Approach Lighting
Approach Centreline Light for Airfield Ground Lighting
Longitudinal guidance toward the runway
Approach centreline lights form the principal longitudinal visual reference of many approach lighting systems, extending from the runway threshold along the extended centreline through project-specific steady-burning or configured arrangements.
Supplied by Precision AGL Solutions
Product Overview
Approach Centreline Light
What It Is
Approach centreline lights form the principal longitudinal visual reference of many approach lighting systems, extending outward from the runway threshold along the extended runway centreline.
The centreline gives the pilot a key reference during the transition from instrument navigation to the visual portion of the approach.
It Assists With
- Runway alignment
- Approach-path recognition
- Horizontal reference
- Visual transition toward the runway
- Runway orientation during night operations
- Reduced-visibility operations
Selected According To
- Approach category and runway classification
- Approach lighting system type and length
- Centreline light-bar and crossbar arrangement
- Steady-burning or flashing configuration
- Optical direction, colour, intensity
- Mounting arrangement and spacing
- Electrical circuit
- Control and sequencing requirements
- Project technical specification
The exact arrangement depends on the approach category, runway configuration, applicable lighting system and governing standard.
Applications
Where Approach Centreline Lighting Is Used
Simple approach systemsCentreline-based.
Non-precision approach runwaysInstrument runways.
Precision Category IExtended centreline.
Precision Category II / IIIAdvanced configuration.
Medium-intensity systemsMALS / MALSF / MALSR.
Other configured systemsSystem-specific.
Runway upgradesAirport projects.
Approach rehabilitationReplacement of equipment.
New runway constructionNew installations.
ICAO specifies a 900 m extended-centreline arrangement for a precision approach Category I system wherever practicable. FAA MALS/MALSF/MALSR systems use approach lighting along the extended runway centreline with system-specific steady-burning bars and sequenced flashers.
Function
A Visual Reference Leading to the Threshold
Primary Functions
- Establishing runway alignment
- Longitudinal approach guidance
- Identifying the runway approach axis
- Visual transition from instrument to visual flight
- Horizontal reference through the approach area
- Roll and alignment perception in configured systems
FAA MALSR
FAA describes MALSR as giving pilots runway alignment, height perception, roll guidance and horizontal references to support the visual portion of an instrument approach.
Configuration
Approach Centreline Configuration
Can Be Configured As
- Single point light sources
- Light barrettes and steady-burning light bars
- Integrated centreline assemblies
- Centreline lights with associated crossbars
- Centreline systems with sequenced flashers
- System-specific modular approach-light fixtures
Light Bar & Barrette
- Single light source
- Linear light bar or multi-lamp barrette
- Modular LED bar
- Integrated crossbar assembly
- Approach-light tower or support assembly
Select the product according to the complete approach lighting system, not only the individual light source. ICAO allows a simple-system centreline light to be a single source or a barrette at least 3 m long.
Simple Approach Lighting
Simple Approach Lighting System
ICAO
ICAO specifies fixed centreline lights, each a single light source or a barrette of at least 3 m. Where point sources form a barrette, 1.5 m spacing between adjacent lights has been found satisfactory. The row extends wherever possible for not less than 420 m from the threshold, with a crossbar of 18 m or 30 m at 300 m.
Phased Development
ICAO notes longer barrettes may be appropriate where future development into a precision approach system is anticipated — making centreline design particularly relevant during phased airport development.
Precision Approach
Precision Approach Centreline Lighting
Category I
ICAO specifies a row of centreline lights on the extended runway centreline, extending wherever possible to 900 m from the threshold, with crossbar elements per the applicable configuration.
Category II / III — Coordinate With
- Crossbars and side rows
- Sequenced flashing lights where provided
- Runway threshold and centreline lights
- PAPI / precision approach visual aids
- ILS / other approach navigation systems
FAA Systems
FAA Approach Lighting Systems
MALSMedium Intensity Approach Lighting System.
