What is Obstacle Lighting?
Lights fitted to towers, masts, chimneys, buildings and wind turbines so that pilots can see these fixed hazards and keep clear of them.
Obstacle lights are fitted to fixed objects that could endanger aircraft, so the object is visible to a pilot in poor light. They do not guide an aircraft along a path. They say one thing: something solid is here.
Lights come in three intensity classes. Low-intensity lights on fixed objects are fixed red. Medium-intensity lights are flashing white, flashing red or fixed red. High-intensity lights are flashing white. The taller or more extensive the object, the more intense the light that is normally needed.
Lights are placed to show the top and general outline of the object, with intermediate tiers on tall structures, and in numbers that make the object visible from every direction an aircraft could approach.
| Class | Light | Typical height | Peak intensity (typical) | Typical objects |
|---|---|---|---|---|
| Low | Fixed red | Under about 45 m | Type A about 10 cd; Type B about 32 cd | Buildings, low masts, cranes, small structures |
| Medium | Flashing whiteFlashing redFixed red | About 45 m to 150 m | Red about 2,000 cd; white up to about 20,000 cd by day | Masts, chimneys, wind turbines, tall buildings |
| High | Flashing white | Above about 150 m | Up to about 200,000 cd by day, reduced at twilight and night | Very tall towers, stacks and spans |
Find the object
Check the object against the airport's obstacle limitation surfaces and the surrounding airspace.
Study it
An aeronautical study decides whether the object must be marked, lit, or both.
Pick the class
Height and extent point to low-, medium- or high-intensity lights, or a dual system.
Lay it out
Place lights at the top, on intermediate tiers and around the outline so every approach direction is covered.
Do not treat obstacle lights as part of the runway or taxiway lighting. They are a hazard-warning system, and sit alongside other ways of making a hazard visible:
- Obstacle Marking→ paint, flags and markers that make the object visible by day
- Obstacle Lights→ make the object visible at night, and by day for the white flashing types
- Airfield Ground Lights→ guide aircraft on or toward the runway and taxiway
Obstacle lights are usually fed from a local supply with their own controller and monitoring, not from the airfield series circuits. The design for each site confirms this.
ICAO Obstacle Lighting
ICAO Annex 14 Volume I, Chapter 6, covers the marking and lighting of objects that could endanger aircraft. It groups obstacle lights into low-, medium- and high-intensity types. Low-intensity lights on fixed objects are fixed red; the one exception is Type E, a flashing red light used on the tower of large wind turbines. Medium-intensity lights are flashing white, flashing red or fixed red. High-intensity lights are flashing white. Lights are placed to show the top and general outline of the object, and enough of them are used for it to be seen from every direction in azimuth. Take the need for lighting, the type and the layout from the regulator's determination and the current edition of the standard.
FAA Obstruction Lighting
The FAA uses the term obstruction lighting and sets out marking and lighting in AC 70/7460-1, Obstruction Marking and Lighting. Its fixture types include L-810 (steady-burning red, low intensity), L-864 (flashing red), L-865 (flashing white, medium intensity) and L-856 (flashing white, high intensity). Confirm the current edition and which types apply to your structure and the FAA determination for it.
Frequently Asked Questions
Q1What is obstacle lighting?
Obstacle lighting is the set of aeronautical lights fitted to tall or otherwise hazardous fixed objects, such as towers, masts, chimneys, buildings and wind turbines, so that pilots can see and avoid them. Most are red at night; the brighter types are flashing white and also work by day.
Q2What are the three classes of obstacle light?
Low-intensity lights, which are fixed red; medium-intensity lights, which are flashing white, flashing red or fixed red; and high-intensity lights, which are flashing white. The taller or more extensive the object, the brighter and more conspicuous the lighting needs to be.
Q3Is it called obstacle lighting or obstruction lighting?
Both names refer to the same thing. ICAO Annex 14 uses the term obstacle lighting. The FAA, and many other sources, use obstruction lighting. This encyclopedia treats them as one subject.
Q4Who decides whether an object needs lights, and which class?
The aviation regulator decides, normally after an aeronautical study of the object and its position relative to the airport's obstacle limitation surfaces and the surrounding airspace. Height bands are a guide only. The regulator's decision, or the applicable national rules, governs.
Q5Are obstacle lights part of the airfield ground lighting system?
They are related but separate. Runway, taxiway and approach lights guide an aircraft on or toward the surface. Obstacle lights only warn of a fixed hazard. They are usually on their own supply, controller and monitoring rather than on the airfield series circuits, but the design for each site sets this.
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