Airports And Path Lights: A Necessary Investment?

Airports are complex operations, and lighting plays a critical role in ensuring the safety of aircraft, pilots, and passengers. All operational airports must be equipped with lighting systems to aid pilots during takeoff and landing, especially at night or during low-visibility conditions. These lighting systems are standardized by the International Civil Aviation Organization (ICAO) and implemented by national aviation regulators. While the specifics of airport lighting can vary depending on the airport's size, location, and other factors, there are several key types of lights that are commonly used to ensure safe and efficient operations.

Runway Edge Lights

Runway edge lighting systems are classified by how bright the lights can be: High-Intensity Runway Lights (HIRL) are the brightest, followed by Medium-Intensity Runway Lights (MIRL), and then Low-Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, while the LIRLs usually have one intensity setting.

The lights marking the ends of the runway emit red light towards the runway to indicate the end of the runway to departing aircraft. Runway end lights are unidirectional red lights.

Runway Approach Lights

Approach Light Systems (ALS) are a standard feature of airport runways, consisting of a series of light bars, strobe lights, or a combination of both. These lights are positioned symmetrically on both sides of the runway's extended centreline, starting at the landing threshold and extending outward into the approach zone. The length of this lighting system can vary, typically ranging from 2400 to 3000 feet for precision instrument runways and 1400 to 1500 feet for non-precision instrument runways.

The design of ALS can be categorised into two main types: Simple ALS and Precision Approach Category Lighting Systems. Simple ALS is utilised for non-instrument runways and non-precision approach runways. In contrast, Precision Approach Category Lighting Systems are further divided into Category I and Category II/III lighting systems, which offer more advanced features.

The Simple ALS typically consists of a row of lights extending at least 420 metres from the threshold, with a crossbar of lights positioned 300 metres from the threshold. This system provides basic visual guidance to pilots.

On the other hand, the Precision Approach Category I Lighting System employs a more complex arrangement. It features a row of lights extending 900 metres from the runway threshold, with crossbars added at specific intervals. The first 300 metres use a single light source, while the next 300 metres use two light sources, and the final 300 metres utilise three light sources.

The Category II/III Lighting System shares a similar design to the Category I system but incorporates additional side rows of lights and differs in the spacing and arrangement of crossbars.

The brightness of these approach lights can be adjusted to suit day and night operations, and some systems incorporate sequenced flashing lights that create the illusion of a ball of light travelling towards the runway, aiding pilots in their final approach.

In addition to the standard ALS configurations, there are also non-standard variations installed at certain airports, such as the Short Approach Lighting System and the Helicopter Approach Lighting System.

Runway End Lights

In addition to Runway End Lights, Runway Threshold Lights, which are green in color, define the beginning of the declared landing distances at the touchdown end of a runway. These lights can only be seen from the approach and indicate the start of the safe zone for landing.

To further enhance runway identification, Runway End Identifier Lights (REILs) are often installed. These are bright, synchronized flashing lights positioned on both sides of the runway threshold. They can be seen from miles away, even during the day, and provide an additional layer of safety during reduced visibility.

Runway Centerline Lights

When viewed from the landing threshold, the runway centerline lights are white until the last 3,000 feet of the runway. This is when the white lights begin to alternate with red lights for the next 2,000 feet, warning pilots that the end of the runway is approaching. For the final 1,000 feet of the runway, all the centerline lights are red.

Centerline lights are often mounted a few inches left or right of the actual centerline. During takeoff, it is not uncommon for one of the nose wheels to run over the lights, which are designed to withstand the weight of wide-body jets landing on them.

Taxiway Lights

Taxiway lighting is crucial for pilots to clearly see the centreline and edges of the taxiway, especially during low-visibility conditions caused by inclement weather or darkness. By following the taxiway lights, pilots can maintain proper clearance from obstacles, parked aircraft, and airport structures. Additionally, these lights play a vital role in enhancing situational awareness, which is critical for preventing accidents on the ground, such as the 1977 Tenerife disaster.

Types of Taxiway Lights:

• Taxiway Centerline Lights: These lights follow the painted taxiway centreline and emit a steady green light. They are bidirectional and help pilots keep their aircraft centred during taxiing.
• Taxiway Edge Lights: These blue lights are placed at regular intervals along the edges of the taxiway, providing a clear outline of the taxiway boundaries. They are omnidirectional but have low intensity to avoid creating a chaotic appearance on the airport grounds.
• Clearance Bar Lights: These lights consist of three steady-burning yellow lights placed perpendicular to the taxiway, indicating holding positions. They are mandatory during very low-visibility operations and are used to warn aircraft and ground vehicles of upcoming taxiway intersections.
• Runway Guard Lights (RGLs): Similar to Clearance Bar Lights, RGLs are placed before runway holding points to warn taxiing aircraft that they are approaching an active runway. They can be either a row of in-pavement yellow lights or a pair of elevated flashing yellow lights on either side of the taxiway.
• Stop Bar Lights: These unidirectional red lights are placed before runway holding points, serving as a warning signal for aircraft and vehicles. They indicate that it is unsafe to enter the active runway and must be crossed only after confirmation from air traffic control.
• Taxiway Centreline Lead-Off Lights: These lights alternate between green and yellow, indicating the transition between a runway and a taxiway. They help pilots and vehicle drivers understand when they are within the boundaries of the runway or the Instrument Landing System (ILS) critical area.
• Taxiway Centreline Lead-On Lights: Similar to Lead-Off Lights, Lead-On Lights are installed on entry taxiways, guiding pilots as they enter a runway or an ILS critical area. These lights are bidirectional and work in conjunction with sensors to provide complementary visual guidance.

Other Taxiway Lighting Considerations:

Frequently asked questions