MALSFMALS with Sequenced Flashing Lights.
MALSRMALS with Runway Alignment Indicator Lights.
MALSR Provides
A combination of steady-burning light bars and sequenced flashers giving runway alignment, height perception, roll guidance and horizontal references.
MALSR Centreline Arrangement
Nine sets of five white steady-burning light sources: seven bars at 200 ft intervals and two offset bars associated with the 1,000-ft bar. The sequenced-flasher array has five white flashing lights at 200-ft intervals on the extended centreline.
Take the exact configuration from the current approved FAA design and applicable system drawing.
Operation
Steady-Burning vs Sequenced-Flashing Elements
Steady-Burning Centreline Lights
Provide continuous longitudinal and horizontal visual references.
Sequenced Flashers
Provide dynamic directional information and help identify the approach path (MALSF, MALSR). The two functions are not interchangeable.
Flasher Integration — Coordinate
- Flasher spacing and flash sequence
- Synchronization and flash rate
- Intensity and direction
- Control system
Treat Flashers Separately
MALSR uses five sequenced flashers on the extended centreline. Treat flasher equipment as a separate functional element even when supplied with the complete system.
Light Colour
White Centreline, Verified Per System
Colour
White is the principal colour for the centreline reference. ICAO selects colour so the approach system is readily distinguishable from other aeronautical ground lighting and extraneous lighting. FAA MALSR uses white steady bars and white flashers, with green threshold lighting.
Verify Against
- Approach system type
- Runway threshold arrangement
- Applicable authority
- Project drawing
- Manufacturer configuration
Optics
Optical Direction & Beam Distribution
Designed Around Viewing Geometry
- Fixed and directional, or broad enough for the approach sector
- Integrated within a light bar
- Steady-burning or sequenced-flashing output
For simple systems ICAO requires the necessary azimuth visibility and adequate intensity for the visibility and ambient-light conditions.
Photometric Design Considers
- Horizontal beam spread and vertical coverage
- Main beam axis and viewing range
- Aircraft approach angle
- Centreline alignment
- Ambient background lighting
The objective is a continuous, identifiable visual reference from the intended approach region without unnecessary optical spill.
Approach Geometry
Coordinate With the Complete Approach Geometry
Extended runway centrelineReference
Centreline light stationsPositions
CrossbarsHorizontal reference
Side-row elementsLateral reference
Runway thresholdBoundary
Runway centrelineContinuation
Crossbar Coordination
- Crossbar length and position
- Centreline station
- Side rows and runway threshold
- Applicable approach category
Crossbars help the pilot assess alignment, roll and position relative to the runway.
Layout To Confirm Before Procurement
- Threshold position and approach centreline
- System length and light stations
- Crossbar, side-row and flasher stations
- Support locations, cable routing, control location
A centreline product cannot be evaluated correctly without considering the complete arrangement.
LED Light Source
LED Technology in Approach Centreline Systems
Potential Advantages
- Long operating life
- Reduced lamp replacement and routine maintenance
- Consistent light output and stable colour
- Controlled photometric distribution
- Reduced energy consumption
- Improved monitoring possibilities
Compliance
Where lamp-based systems remain specified, match the lamp and optical assembly to the approved system. LED technology by itself does not establish compliance.
Electrical Characteristics
Architecture Is System-Specific
Design May Include
- Constant-current supply
- Dedicated approach-lighting circuits
- Series-circuit supply
- Individual isolation transformers
- Local control equipment
- Sequenced-flasher control
- Intensity switching, monitoring circuits, control cabinets
Do Not Assume
Approach lighting may use electrical architectures different from runway and taxiway series circuits. Match the product to the specific approach lighting system, not to a runway centreline light.
Series circuit: AGL Power / CCR → Primary Circuit → Isolating Transformer → Secondary Connection → Approach Centreline Light
Centralized: Control Panel / ALCMS → Approach Lighting Control → Steady-Burning / Flasher Circuit → Approach Centreline System
The actual system architecture is project-specific.
