Obstruction Lights

Obstruction Warning Lights in the Aviation Industry are of three types - the airport beacon, the identification or code beacon, and the hazard or obstruction beacon.

Airport Beacon : The airport beacon is normally located within 5,000 feet of the airfield.

Identification or Code Beacon : The identification beacon or code beacon identifies an airfield where the airport beacon is more than 5,000 feet away from the airfield or where two or more airfields are close enough to use the same airport beacon.

Hazard or Obstruction beacon (Obstruction Lights) : The Obstruction Light, indicates the visual identification of natural obstacles or structures which are 45 meters above airfield elevation for hazards like towers, buildings, tall bridges, communication towers etc.

Here we are going to discuss only Hazard or Obstruction beacon (or Obstruction Light).

The obstruction light is a system of red lights used to show the presence of manmade or natural objects that are dangerous to airway path. These obstruction lights are now days made from LED, Xenon Lamps, Neon Lamps, Incandescent lamps etc. Obstruction lights shall be located as close as practicable to the top of the object.

Obstruction lights are installed on all obstructions that present a threat to air traffic, cautioning pilots of the presence of an obstruction during hours of darkness and during periods of limited daytime visibility.

The obstruction shall be indicated by Low, Medium or High-intensity obstruction lights, or a combination of such lights according to the height of the structure (obstacle). The top lights shall be so arranged as to at least indicate the points or edges of the obstruction highest in relation to the obstacle limitation surface. An obstruction’s height, shape, size and the area in which it is located determine the position of obstruction lights on the obstruction and the number of lights required to light the obstruction.

Obstruction lights can be found both on and off an airport to identify obstacles.

Distribution of Obstruction Lights at Airway Path Obstacles

The obstruction light/s should be located so that it should reveal the top of the airway path obstacle. The obstacles which are not high above 45 meters, an obstruction light should be mounted on the top. However obstacles those are higher than 45 meters, multi-layer obstruction lights should be distributed at the obstacle but the separation should be less than 45 meters and as equal as possible.

Top Lights

At the top of the obstacle at least one obstruction light shall be installed. The light shall burn from sunset to sunrise and it should be positioned so as to insure unobstructed visibility of lights from aircraft at any normal angle of approach. The top obstruction light should be adjusted so that the lights will be turned on at about light intensity of 35 foot candles and turned off at about light intensity of 58 foot candles.

Intermediate Lights

The intermediate obstruction lights should be installed at approximately one-half of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this light from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

The intermediate obstruction lights should be installed at approximately two-fifths of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this light from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

The intermediate obstruction lights should be installed at approximately two-thirds and one-third of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this light from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

The intermediate obstruction lights should be installed at approximately four-sevenths and two-sevenths of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this light from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

The intermediate obstruction lights should be installed at approximately three-fourths, one-half and one-fourth of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this lights from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

The intermediate obstruction lights should be installed at approximately two-thirds, four-ninths and two-ninths of the total height of the obstacle in such position that the obstacle structure does not impair the visibility of this light from aircraft any normal angle of approach.  If the obstruction light cannot be installed in a manner to insure unobstructed visibility of it from aircraft at any normal angle of approach, two obstruction warning systems should be installed on the outer side of the obstacle at the prescribed height.

Extensive Obstacle

Where obstructions cover an extensive horizontal plane, the top lights will be put on the point or edge of the obstruction highest in relation to the obstruction-marking surface. The lights should not be spaced more than 150 feet apart. This spacing indicates the general extent of the obstruction. Double lights are used at the horizontal limits of the obstruction, and single lights are used for intermediate lights. If two or more edges are of the same height, the edge nearest the airfield is lit.