Airport Flashing Lights: What Do They Signal?

Airports are a sea of flashing lights, from the runway to the taxiways, and even the buildings nearby. These lights are not just for show, they are a crucial part of airport infrastructure, helping pilots navigate to and around the airport, especially at night or in low-visibility conditions. The lights are standardized across airports, with different colours and patterns serving different functions.

Runway lights

Runway edge lights are used to outline the edges of runways during periods of darkness or reduced visibility. These lights are white and are classified by their intensity or brightness: High-Intensity Runway Lights (HIRL), Medium-Intensity Runway Lights (MIRL), and Low-Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, while the LIRLs usually have one intensity setting. On instrument runways, the white lights change to yellow for the last 2,000 feet or half the runway length, whichever is less, to indicate a caution zone for landing or takeoff. A horizontal line of red lights marks the end of the runway.

Runway centerline lights are spaced at 50-foot intervals on large precision runways to improve visibility and help pilots keep their aircraft aligned during takeoff and landing. The lights remain white until the last 3,000 feet of the runway, where they alternate red and white for 2,000 feet, warning pilots that the end of the runway is approaching. The lights turn red for the final 1,000 feet.

Runway touchdown zone lights are installed on some precision approach runways to indicate the touchdown zone when landing in reduced visibility conditions. They consist of two rows of transverse light bars symmetrically placed across the runway centerline. These lights are steady-burning whites that start 100 feet beyond the landing threshold and extend to 3,000 feet beyond it.

Runway guard lights are installed at taxiway/runway intersections to enhance their visibility during low-visibility conditions. They consist of a pair of elevated flashing yellow lights installed on either side of the taxiway or a row of in-pavement yellow lights installed across the entire taxiway at the runway holding position marking.

Taxiway lights

Taxiway lighting aids pilots in identifying the centerline and edges of the taxiway, both during the day and at night. This lighting is particularly crucial during inclement weather or low-visibility conditions, helping to prevent ground collisions. For instance, keeping the aircraft's nose wheel on the taxiway centerline helps maintain clearance between parked aircraft and prevents collisions with airport structures.

The lights used in taxiways can be either LEDs or incandescent bulbs. Incandescent lights are typically found in older or smaller airfields due to their lower cost, but they have higher operational costs and shorter lifespans compared to LEDs. In colder regions, incandescent bulbs are preferred as they generate heat, helping to melt snow and increase visibility.

Additionally, taxiway centreline lead-on and lead-off lights provide visual guidance to pilots and vehicle drivers entering or exiting the runway. These lights are colour-coded, with green and yellow lights indicating the proximity to the runway environment or instrument landing system critical area. Runway entrance lights (REL) are another important feature, mounted in the pavement and focused along the taxiway centreline. These lights alert pilots to high-speed traffic on the runway or an aircraft on final approach.

Airport beacons

The colour of the beacon lights indicates the type of airport, such as civilian or military. For example, flashing white and green lights indicate a civilian land airport, while military airports feature dual-peaked white flashes alternating with green flashes. Beacons may also be omnidirectional capacitor-discharge devices, providing a constant speed of rotation to create the flashing effect.

In busy airspace, airport beacons are often turned on during the day when ground visibility is reduced or when the ceiling is low. However, this is not a strict rule, and the decision to activate beacons in these conditions is generally left to the discretion of Air Traffic Control (ATC) staff, who can control the beacons. Beacons are particularly useful in urban or densely populated areas where light pollution and obstructions can make it challenging to spot the airport.

To aid pilots further, some airports have implemented radio control of lighting systems, allowing pilots to control the lighting via their aircraft microphone. This feature is especially beneficial at locations without specified hours for lighting or where there is no control tower or Air Traffic Control staff present.

Runway guard lights

Runway holding point lighting is used as a means to reduce the risk of a runway incursion. They are positioned at each side of a taxiway at the marked and signed holding point where the taxiway is about to join a runway. Both aircraft and vehicles are required to wait at this point until given clearance by ATC to proceed.

Approach lights

The primary purpose of approach lights is to provide visual guidance to pilots, enabling them to identify the runway environment and align their aircraft with the runway during the approach for landing. This transition from instrument to visual flight is critical for safe operations, especially when visibility is reduced.

There are different configurations of approach lighting systems, recognised by the International Civil Aviation Organization (ICAO). These configurations vary in terms of the number of lights, their spacing, and the use of additional features like crossbars or side rows. The length of the approach light system can range from 420 metres in simpler configurations to 900 metres or more in more complex systems.

The intensity of approach lights can be adjusted to meet pilots' requests and to accommodate day and night operations. Additionally, some airports may have sequenced flashing lights as part of their approach lighting system. These lights typically flash in sequence, creating a sense of movement towards the runway.

Overall, approach lights play a vital role in aviation safety, providing critical visual cues to pilots during landing, ensuring they can accurately identify the runway and align their aircraft accordingly.

Frequently asked questions