Intensity Control
Intensity Matched to System Design and Ambient Conditions
Verify
- Maximum intensity and intensity steps
- Low/high intensity
- CCR compatibility
- Flasher intensity
- System synchronization
FAA Documentation
Identifies system-specific intensity control for steady-burning approach systems and distinguishes sequenced-flasher operation from steady-burning elements.
Mechanical Installation
Supports, Obstacles and Environment
May Be Installed Using
- Elevated light supports and light towers
- Frangible structures and low-level supports
- Flush/in-pavement arrangements where approved
- Modular light bars
FAA guidance identifies low-impact-resistant support structures for approach-light installations. ICAO requires elevated approach lights and their supports to be frangible; beyond 300 m from the threshold, where a support is taller than 12 m, frangibility applies to the top 12 m only (Annex 14, Chapter 5 — confirm against your edition).
Approach-Area Review
- Approach surface, structures, terrain
- Drainage, access roads, maintenance access
- Frangibility and light-support structures
- ILS/MLS installations, obstacle limitations
Environmental Exposure
- Rain, dust, humidity
- Temperature variation, UV, corrosion
- Wind, vibration, electrical surges
- Wildlife, cleaning/maintenance activities
Alignment Is Critical
- Runway centreline reference and extended centreline
- Station location, light-bar and crossbar alignment
- Azimuth, elevation, tilt, beam axis
The centreline establishes the visual runway axis.
The applicable airport design determines final support and clearance arrangements.
Commissioning & Testing
System-Level Commissioning
Visual & Electrical
- Light, lens, colour, light-bar, supports, frangible components
- Alignment, station location, crossbar relationship, cables
- Continuity, insulation resistance, CCR operation
- Transformer verification where applicable, intensity steps
- Control-panel operation and monitoring
Photometric & Flasher
- White output, intensity, beam distribution, optical direction
- Centreline alignment, crossbar visibility, consistency
- Flash sequence, synchronization, rate, intensity
- Failed-flasher indication and control response
Inspection & Maintenance
Optical, Mechanical, Electrical and Alignment
Optical & Mechanical
- Lens cleanliness and damage, light output, colour
- Beam direction and contamination
- Light-bar condition, supports, mounting
- Frangible components, fasteners, corrosion, structure
Electrical & Alignment
- Cable, connector, transformer, CCR
- Control panel and monitoring
- Centreline position, azimuth, elevation
- Crossbar and flasher alignment
Common Failure Modes
Symptoms and Possible Causes
| Symptom | Possible Causes |
|---|---|
| Centreline light OFF | Circuit failure; light-source failure; transformer fault; cable fault; connector failure; control problem |
| Low light output | Optical contamination; LED/lamp degradation; incorrect intensity setting; electrical problem; damaged optical assembly |
| Incorrect alignment | Support movement; installation error; structural damage; incorrect adjustment; survey/set-out error |
| Uneven centreline appearance | Different output levels; failed light source; contamination; mixed fixture configurations; incorrect intensity settings |
| Flasher not operating | Flasher failure; sequencer/control failure; circuit interruption; synchronization fault; power/control-system issue |
| Inconsistent approach pattern | Missing light; incorrect station location; support displacement; crossbar problem; flasher sequence problem; control-system configuration |
Engineering Troubleshooting Sequence
Use a Systematic Diagnostic Sequence
Approach control systemCommand
CCR / power supplyVerify
Primary circuitCheck
Transformer / local powerCheck
Secondary connectionCheck
Centreline fixtureCheck
Light sourceInspect
Optical alignmentInspect
PhotometryVerify
Where flashers are installed: Sequencer → Flasher Controller → Flasher Circuit → Individual Flasher → Synchronization.
