Taxiway Centreline Light for Airfield Ground Lighting

What It Is

Taxiway centreline lights provide longitudinal visual guidance along taxiway routes, helping pilots maintain alignment through straight sections, curves, intersections, rapid-exit taxiways and selected runway-entry areas.

Unlike taxiway edge lights, which identify the lateral limits of the pavement, centreline lights provide a visual reference along the intended aircraft movement path.

Selected According To

• Taxiway geometry
• Straight or curved section
• Taxiway intersection arrangement
• Rapid-exit configuration
• Low-visibility operating requirements
• Runway proximity
• Light colour sequence
• Optical beam width
• Directionality
• Fixture spacing
• Inset housing requirements
• Series-circuit characteristics
• CCR / intensity-control requirements
• Project technical specification

The System Helps Pilots

• Maintain taxiway alignment
• Follow curves
• Identify the intended taxi route
• Navigate complex intersections
• Transition toward runway-entry areas
• Follow rapid-exit taxiways
• Operate in reduced-visibility conditions

Performance Depends On

• Fixture location
• Fixture spacing
• Optical direction
• Beam width
• Light colour
• Intensity
• Taxiway geometry
• Fixture alignment
• Electrical circuit performance
• Control-system configuration

Why Inset

Taxiway centreline lighting is commonly implemented using in-pavement / inset fixtures, allowing the lighting system to operate along the aircraft movement path without creating an unacceptable surface obstruction.

The light fixture, housing and pavement interface should be treated as a coordinated installation.

Typical Installation

• Inset centreline fixture
• In-pavement housing
• Optical lens
• LED / light-source module
• Optical assembly
• Mounting hardware
• Gaskets and sealing arrangement
• Drainage provisions
• Secondary cable
• Isolating transformer
• Primary connector

Fixture Selection

Straight taxiway sections generally require a centreline fixture with an optical distribution suited to the intended aircraft viewing geometry. FAA guidance identifies:

• L-852A for applicable straight sections where RVR is at least 1,200 ft
• L-852C for applicable straight sections on low-visibility taxi routes below 1,200 ft RVR

Project Design Governs

The required beam configuration, intensity and colour arrangement should follow the applicable project design.

Why Curves Need Attention

Curves require special attention because the aircraft changes heading continuously. The system must provide enough visual information for the pilot to understand the path and direction of the turn.

FAA design guidance identifies wide-beam centreline fixtures for curved applications, including L-852B for applicable higher-RVR conditions and L-852D for low-visibility applications. The current FAA table also lists L-852J (RVR at or above 1,200 ft) and L-852K (below 1,200 ft) as wide-beam curve fixtures; confirm each fixture's beam handing and orientation against the curve direction on the approved drawing and the fixture photometric report, and check the beam angles in Table 1 of the current AC against the curve direction on the approved drawing.

Design Considerations

• Radius of curvature
• Fixture spacing
• Beam width
• Fixture orientation
• Number of visible lights
• Centreline geometry
• Aircraft cockpit viewing position
• Bidirectional vs unidirectional configuration

Colour Principle

For conventional taxiway centreline guidance, green is the principal colour. At specific runway-proximity locations, the configuration may incorporate yellow and green to provide additional visual information.

ICAO provisions specify green taxiway centreline lights for ordinary applications, with special green / yellow arrangements for exit taxiways and where proximity to a runway needs to be indicated.

The Colour Sequence Is Established From

• Taxiway function
• Runway proximity
• Exit configuration
• Direction of travel
• Critical / sensitive-area geometry
• Applicable standard
• Approved lighting layout

Exit Taxiway Layout May Need To Consider

• Runway centreline crossing
• Exit angle
• Runway proximity
• Critical / sensitive areas
• Taxiway curve radius
• Direction of aircraft travel
• Colour transition
• Intersection lighting
• Stop-bar location

ICAO’s taxiway-centreline provisions include specific green / yellow arrangements on exit taxiways and runway-proximity sections.

Acute-Angle Exits

The optical direction of the fixture is particularly important. FAA guidance states that unidirectional L-852A / L-852C fixtures are normally used on acute-angled exits, while bidirectional fixtures may be used where additional guidance for emergency vehicles approaching the runway is required.

