When it comes to runway lighting, like with most aspects of airport design, safety comes first. Every airport that conducts aircraft operations must have a lighting system in place. Pilots can land and take off safely at night or in bad visibility situations thanks to the airport lighting system.

The runway lights are an important feature of the airport lighting system. They must be easily visible, work continually in all operational situations, and, of course, comply with ICAO requirements (compliant with international aviation regulations).

Lighting Types      

Approach Lights

The first lights that a pilot will reach during a landing are the approach lights. They have a white tint, are unidirectional, and can blink or stay constant. Before the runway, there are approach lights. Their primary purpose is to show which way the runway is facing.

The most advanced approach lighting system has a more complex structure and contains only white, yellow, and red lights. Such a system can be seen at major airports such as Dubai International Airport, Atlanta Airport, and Heathrow Airport.

Runway End Identification Light

This light, also known as the Runway Threshold Identification Light (or RTIL), is an unidirectional white flashing light that marks the start of a runway. Unlike approach lights, RTIL lights are only installed on one side of the runway.

Threshold Lights

Threshold lights are unidirectional green airfield lights put at the beginning of the part of a runway where planes can land. Threshold has yet to become a touchdown point. However, this is the start of the runway’s „safe-to-land“ section.

Runway Edge Light

The most essential lights on the airfield are the runway edge lights. They are situated on the runway’s left and right sides (edges) and illuminate the portion of the runway that is safe for landings.

These light systems are categorized based on the amount of energy they can produce:

• High-intensity runway lighting (HIRL)

• Medium-intensity runway lighting (MIRL)

• Low-intensity runway lighting (LIRL)

Although the majority of runway edge lights are clear or white, some outliers exist to provide additional information to pilots in specific situations. They last 600 meters, or one-half of the usable runway length (whichever is less) of an instrument runway lighting system and are bi-directional. They seem white to a pilot approaching from the short end of the runway, but they are yellow to a pilot approaching from the opposite end, who would be landing or taking off in that direction, indicating that the runway is approaching its end.

Runway End Light

The end of a runway is indicated with a runway end light. It signifies that there is no area for airplanes to continue moving behind these lights. Runway end lights are aviation lights that are unidirectional and red.

Taxiway Lights

Taxiway lights are airfield lights that are blue ioned on taxiways and aprons. A taxiway is a section of an airfield where planes move after landing on a runway. In comparison to runway edge or threshold lights, taxiway lights are not very bright. They’re also barely visible from the air. It isn’t required. Because the pilot only uses them when traveling around the airfield.

PAPI Lights

Precision Approach Path Indicator is a bicolor light that assists a pilot in maintaining the proper course when approaching an airport runway. PAPI lights are positioned on the runway’s left and right sides, a short distance from the threshold lights.

Typically, a PAPI light comprises four lighting fixtures (4x Light House Assemblies). Each lighting unit has the option of producing red or white light. All four lights will turn red if the aircraft is too close to the earth. If the plane is flying too high, all four lights will turn white. So, when two lights are white and two lights are red, you’re on the right track.

Runway Centerline Lights

White centerline lights are set every 50 feet on runways utilized for limited visibility operations to help pilots maintaining directional control during takeoff and landing. The lights alternate white and red for the last 3000 feet of runway. The runway’s final 1,000 feet have solid red centerline lights.

Rapid Exit

RETILs (Rapid Exit Taxiway Indicator Lights) may be used to indicate the distance to the nearest rapid exit taxiway.

Caution Zone

On ILS-equipped runways without centerline lighting, lighting may be provided. It is supplied by substituting yellow edge lights for the last 600 meters or one-third of the lit runway length to provide a visual notification of the approaching runway end.

Clearance Bar Lights

In low visibility conditions, clearance bar lights are put at holding positions on taxiways to boost the visibility of the holding position. During periods of darkness, they can also be used to identify the position of an intersecting taxiway. Three in-pavement steady-burning yellow lights make up the clearance bars.

Obstruction Aviation Lights

Obstruction aviation lights are omnidirectional red lights that illuminate airport structures, obstructions, closed areas, and sections on the airfield that are temporarily unavailable.

VASI and PAPI Lights

The VASI (Visual Approach Slope Indicator) is a series of lights organized to offer visual descent guidance information to VFR and IFR pilots during the approach to a runway.

During the day, these lights may be seen from 3-5 miles away, while at night, they can be seen from up to 20 miles away. Within plus or minus 10 degrees of the extended runway centerline and up to 4 NM from the runway threshold, the VASI’s visual glide path offers safe obstruction clearance.

You’re on the glide route if you see two red lights over two white lights. Even though conventional glide path angles are 3 degrees, VASI lights at some airports may be as high as 4.5 degrees to provide enough obstacle clearance.

Another prominently visible glide path indication light is the Precision Approach Path Indicator (PAPI). PAPIs employ comparable lights to VASIs, but they’re arranged in a single row of two or four light units. During the day, these lights may be seen from a distance of around 5 miles, while at night, they can be seen from a distance of up to 20 miles.

Lighting Intensity

The intensity of runway lighting must be adjustable to accommodate the complete range of horizontal visibility and ambient light in which the runway is intended to be used. When such a system is available, it must also be compatible with the intensity specified for the nearest portion of the approach lighting system. Flight crews are likely to ask ATC to alter runway lighting intensity so that it is bright enough to be useful but not so bright that it obstructs overall visual clarity.

The lights will be managed by the control tower at airports with control towers, taking into consideration visibility and pilot choice, but certain airports do not have control towers. Pilot Controlled Lighting, or PCL, will be installed at these airports, allowing pilots to alter lighting by pressing a microphone button a particular number of times.

To summarize, a runway includes many lights, some of which are primary and others secondary. The primary objective of those lights is always to ensure a safe landing and takeoff.

Sources

• https://en.wikipedia.org/wiki/Runway_edge_lights
• https://www.stantec.com/en/ideas/airport-runway-lights-what-are-they-all-for
• https://solutions4ga.com/runway-lights-at-airport-colors-and-meaning-explained/
• https://skybrary.aero/articles/runway-lighting
• https://aerosavvy.com/airport-lights/
• https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap2_section_1.html
• https://www.boldmethod.com/learn-to-fly/regulations/what-to-know-about-runway-lighting-spacing-and-color-configuration-explained/
• https://www.shutterstock.com (Cover image)