Product Selection Matrix
Key Selection Parameters
| Selection Parameter | Requirement |
|---|---|
| Application | Approach lighting |
| Approach type | Simple / Non-precision / Precision |
| Category | Project specific |
| System | MALS / MALSF / MALSR / ICAO system |
| Installation | Elevated / system-specific |
| Centreline | Extended runway centreline |
| Light source | LED / approved technology |
| Colour | White / system-specific |
| Operation | Steady / flashing where applicable |
| Beam / Intensity | Project specific |
| Spacing | System/layout dependent |
| Crossbar / Flasher | Required / not required |
| Support | Elevated / frangible / project-specific |
| Circuit | Project specific |
| Control / Monitoring | Local / centralized / ALCMS; project specific |
| Environment | Airport specific |
| Documentation | TDS / photometry / certificates |
Product Selection Checklist
Before Ordering, Confirm
- Airport / project
- Runway designation and threshold
- Approach category
- Approach lighting system
- Simple / precision arrangement
- System length and extended centreline
- Centreline light-bar configuration
- Crossbar and side-row configuration
- Steady-burning requirement
- Sequenced-flasher requirement
- Light colour
- Beam distribution
- Intensity and intensity steps
- Light spacing
- Support structure and frangibility
- Cable arrangement
- CCR / power supply
- Transformer requirement
- Control interface and monitoring
- Environmental requirements
- Applicable standard
- Manufacturer TDS
- Photometric documentation
- Type-test/compliance documentation
- Project approval requirements
Technical Documents
Technical Documents to Request
For technical approval and procurement, request the applicable manufacturer documentation.
- Product datasheet
- Technical specification
- Photometric report
- Beam distribution diagram
- Colour/chromaticity information
- Light-bar/barrette dimensions
- Centreline layout information
- Crossbar interface
- Flasher information where applicable
- Electrical specification
- Rated operating current
- Power consumption
- Transformer requirement
- CCR compatibility
- Connector details
- Mounting drawing
- Support-structure information
- Frangibility information
- Installation dimensions
- Cable-routing information
- Control/interface diagram
- Monitoring information
- Weight
- Material specification
- Environmental rating
- Installation manual
- Maintenance manual
- Compliance certificates
- Type-test reports
- Warranty information
Standards & References
Governing Standards
ICAO
Annex 14 Vol. I is the 9th Edition (July 2022). Amendment 18 took effect on 4 August 2025; its aerodrome-design and visual-aids provisions apply from 27 November 2025 (ground handling from 26 November 2026, obstacle limitation surfaces from 21 November 2030). Annex 14 distinguishes simple and precision approach lighting systems. Simple: fixed centreline lights, single sources or barrettes of at least 3 m. Category I: centreline row on the extended centreline, wherever possible 900 m from the threshold, with the applicable crossbar arrangement. Verify the edition and amendments for each project.
FAA
FAA Order JO 6850.2C (Visual Guidance Lighting Systems, 30 August 2022) gives the installation criteria for approach lighting systems including MALS, MALSF and MALSR.
AC 150/5340-30J carries installation details for MALSF and other airport visual aids.
AC 150/5345-46F is the active fixture specification; its L-850 series covers in-pavement runway fixtures, including L-850A/L-850B for runway centreline and touchdown zone and L-850E, the unidirectional threshold light introduced for use with medium-intensity approach lighting. These are in-pavement (semi-flush) fixture types. Elevated approach-light fixtures and the sequenced flashers (AC 150/5345-51B) are separate types. Confirm the classification from the approved system.
India — Also Verify
- DGCA requirements
- Airport-specific AGL specification
- Approved approach-lighting layout
- Approach category and instrument approach procedure
- PAPI/approach-aid coordination
- Project BOQ and Employer’s requirements
- Applicable Indian Standards
- Airport operator requirements
Always verify the applicable document edition and project-specific requirements before procurement, technical approval or installation.