Important During Selection

• Exit angle
• Fixture direction
• Beam width
• RVR
• Bidirectional requirement
• Emergency-vehicle movement
• Runway proximity

The Design May Incorporate

• Bidirectional centreline lights
• Unidirectional centreline lights
• Omnidirectional intersection lights
• Stop bars
• Clearance bars
• Runway guard lights
• Edge lights
• Lead-on / lead-off lighting

Fixture Guidance

FAA guidance separately identifies L-852E and L-852F omnidirectional yellow fixtures for taxiway intersections, with selection linked to RVR conditions.

The exact arrangement should follow the approved intersection lighting plan.

Control of Light Distribution

Centreline lights installed near a runway require careful control of light distribution. The purpose is to provide useful taxi guidance without creating ambiguity with runway visual aids.

ICAO notes the need to limit green light distribution near runways so that it does not create confusion with runway threshold lighting.

Key Selection Criteria at Runway Interfaces

• Beam control
• Fixture direction
• Colour sequence

Why It Matters

Taxiway centreline lighting is particularly important on designated low-visibility taxi routes.

FAA AC 150/5340-30J states that all low-visibility lighting systems needed for operations below 1,200 ft RVR are to be operated in accordance with the applicable low-visibility procedures, and identifies dedicated taxiway centreline fixture types for these routes.

Do Not Treat Every Centreline Fixture as Equivalent

Distinguish standard taxiway centreline lighting from low-visibility taxiway centreline lighting.

Low-visibility fixtures identified by FAA: L-852C (straight), L-852D and L-852K (curved) and L-852F (intersections).

ICAO Annex 14 requires taxiway centre line lights on taxiways intended for use in runway visual range conditions below 350 m, and recommends them on taxiways used at night in better visibility, particularly at complex intersections and exit taxiways, except where traffic density is light and edge lights and centreline marking give adequate guidance (see Chapter 5 of the applicable edition).

Potential Advantages

• Long operating life
• Reduced lamp replacement
• Lower routine maintenance
• Stable optical output
• Controlled beam distribution
• Consistent colour
• Improved energy efficiency
• Compatibility with modern AGL control and monitoring

Compliance

LED technology alone does not establish compliance.

The complete fixture must meet the applicable photometric, electrical, mechanical and environmental requirements.

Product Selection Should Consider

• CCR output current
• Series-circuit characteristics
• Transformer rating
• Fixture input requirements
• Number of fixtures
• Power consumption
• Connector type
• Secondary cable
• Intensity control
• Monitoring interface

Conventional AGL systems commonly connect centreline lights through a series circuit using isolating transformers.

Verify Before Replacing or Adding a Fixture

• CCR output current
• Fixture electrical characteristics
• Transformer rating
• Number of lights in circuit
• Primary and secondary cable
• Connector type
• Intensity steps
• Monitoring requirements
• Control-system interface

FAA Guidance

Series circuits for taxiway centreline and clearance-bar systems should be powered from an appropriately sized L-828 or L-829, Class 1, Style 2, five-step CCR, with brightness controlled by varying output current.

Final Circuit Design

The final airport circuit design should determine the required CCR and control configuration.

Construction May Include

• High-strength in-pavement body
• Inset housing
• Optical lens
• LED module
• Reflector / optical assembly
• Sealing gasket
• Stainless-steel hardware
• Secondary cable interface
• Drainage arrangement

Take exact construction from the selected manufacturer’s current technical documentation.

Evaluate For

• Rain and water ingress
• Dust and humidity
• Temperature variation
• UV exposure
• Corrosion
• Vibration
• Aircraft loading
• Pavement contamination
• Cleaning chemicals
• Mechanical impact

For inset installations: water ingress + drainage + sealing + pavement interface + mechanical loading.

Pavement & Housing Coordination

• Pavement construction
• Housing dimensions
• Fixture dimensions
• Cut-out dimensions
• Installation depth
• Drainage and sealing
• Mounting hardware
• Cable routing
• Maintenance access

The approved installation drawing should control all dimensional requirements.

Installation Alignment

Correct alignment is essential. Verify:

• Fixture position relative to centreline
• Optical direction
• Fixture spacing
• Curve and intersection geometry
• Colour sequence
• Fixture elevation / level
• Housing orientation
• Runway interface