At night time every major airport in the world will display an array of differently coloured lights for different functions. Obviously, pilots need to be able to see clearly in the dark when taking off or landing, but there are several categories of airport lighting: general lights, taxiway lights, runway lights, and approach lights.
The most prominent lighting in this category is the airport beacon. This is a big, powerful light that creates an easily spotted checkpoint for cross-country pilots flying at night. The beacon is green and white at civilian airports, but military airports are differentiated by two white lights for each green one. It may be set to a timer or switched on and off by an Air Traffic Controller.
Buildings, construction equipment, towers, and other tall structures will be lit by a steady red beacon to guide low-flying aircraft. Green, white, and red rotating lights are used at heliports.
There are several types.
Taxiway edge lights: blue in colour, they delineate the taxiway’s border. Often there are green lights marking the centerline too.
Clearance bar lights: steady yellow, sited within the taxiway, these enhance visibility at taxiway intersections and hold lines.
Stop bar lights: steady red in-pavement lights, only used at some airports, indicating Air Traffic
Control clearance in situations of poor visibility.
Runway guard lights: a pair of steady yellow lights set at each side of the taxiway, indicating the hold short line.
Again there are a number of types.
Runway end identifier lights: a pair of flashing white lights showing the runway approach.
Runway Edge light systems: steady white lights that change colour as the aircraft comes into land.
Runway centerline lighting system: steady white lights at the runway’s edge which change colour when the airplane approaches at 3,000 and 1,000 feet.
Touchdown zone lights: two rows of white lights by the centerline, indicating the midpoint of the runway.
Land and hold short lights: white lights that flash while these processes are in operation.
Approach lights are visual indicators of an aircraft’s position inside the glide slope: the instrument landing-system guide path These lights enable pilots to maintain stability during descent. There are two categories of approach lights, Visual Approach Slope Indicator (VASI) and Precision Approach Path Indicator (PAPI).
VASI: bars of lights sited at the runway’s sides, showing the pilot whether the aircraft is coming in too high or too low. VASI can be based on 2 to 16 lights arranged in 2 or 3 bars.
PAPI: arranged horizontally, these red and white lights glow according to the airplane’s position within the glide slope.
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