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Objects Affecting Airspace


Any communications structure, building or other structure, whether temporary or permanent, which has the potential to endanger aviation in navigable airspace, or has the potential to interfere with the operation of navigation or surveillance systems or Instrument Landing Systems, including meteorological systems for aeronautical purposes, is considered an OBSTACLE and shall be submitted to the Commissioner for Civil Aviation for evaluation (refer SA-CAR Part 139.01.33) 

Also applicable is Part 91.01.10 of the CAR of 1997 - endangering safety:

"No person shall, through any act or omission endanger the safety of an aircraft or person therein, or cause or permit an aircraft to endanger the safety of any person or property". 

Part 185.00.1(1) (f) makes non-compliance with the above-mentioned Regulation an offence.  

As navigable airspace is any airspace where "heavier than air" craft can operate, it means that any obstacle, anywhere, needs to be evaluated. 


The main reason is to control or prevent structures that could have a serious effect on aviation safety, especially in the vicinity of an aerodrome. (An aerodrome is a defined area on land or water intended for the arrival, departure and surface movement of aircraft – ICAO definition). It also follows that the knowledge of where obstacles are, will add to aviation safety. 

A database of all obstacles is kept and those above 60m above ground level are published in an Aeronautical Information Circular (AIC) and indicated on aeronautical maps. This data is also made available for other purposes such as for use on the onboard computers of some aircraft, for environmental research purposes etc. 

Does my structure require lights or any other markings? 

Obstacles are evaluated individually and marking (If any) are specified as requirements. 

The following syntax are used:

  1. None: There are no requirements as far as the marking of the structure is concerned and may be left as is, camouflaged as a pink elephant, a tree, signpost etc.
  2. Night Markings: Night markings are the addition of lights at the highest practical point of a structure to make such a structure more visible in darkness and poor light conditions. This will be found mostly on communications structures below 45m in height above ground where the need is identified to improve its visibility. The lights on top of these structures are ALWAYS used in pairs, for redundancy purposes, and shall be approved steady burning, red aeronautical obstruction lights of at least 10 candela, unless specified differently. Night markings may also be applied to buildings or other substantial structures, which by its size and appearance cannot be overlooked in normal visibility conditions, such as a skyscraper, the cooling towers of a power station, mine headgear etc. but the need is identified to improve its visibility at night and poor visibility conditions. Such structures shall be illuminated by aeronautical obstruction lights, as above, clearly defining the outline of the structure in accordance with ICAO Annex 14 chapter 6, unless specified differently. Where this is not achievable due to practical considerations, different means of compliance may be specified or allowed, after investigation. This may be in the form of flood lighting, effect lighting (such as illuminated advertisements) etc.
  3. Day and Night Markings:- 

    Day and night markings apply to all structures exceeding 45m above the ground in South Africa by default (refer SA-CAR Part 139.01.33), or lower structures when specified. Such structures may include structures where the top of the structure exceeds 150m above the MEAN ground level, like on top of a hill, and the mean ground level considered to be the lowest point in a 3 Kilometre radius around such structure. Lower structures, which are otherwise considered as a danger to aviation, shall also be marked as such when specified.  

    Paint markings (Day markings) shall be in compliance with ICAO Annex 14 chapter 6 and shall consist of seven painted bands, each one seventh of the length of the structure, and shall consist of bands of International Orange (or Post Office red) alternated by brilliant white, starting and ending in orange/red, to a maximum length of 30 metres per band (i.e. a 210m mast). Thereafter it becomes 9 bands, each one ninth of the length of the mast up to 270m, 11 bands up to 330m etc.  

    Lights (Night marking) to be used shall consist of a pair of steady burning approved red aeronautical obstruction lights of at least 32 candela each at the highest practical point of the structure. This may be substituted by a medium intensity Type B flashing red light (20 – 60 flashes per minute), of 2000 candela (±25 %) intensity in accordance with ICAO Annex 14 table 6-3. 