Comparison
Approach Centreline Light vs Runway Centreline Light
| Feature | Approach Centreline Light | Runway Centreline Light |
|---|---|---|
| Primary function | Approach alignment and visual transition | Runway longitudinal guidance |
| Location | Extended runway centreline outside threshold | Runway pavement centreline |
| Typical colour | White / system specific | White, changing to alternating red/white and then red toward the runway end |
| Installation | Elevated/system-specific | Typically inset |
| Crossbars | Often associated | Not normally applicable |
| Sequenced flashers | May be included | Not normally |
| Main design driver | Approach category/system | Runway classification/operation |
Comparison
Approach Centreline vs Approach Crossbar Light
| Feature | Centreline | Crossbar |
|---|---|---|
| Main function | Longitudinal reference | Horizontal reference |
| Location | Extended centreline | Transverse to centreline |
| Visual information | Alignment | Roll/horizontal reference |
| Typical light | White | White |
| System role | Primary longitudinal element | Supporting geometric reference |
FAQ
Approach Centreline Light — Frequently Asked Questions
What does an approach centreline light do?
Approach centreline lights form the principal longitudinal visual reference of many approach lighting systems, extending outward from the runway threshold along the extended runway centreline. They assist with runway alignment, approach-path recognition, horizontal reference, the visual transition toward the runway, and runway orientation during night and reduced-visibility operations.
What does ICAO specify for approach centreline lights?
Annex 14 distinguishes simple and precision approach lighting systems. A simple system uses fixed centreline lights, each a single light source or a barrette at least 3 m long (1.5 m spacing between point sources has been found satisfactory), extending wherever possible not less than 420 m from the threshold, with a crossbar of 18 m or 30 m at 300 m. A Category I precision system has a centreline row on the extended runway centreline, wherever possible 900 m from the threshold, with the applicable crossbar arrangement. Verify the edition and amendments for each project.
What are FAA MALS, MALSF and MALSR approach lighting systems?
MALS is the Medium Intensity Approach Lighting System, MALSF is MALS with Sequenced Flashing Lights, and MALSR is MALS with Runway Alignment Indicator Lights. FAA describes MALSR as a combination of steady-burning light bars and sequenced flashers giving pilots runway alignment, height perception, roll guidance and horizontal references for the visual portion of an instrument approach.
What is the MALSR centreline arrangement?
The centreline has nine sets of five white steady-burning light sources: seven bars at 200 ft intervals and two offset bars associated with the 1,000-ft bar. The sequenced-flasher array has five white flashing lights at 200-ft intervals on the extended centreline. Take the exact configuration from the current approved FAA design and the applicable system drawing.
What is the difference between steady-burning centreline lights and sequenced flashers?
Steady-burning centreline lights provide continuous longitudinal and horizontal visual references, while sequenced flashers provide dynamic directional information that helps identify the approach path (MALSF, MALSR). The two functions are not interchangeable, so treat flasher equipment as a separate functional element even when supplied with the complete system, and coordinate flasher spacing and sequence, synchronization and flash rate, intensity and direction, and the control system.
What colour are approach centreline lights?
White is the principal colour for the centreline reference. ICAO selects colour so the approach system is readily distinguishable from other aeronautical ground lighting and extraneous lighting, and FAA MALSR uses white steady bars and white flashers with green threshold lighting. Verify the colour against the approach system type, runway threshold arrangement, applicable authority, project drawing and manufacturer configuration.
How are approach centreline lights powered?
The architecture is system-specific. It may include a constant-current supply, dedicated approach-lighting circuits, series-circuit supply with individual isolation transformers, local control equipment and sequenced-flasher control. Approach lighting may use electrical architectures different from runway and taxiway series circuits, so match the product to the specific approach lighting system and not to a runway centreline light.
Do approach centreline lights need to be frangible?
ICAO requires elevated approach lights and their supports to be frangible; beyond 300 m from the threshold, where a support is taller than 12 m, frangibility applies to the top 12 m only (Annex 14, Chapter 5, confirm against your edition). FAA guidance identifies low-impact-resistant support structures for approach-light installations. Installation may use elevated supports and towers, frangible or low-level supports, modular light bars, or flush arrangements where approved.
