Lights play a vital role in aviation than we can ever imagine. The cover picture might look like a child’s coloring book but trust me everything there is meticulously and strategically positioned to serve a purpose that makes for safe flying. I will focus on aircraft lights and airport lights.
As you can see from the illustrative picture above. An aircraft is adorned with an array of brightly coloured lights all over its fuselage. There are basically 5 distinct lights that every aircraft should have to meet the minimum safety requirements of flying. Position lights are on the wingtips, green on the right and red on the left. Each wing tip also has a white light facing the rear. The lights are always on. When pilots see another aircraft’s white position lights, they know its flying away from them.When they see red and green lights, they know its heading towards them. The lights help determine aircraft position and direction. The red lights on the under belly and top of the fuselage are called beacon lights. Landing lights located on the nose wheel landing gear and front wing parts that attach to the fuselage.
Airport lights can be divided into different types: General airport lighting, taxiway lighting, runway lighting, and approach light systems.
General Airport Lighting
General airport lighting usually includes the airport beacon and any white or red beacon lights on top of towers, buildings, and construction equipment.
The airport beacon is a large, powerful rotating light that’s highly visible from miles away. Public use airport beacons rotate green and white. Military airports rotate green and white, but have two white lights for each green light, which differentiate them from civilian airports. And heliports rotate between green, white and yellow lights. Pilots flying cross-country can easily identify an airport at night from its beacon, making it one of the easiest checkpoints for pilots when navigating at night Sometimes air traffic controllers can turn the beacon on and off as necessary; other times it’s set on a timer.
Airport buildings, towers, and other tall equipment on the field will have a small, steady red beacon on top of them to aid in collision avoidance for low-flying aircraft.
Taxiways are used by aircraft to navigate from the boarding gates to their takeoff positions. These routes can be quite long therefore proper markings especially at night is very crucial.
- Taxiway Edge Lights: Taxiway edge lights are blue in color and line the taxiways. Airports often have green taxiway centerline lights, as well.
- Clearance Bar Lights – Set inside the taxiway, clearance bar lights are steady yellow and are meant to increase the visibility of a hold line or a taxiway intersection at night.
- Runway Guard Lights – A pair of two steady yellow lights that are positioned at each side of the taxiway at the hold short line, the runway guard lights are meant to draw attention to the hold short line – the area where a taxiway meets the runway.
- Runway End Identifier Lights (REILs): A pair of white flashing lights, one on each side of the approach end of the runway, that help identify the runway from taxiways at night.
- Runway Edge Light Systems (HIRL/MIRL/LIRL): The runway edge lights are steady white lights on the edges of the runways. On instrument runways, the white lights change to yellow during last 2,000 feet, or half the runway length, whichever is less, and then they turn red as the aircraft reaches the end of the runway. They can be high-intensity (HIRL), medium-intensity (MIRL) or low-intensity (LIRL).
- Runway Centerline Lighting System (RCLS) – On some precision runways, a runway centerline light system is installed, with white lights spaced at 50-ft intervals on the centerline of the runway. With 3,000 feet remaining, the white lights change to alternating white and red, and then all red during last 1,000 feet.
- Touchdown Zone Lights (TDZL) – Touchdown zone lights are steady white lights placed in two rows next to the centerline, starting at 100 feet and extending to the midpoint of the runway, or 3,000 feet beyond the threshold, whichever is less.
- Land and Hold Short Lights – When land and hold short operations (LAHSO) are in effect, flashing white lights may be seen across the runway at the hold short line.
- Other runway lighting may include Runway Status Lights (RWSL), which includes Runway Entrance Lights (RELs), the Takeoff Hold Light Array (THL), Runway Intersection Lights (RILs), and the Final Approach Runway Occupancy Signal (FAROS). These lights work in conjunction with surveillance systems(like ADS-B) and are fully automated. They assist in informing pilots and ground vehicle operators when it’s safe to enter or cross a runway.
Visual Glide-slope Indicators
Visual glideslope indicators are meant to give pilots a visual guide during their descent in order to maintain a stabilized approach. They come in two types, VASIs and PAPIs, each of which has multiple types of arrangements, but both of which give pilots a good idea whether they’re on glide path for a stable approach or not.
- VASIs/ Visual Approach Slope Indicators are bars of lights on the side of the runway that, when illuminated, give pilots a visual indication of whether their aircraft is too high or too low on the approach. VASIs can be made up of 2, 4, 6, 12 or 16 lights, usually located on two or three bars – near, middle and far. Two-bar VASIs provide an indication for a 3-degree glideslope, which is typical for what should be flown during an approach. In a common two-bar VASI system, a pilot should see two red lights on the far bars and two white lights on the near bars. If all lights on the near and far bars are red, he is too low. If all lights on the near and far bars are white, he is too high. The rule of thumb pilots use is “red over white, you’re alright.”
- PAPI stands for Precision Approach Path Indicator. PAPI lights are arranged horizontally, and typically include four lights that can be red or white, depending on where the aircraft is n the glideslope. A typical PAPI system is located on the left side of the runway. When all four lights are white, the aircraft is too high. As it descends onto the glide path, the lights on the right side will begin to turn red. When an aircraft is on the precise glide path, the two left lights should be white, and the two right lights should be red. When three or more lights are red, it indicates that the aircraft is too low.
The view from the flight deck on final. This is how the pilots flying your plane see the runway as they are preparing to land. Nice view though, dont you agree?
So next time you are flying or at an airport especially at night, familiarise yourself with the lighting system there. Some airport like Osaka Itami International in Japan and Beijing Capital International in China have colorful and picturesque lighting design that awe even most passionate aviation enthusiasts. Put that on your list of to see things if you travel a lot by air.
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