Types of Obstruction Lights

Obstruction Lights are broadly divided into three following parts– 
· Low Intensity Obstruction Lights: These lights should be used where the object is a less extensive one and its height above the surrounding ground is less than 45 m. 
· Medium Intensity Obstruction Lights: Medium Intensity obstacle lights should be used where the object is an extensive one or its height above the level of the surrounding ground is greater than 45m. 
· High Intensity Obstruction Lights: These lights should be used to indicate the presence of an object if its height above the level of the surrounding ground exceeds 150m.

According to ICAO regulations Obstruction lights are divided in following types – 

· Low Intensity – Type A: Red color steady lights are used for fixed obstacles. Their minimum intensity should be 10 candelas. 
· Low Intensity – Type B: Red color steady lights are used for fixed obstacles. Their minimum intensity should be 32 candelas. 
· Low Intensity – Type C: These Yellow/Blue color flashing lights are used for mobile obstacles. Their minimum intensity should be 40 candelas. 
· Low Intensity – Type D: These Yellow color flashing lights are used for “Follow me” Vehicles. Their minimum intensity should be 200 candelas. 
· Medium Intensity – Type A: White color flashing lights are used for obstacles having height more than 45 meters. Their minimum intensity should be 2000 candelas. 
· Medium Intensity – Type B: Red color flashing lights are used for obstacles having height more than 45 meters. Their minimum intensity should be 2000 candelas. 
· Medium Intensity – Type C: Red colors fixed lights are used for obstacles having height more than 45 meters. Their minimum intensity should be 2000 candelas. 
· High Intensity – Type A: White color flashing lights are used for obstacles having height more than 150 meters. Their minimum intensity should be 2000 candelas. 
· High Intensity – Type B: White color flashing lights are used for obstacles having height more than 150 meters. Their minimum intensity should be 2000 candelas.

RESEARCH AND DEVELOPMENT

Obstruction Light Selection for Vertical Structures

1. Lower Level
2. Upper Level
3. More Than one level (Distance between levels 52m maximum) 
4. More Than one level (Distance between levels 75m maximum)

Need of Obstruction Light

Air accidents cause immense loss to human life and property. History is witness to innumerable air disasters. Accidents can be avoided by small precautions. Amongst various measures, visual aids are of immense importance in creating a safer sky. Tall, man-made structures and other geographical obstructions pose threat to airplanes in poor visibility. Low flying aircraft's, in spite of the modern navigational facilities on board, need prominent obstruction markings in their flight paths. These markings should be loud and clear to attract the pilot's attention. Obstruction Light is the solution to these problems, which warns pilot of any obstacle coming in the airway path.

Number of Lights

Number of obstruction lights to be placed on tall structures can be calculated by the following formula – 
Number of Lights = N = Y/45 
Where Y is the height of the Obstruction. 
Light spacing = X = Y/N <= 45m 
There should be at least 45-meter gap between two obstruction lights installed on tall structures. 

Applications 

• Wind Mills

• Bridges

• Buildings

• Turbines are lit as aviation obstructions.

• Cooling Towers

• Chimneys 

• Cranes

• Radio towers

• Television towers

• Communication towers

• Microwave towers

• Transmission line towers

• Wind cones

• Lighthouses

• Masts