How does an approach centreline light differ from a runway centreline light?
An approach centreline light gives approach alignment and visual transition on the extended runway centreline outside the threshold, is typically white or system-specific, is usually elevated or system-specific, is often associated with crossbars, and may include sequenced flashers; its design driver is the approach category and system. A runway centreline light gives longitudinal guidance on the runway pavement centreline, changes from white to alternating red/white and then red toward the runway end, is typically inset, and is driven by runway classification and operation.
What are the common faults in approach centreline lighting?
Typical symptoms are a light that is off, low light output, incorrect alignment, an uneven centreline appearance, a flasher not operating and an inconsistent approach pattern. Troubleshoot in sequence: approach control system, CCR or power supply, primary circuit, transformer or local power, secondary connection, centreline fixture, light source, optical alignment and photometry. Where flashers are installed, check the sequencer, flasher controller, flasher circuit, individual flasher and synchronization.
What should be confirmed before ordering approach centreline lights?
Confirm the runway designation and threshold, approach category, approach lighting system, system length, centreline light-bar configuration, crossbar and side-row configuration, steady-burning and sequenced-flasher requirements, light colour, beam distribution, intensity steps, light spacing, support structure and frangibility, circuit and transformer arrangement, control interface, and the applicable standard. Request the datasheet, photometric report, centreline layout information, mounting drawing, frangibility information and compliance certificates.
Why Precision AGL Solutions
A Complete Approach Lighting System View
We consider approach centreline lighting part of the complete Approach Lighting System. Our approach considers:
Approach Category → System Type → Runway Centreline → Light Stations → Crossbars → Side Rows → Flashers → Optics → Supports → Power → CCR → Control → Photometry → Maintenance
This helps ensure the selected centreline equipment matches the approved approach-lighting configuration.
Procurement Information for Indian Projects
Indian public tenders commonly ask for the documents below. State which ones your tender requires when you send the enquiry, so they are covered in the quotation.
- Manufacturer / OEM authorisation
- Country of origin and local-content declaration (for Make in India purchase preference)
- Type-test and routine-test certificates, and the FAA / ICAO / IEC compliance documents named in the specification
- Datasheets, drawings and installation instructions
- Warranty, delivery period and spares support
- GeM catalogue or tender-portal requirements, where applicable
Request Approach-Lighting System Selection
Planning a new approach lighting system, runway upgrade or approach-lighting rehabilitation project? Submit your runway designation, threshold location, approach category, existing approach-lighting system, approved layout, centreline/light-bar and crossbar arrangement, flasher requirement, BOQ, technical specification, fixture quantity, electrical/control details and existing fixture information. Precision AGL Solutions can review the configuration and support selection of the appropriate centreline light, light-bar, optical arrangement, electrical interface and supporting technical documentation.
- Emailprecisionaglsolutions@gmail.com
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- Phone+91 98214 96412
Engineering Note
Approach centreline lighting is a system-level visual aid. The correct product cannot be selected by specifying “white approach light” alone.
Selection must consider approach category, system type, centreline geometry, spacing, crossbars, optical distribution, steady/flashing operation, support arrangement, control system and applicable photometric requirements. For FAA projects, identify the MALS/MALSF/MALSR configuration before product selection, as their centreline and sequenced-flasher arrangements differ.
Product Disclaimer
Product availability, configuration, dimensions, electrical characteristics, photometric performance, certifications and compliance status depend on the selected manufacturer and project specification. The technical values published on this page should not be treated as a substitute for the manufacturer's current approved Technical Data Sheet.
Final selection shall be based on the approved project specification, applicable aviation standards, authority requirements, manufacturer documentation and site conditions. Use of this page is also subject to the Legal Notice, Disclaimer & Terms of Use.
Standards and editions referenced on this site are listed on the Standards Reference page.