to 30 minutes after sunrise during the hours of availability notified in the UK AIP or by NOTAM;
- on en route obstacles from 30 minutes before sunset to 30 minutes after sunrise. Should switching present problems, these lights may remain lit continuously.’
Specific CAA guidance for crane lighting/marking is given in CAP 1096: Guidance to crane users on the crane notification process and obstacle lighting and marking and on our Crane notification webpage.
Lighting/marking requirements and recommendations for wind turbines are detailed in CAP 764: Policy and Guidelines on Wind Turbines.
If you have any questions, please contact Airspace Regulation between the hours of 08:30 and 16:30 Monday to Friday (excluding Public Holidays). It may not be possible to action messages/notifications submitted after 16:00 until the next working day.
Planned periods of extended closure of the Airspace Regulation section will be notified here: