If you’ve ever flown at night or in low visibility conditions (fog, rain, etc.), you will no doubt have noticed the lights which follow the markings on an airport’s runway to in order to guide pilots when it’s hard to make out the painted markings and symbols. Furthermore, these light vary in intensity according to varying conditions, because of course, a clear summer night for example offers conditions very different than those on a day (or night) of dense fog or driving rain.
Following are the primary and secondary lights you’ll find, along with their function and positioning:
Primary Runway Lights
The easiest to identify, these extend along precisely the runways, forming luminous white lines whose objective is to identify the limits of the track at night. They’re also omnidirectional, meaning they can be seen from any point. It’s common to see them when the airport operates at night and also during low visibility takeoffs and landings– for example, on runways with precision approaches, it’s common for the last third (or 600 metres/1,969 feet) of the runway edge lights to be yellow.
This is the beginning of the zone that’s available for landing, and at night it’s indicated by fixed green lights. While the runway edge lights are omnidirectional, these lights are unidirectional, that is, they are only visible from the side where the approach maneuver is being carried out.
Also fixed and also green, these lights are located on both sides of the runway threshold. And like the previous ones, they are only seen from the approach side. The wing bar lights continue, to the left and right, the line of green lights drawn by the runway threshold lights, so that they’re perceived visually a single line. These lights are only installed at airports where it’s necessary for whatever reason for the runway threshold to be particularly visible.
These are two white lights located to the left and right of the wing-bar line of lights. They aren’t fixed but rather blink between 60 and 120 times per minute. Their function, like that of the wing bar lights, is to make the threshold more visible.
End of the Runway
The runway end lights indicate where the landing zone ends. They’re fixed, red in colour, and like the runway threshold lights, they can only be seen from the place where the approach maneuver is being carried out.
Runway Centre-Line Lights
These too are unidirectional and cross the track along its central axis longitudinally. Although white, in the last 900m (2,953 ft.) we will see how the white lights alternate with red and, in the last 300m (984 ft.) they’re red only. It is a luminous warning that the end of the runway is approaching.
On the first section of the runway, on either side of the centre-line lights, the touchdown-zone lights alert us that an aircraft is about to touch down. They’re white, unidirectional, and are arranged in a kind of strip (rows of three white lights in a row that form an elongated rectangle). They extend along the first half of the runway or the first 900m (2,953 ft.), always starting from the threshold.
When the threshold is not located at the end of the runway, this is signaled by a section of red, fixed, unidirectional runway-edge lights.
Other Runway Lights
This acronym standing for approach lighting system, and these lights are located before the approach used to assist crews in their approach maneuvers. There are numerous configurations, and although some are recognized by the ICAO (International Civil Aviation Organisation), many are not. In any case, they are rows of lights that indicate that we are approaching the runway and that are aligned with the axis lights.
Visual approach indicators are lighting systems located on both sides of the runway, providing information to the pilot about its correct placement. As with ALS lights, there are some ICAO recognized VGSI lighting systems, although they depend on the specific regulation that governs each country. They are as follows:
- They consists of four variable lights (white or red) arranged horizontally on one side of the runway – generally the left, but on both if required. It is the most common approach lighting system in the world. They play with the two colours to indicate how excessively high or low we are flying relative to the glideslope.
- It’s a reduced version of the PAPI (Precision Approach Path Indicator) system, which uses two lights instead of four.
- In this case, the lights are arranged in two groups of two, they can be on only one side or on both, and their operation is very similar to that of the PAPI lights.
Photo | alvarez