Aircraft warning lights
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Aircraft warning lights are high-intensity lighting devices that are attached to tall structures and used as collision avoidance measures. Such devices make the structure much more visible to passing aircraft and are usually used at night, although in some countries they are used in the daytime also. These lights need to be of sufficient brightness in order to be visible for miles around the structure.
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[edit] Lamp types
The lights generally come in two forms:
- Red lamps that are either constantly illuminated or turn on and off slowly in a cycle of a few seconds
- White xenon discharge flashers
Both types were in use in the United Kingdom until recently, however new regulations stipulate the use of red lamps at night-time only. Xenon flashers are therefore gradually being phased out.
In the United States and Canada it is common to find structures with xenon flashers during the daytime, and red lamps at night.
Traditionally, red lamps use incandescent filament bulbs. In order to improve the otherwise quite short lifespan, they are made with a ruggedised design and are run below normal operating power (under-running). A recent development has been the use of arrays of high power red LEDs in place of incandescent bulbs, which has only been possible since the development of LEDs of sufficient brightness. LED based lamps have a significantly longer lifespan than incandescent bulbs, thus reducing maintenance costs and increasing reliability.
Xenon flashers, whilst more visually impressive, tend to require frequent replacement and so have become a less favoured option.
[edit] Use and positioning
These lights can generally be found attached to any tall structure such as broadcast masts and towers, water tanks located on high elevation, electricity pylons, chimneys, tall buildings, cranes and wind turbines. Shorter structures that are located close to airports may also require lighting.
Lights are usually arranged in clusters around the structure at specific heights above the ground. Frequently there will be a set at the top, and then one or more sets equally spaced down the structure. England's Belmont mast (the tallest construction in the European Union) has nine clusters of red lamps spaced equally up and down the mast. This can also be found on the Winter Hill mast in Greater Manchester, which is 308 metres tall.
