Obstruction light

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Aviation obstruction lights
Classification and naming
The classification of aviation obstruction lights is as follows:
a) L-810, low-intensity red obstruction light
b) L-856, high-intensity white flashing obstacle light, 40 flashes/min
c) L-857, high-intensity white flashing obstacle light, 60 flashes/min
d) L-864, medium intensity red flashing obstruction light, 20 flashes/min-40 flashes/min
e) L-865, medium intensity white flashing obstacle light, 40 flashes/min
f) L-866, medium intensity white flashing obstruction light, 60 flashes/min
g) L-885, medium intensity red flashing obstruction light, 60 flashes/min
Extracted from: Civil Aviation Industry Standard of the People’s Republic of China MH/T6012-2015 [1] Aviation obstruction lights

Above picture: High Intensity Obstruction Light Type A, from Star Standard.

Aviation obstruction lights are generally divided into low intensity, medium intensity and high intensity. The vertical and horizontal distances of aviation obstruction lights are greater than 45 meters for buildings and their facilities, and the three types of obstruction marker lights can be used in conjunction with each other. Aviation obstacle indicator classification
Below 45 meters above the ground, low-intensity aviation obstruction lights should be set up in relatively open surroundings, which are always bright red.


Buildings and facilities 45 meters above the ground and 105 meters below the ground: use medium-intensity B-type aviation obstruction lights as red flashing lights, the flash frequency should be between 20-60 times per minute, and the effective light intensity is 2000cd±25%.


Use medium-intensity type A aviation obstruction light above 105 meters above the ground and below 150 meters; white flashing, effective light intensity (2000-20000cd) ± 25%.


For buildings and their facilities above 150 meters from the ground, use high-intensity obstacle signs and must be white flashing lights. The flash frequency should be between 20-70 times per minute. The effective light intensity depends on the brightness of the background. It works 24 hours a day.


Obstacles should mark the highest point and the extreme edge (ie, apparent height and width) of the obstacle. The distance between the middle layer must be no more than 45 meters, and the height of the city should be more than 100 meters. Special consideration should be given to adding aviation obstruction lights to the middle floors of buildings.


The vertical and horizontal distances of aviation obstruction lights should not be greater than 45 meters (that is, if the top of the object is more than 45 meters above the ground, the beacon must be obstructed in the middle)
For chimneys or other buildings of similar nature, the top obstacle marker light should be located between 1.5-3 meters from the top, taking into account the pollution of the chimney to the lamps.


The obstacle indicator light can be located 4-6 meters below the chimney mouth.
Ultra-high objects higher than 150 meters should be used in conjunction with medium and high-intensity aviation obstruction lights.
For high-voltage power transmission cables and towers less than 150 meters high, a white light-emitting medium-intensity aviation obstruction light can be installed on the top.


Regardless of the aviation obstruction lights, the number and arrangement of the aviation obstruction lights at different heights should be able to see the object or the “group outline” of the object from all aspects, and consider the simultaneous and sequential flashing of the obstruction lights to achieve Obvious warning effect.

Obstruction light

Above picture: Medium Intensity Obstruction Light, from Star Standard.

  1. The low-intensity obstruction light is constant light, red, and the peak light is stronger than 32.5cd. Generally, it is not used alone, but must be used in conjunction with medium-intensity and high-intensity obstruction lights. For example, the buildings and facilities above 45 meters are equipped with multi-layer medium-intensity or high-intensity obstruction lights, and low-intensity obstruction lights can be set between medium-intensity or high-intensity obstruction lights. (The low-intensity obstruction light is red, the effective light intensity is 100cd±25%)
  2. Medium intensity obstruction lights are divided into three types according to luminous requirements:
    a. The medium-intensity A-type obstruction light is a white flash with an effective light intensity of 20000cd-2000cd. It is used for buildings and facilities above 105 meters and obstacles with strong background light or used with high-intensity B-type light dimming.
    b. The medium intensity B-type obstruction light is a red flash, and the effective light intensity is 2000cd±25%.
    C. Medium intensity C-type aviation obstruction light is red constant light, effective light intensity is 2000cd±25%.
  3. The high-intensity obstacle lights are divided into two types according to the luminous requirements:
    a. The high-intensity type A obstruction light is a white flash, and it flashes with variable intensity at day, dusk or dawn and night. The effective light intensity is 200000cd±25% in daytime; 20000cd±25% at dusk or dawn; 2000cd±25% at night ; Mainly used for buildings and their facilities over 150 meters, or used in conjunction with medium intensity obstruction lights.
    b. The high-intensity B-type obstruction light is a white flash, and it flashes simultaneously at three levels of variable light intensity at day, dusk or dawn and night. The effective light intensity is 100000 cd±25% in daytime; 20000 cd±25% at dusk or dawn; 2000cd±25%, mainly used for marking wires, cable towers and high-voltage transmission line towers.
Obstruction light

Above picutre: Low Intensity Obstruction Light, from Star Standard.