Obstacle Marking and Aerodrome Services

22.1Obstacles. The marking and/or lighting of obstacles is intended to reduce hazards to aircraft by indicating the presence of obstacles. It does not necessarily reduce operating limitations which may be imposed by obstacles. The responsibility for marking/lighting of obstacles on or near aerodromes must be determined between the aerodrome licensee and the owners of the structures. Licensees are responsible for the marking and lighting of all obstacles on the movement area irrespective of ownership. During the establishment of instrument approach and departure procedures, obstacles are identified to allow the calculation of operating minima and obstacle clearance height/altitude. The treatment of obstacles in this chapter is concerned with the identification and marking of obstacles on and in the vicinity of aerodromes, which may be collision hazards to local flying and en route operations. Obstacles inside and outside the aerodrome boundary may result in limitations on the distance available for take-off and landing and on the range of meteorological conditions in which operations can be undertaken. For these reasons certain areas of local airspace must be regarded as integral parts of the aerodrome environment. The degree of freedom from obstacles in these areas is as important in the granting and retention of an aerodrome licence as the more obvious physical requirements of the runways and their associated runway strips.

22.2Obstacle Identification Surface (OIS). Aerodrome obstacles are those obstacles that protrude through the OIS out to a distance of 15 km from the aerodrome. The obstacles are determined by survey and are detailed in the aerodrome entry in the AIP. The OIS is a complex plane starting with the cleared strip either side of the runway. From the cleared strip, the inner transition plane extends from surface to 45 m, and extends out to 3000 m from the edges of the strip. Beyond this, the outer transition plane lifts the OIS to 150 m and extends to the full 15 km.

Figure 22.1 Obstacle identification surface (OIS)

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Figure 22.2 Marking of objects

22.6 Vehicles and Mobile Objects. When mobile objects are marked by colour, a single conspicuous colour, preferably red or yellowish green for emergency vehicles and yellow for service vehicles should be used. Aerodrome operators are responsible for ensuring that vehicles on the movement area of an aerodrome are lit and/or marked as required irrespective of ownership. These include maintenance vehicles, ATC vehicles, ‘Follow Me’ vehicles, aircraft towing vehicles, refuellers etc. Whenever a permitted vehicle is on the movement area the lights are to be switched on. Vehicle obstacle lights are low intensity flashing yellow. The lights specified are to be fitted at the highest point of the prime mover. Trailers are to be lit with low intensity steady red lights at the highest point. Objects with limited mobility (air bridges etc.) are to be lit with low intensity steady red lights.

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22.9Low Intensity Lights. Low intensity obstacle lights on fixed objects shall be fixed red lights and have intensity sufficient to ensure conspicuity considering the intensity of the adjacent lights and the general level of illumination against which they would normally be viewed. Low intensity obstacle lights on objects with limited mobility such as aerobridges shall be steady-red. The intensity of the lights shall be sufficient to ensure conspicuity considering the intensity of the adjacent lights and the general levels of illumination against which they would normally be viewed. Where the use of low intensity obstacle lights would be inadequate or an early special warning is required, then medium or high intensity obstacle lights should be used.

22.10Medium Intensity Lights. Medium intensity obstacle lights shall be flashing red lights, except that when used in conjunction with high intensity obstacle lights they shall be flashing white lights. The flash frequency shall be between 20 and 60 per minute. Medium intensity obstacle lights located on an object should flash simultaneously. Medium intensity obstacle lights should be used, either alone or in combination with low intensity obstacle lights, where the object is an extensive one or its height above the level of the surrounding ground is greater than 45 m.

22.11High Intensity Lights. High intensity obstacle lights shall be flashing white lights. High intensity obstacle lights located on an object should flash simultaneously at a rate between 40 and 60 per minute. High intensity obstacle lights located on a tower should flash sequentially; first the middle light, second the top light and last the bottom light. High intensity obstacle lights 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.

22.12Tall Objects. Where an object is

indicated by low or medium intensity obstacle lights, and the top of the object is more than 45 m above the level of the surrounding ground or the elevation of tops of nearby buildings (when the object to be marked is surrounded by buildings) 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 45 m.

22.13 Lighting of Aircraft. The lighting of aircraft is detailed at Chapter 6 Rules of the Air. This subject is covered in detail in the OP syllabus. It should be noted that aircraft parked on the manoeuvring area are obstacles and should be lit either by the aircraft navigation lights or by ancillary lighting (anticollision) that determines the extremities of the aeroplane.

Figure 22.5 Tall objects