ICAO - Lighting of objects with a height 150 m or more above ground level

Recommendation.— High-intensity obstacle lights, Type A, should be used to indicate the presence of an
object if its height above the level of the surrounding ground exceeds 150 m and an aeronautical study indicates such lights to be essential for the recognition of the object by day.

 Where high-intensity obstacle lights, Type A, are used, they shall be spaced at uniform intervals not exceeding
105 m between the ground level and the top light(s), except that where an object to be marked is surrounded by buildings, the elevation of the tops of the buildings may be used as the equivalent of the ground level when
determining the number of light levels.

Recommendation.— Where, in the opinion of the appropriate authority, the use of high-intensity obstacle
lights, Type A, at night may dazzle pilots in the vicinity of an aerodrome (within approximately 10 000 m radius) or cause significant environmental concerns, medium-intensity obstacle lights, Type C, should be used alone, whereas mediumintensity obstacle lights, Type B, should be used either alone or in combination with low-intensity obstacle lights, Type B.

Where an object is indicated by medium-intensity obstacle lights, Type A, additional lights shall be provided
at intermediate levels. These additional intermediate lights shall be spaced as equally as practicable, between the top lights and ground level or the level of tops of nearby buildings, as appropriate, with the spacing not exceeding 105 m.

 Where an object is indicated by medium-intensity obstacle lights, Type B, additional lights shall be provided
at intermediate levels. These additional intermediate lights shall be alternately low-intensity obstacle lights, Type B, and medium-intensity obstacle lights, Type B, and shall be spaced as equally as practicable between the top lights and ground level or the level of tops of nearby buildings, as appropriate, with the spacing not exceeding 52 m.

 Where an object is indicated by medium-intensity obstacle lights, Type C, additional lights shall be provided
at intermediate levels. These additional intermediate lights shall be spaced as equally as practicable, between the top lights and ground level or the level of tops of nearby buildings, as appropriate, with the spacing not exceeding 52 m.