    Intermediate lights shall be placed at a position midway between the top of the structure and the ground and shall consist of at least three steady burning red aeronautical obstruction lights of at least 32 candela each, on the same vertical plane and spaced not more than 120 degree horizontally. At least two lights shall be visible through any azimuth of 360 degree and no light shall be spaced more than 30m apart, on the horizontal plane of any structure. Multiple lights may be required to satisfy this requirement. The vertical spacing of lights shall be as far as practical be evenly spaced and shall not exceed 45m between vertical levels.      


  1. Structures of 45 to 90m heights shall have dual lights on top and not less than a set of three lights at the intermediate level. An additional set of lights shall be added when the structure exceeds 90m in height and for any multiple thereafter.
  2. On structures of more than 90m,the top and every odd numbered light below may be substituted by a medium intensity Type B flashing red light (20 – 60 flashes per minute), of 2000 candela (±25 %) intensity in accordance with ICAO Annex 14 table 6-3.
  3. These flashing lights shall be synchronised.

The Commissioner may require more stringent markings in specific situations and may require that lights be powered from a no-break power source (UPS).

What about power lines?

Power lines, overhead wires and cables are considered as obstacles and the detail shall be communicated to the Commissioner at an early planning stage.

The Commissioner shall require the route of the power line, the co-ordinates (latitude and longitude in degree, minute, seconds and tenth of seconds format) of turning points in the line, the maximum height of the structures above ground level and the name of the power line. The Commissioner shall evaluate the route and require those sections of the line (if any), which is considered a danger to aviation to be marked or rerouted.

Power lines shall be marked when crossing a river, valley or major highway with marker spheres of a diameter of not less than 60 cm. The spheres shall be of one colour and displayed alternately orange/red and white or a colour that is in sharp contrast to the background as seen from an airborne perspective. The spacing between the spheres and between the spheres and the supporting towers shall not exceed 30m. On lines with multiple cables, the spheres shall be fitted to the highest cable.

The marker spheres shall be visible from at least 1000m from an airborne perspective and 300m from the ground.

Where power lines crosses a river or valley, the co-ordinates (latitude and longitude in degree, minute, seconds and tenth of seconds format) and the height of the line above the valley or river, shall be communicated to the Commissioner for publication in the appropriate media.

The Commissioner may require that supporting towers be marked and lighted.


Where cranes are erected, prior permission shall be obtained from the Commissioner. The co-ordinates (latitude and longitude in degree, minute, seconds and tenth of seconds format), the ground elevation of the site above sea level, the height of the crane, the dimensions of the jib as well as the erecting date and duration of the project must be communicated to the Commissioner for evaluation and publication in the relevant media.

The Commissioner shall specify markings, if required.

When markings are required, the crane shall be painted in a conspicuous colour which in a sharp contrast to the background from an airborne perspective. Illumination shall clearly define the shape of the crane and the extremities of the structure shall be illuminated by medium intensity Type B flashing red light (20 – 60 flashes per minute), of 2000 candela (±25 %) intensity in accordance with ICAO Annex 14 table 6-3.

Variations on Markings

Written, motivated request for the variation of any of the requirements for the marking of structures may be addressed to the Commissioner.

Where do I find the specifications on markings?

Specification on the lighting and painting of structures can be found in ICAO Annex 14 chapter 6 and the specifics in Annex 14 APPENDIX 1. COLOURS FOR AERONAUTICAL GROUND LIGHTS, MARKINGS, SIGNS AND PANELS

Is there a cost involved?

An assessment fee is applicable per application and is a "once off" providing none of the specified dimensions changed. When the height or the position of an "obstacle" has changed, it is considered as a new application. The fee is published in part 187.00.21 (Fees relating to Part 139) and is available on the CAA website under "Fees"

How Long does it Take?

Unless further investigation is required, one could expect an answer within 3 months after submission and payment of a request.

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