Approach Lighting
Approach Crossbar Light for Airfield Ground Lighting
Transverse visual reference across the approach centreline
Approach crossbar lights provide the transverse visual reference across the approach centreline, with project-specific optical, spacing, mounting and electrical configurations for precision and configured approach-lighting systems.
Supplied by Precision AGL Solutions
Product Overview
Approach Crossbar Light
What It Is
Approach crossbar lights form an important transverse visual reference within an airport approach lighting system. The centreline gives the principal longitudinal reference; crossbars extend across it to give a clear horizontal and lateral reference during approach.
Centreline + Crossbar + Side Row creates a geometric pattern for the pilot.
The Pattern Assists With
- Runway alignment
- Lateral position
- Roll perception
- Approach orientation
- Visual transition from instrument to visual flight
Selected According To
- Approach category and lighting system type
- Runway geometry and threshold position
- Centreline and side-row arrangement
- Crossbar location, length and fixture spacing
- Light colour, optical direction, intensity
- Mounting arrangement and support structure
- Electrical circuit and control requirements
- Project technical specification
The final crossbar configuration should be taken from the approved approach-lighting layout and applicable aerodrome standard.
Applications
Where Approach Crossbar Lighting Is Used
Simple approach systemsCentreline-associated crossbar.
Precision Category I30 m crossbar at 300 m.
Precision Category II / IIICrossbars at 150 m and 300 m.
Configured systemsSystem-specific.
MALS / MALSF / MALSRFAA medium-intensity.
ALSF-type systemsHigh-intensity.
Approach rehabilitationReplacement equipment.
Runway upgradesAirport projects.
New airport constructionNew installations.
ICAO uses crossbars at defined stations: for Category I, a 30 m crossbar at 300 m from the threshold; for Category II/III, crossbars at 150 m and 300 m.
Function
A Transverse Reference Across the Centreline
Helps the Pilot Interpret
- Horizontal position and runway alignment
- Roll attitude
- Approach geometry
- Perspective and distance
- Aircraft relationship to the centreline
Centreline + Crossbar
Centreline = longitudinal reference. Crossbar = transverse reference. Together: longitudinal guidance + horizontal reference. The crossbar is a geometric element, not simply an additional group of lamps.
ICAO Simple Approach
ICAO Simple Approach System
Geometry
Crossbar lights are arranged as nearly as practicable in a horizontal straight line at right angles to and bisected by the centreline.
Spacing
ICAO notes spacings of 1 m to 4 m are in use. With a 30 m crossbar, gaps may be provided either side of the centreline, each not exceeding 6 m.
Where sufficient centreline length cannot be physically achieved, ICAO provides for shortening the centreline while retaining the crossbar where practicable.
Precision Category I
Precision Approach Category I
ICAO Specifies
- Approach centreline extending wherever possible to 900 m from the threshold
- A 30 m crossbar
- Located 300 m from the threshold
Conceptual Layout
300 m ↔ runway threshold
The drawing is conceptual. The approved project drawing controls the actual geometry.
Precision Category II / III
Category II / III Crossbars
ICAO System
- Centreline row wherever possible 900 m
- Two side rows extending 270 m (240 m where serviceability is demonstrated)
- Crossbar at 150 m
- Crossbar at 300 m
Visual Geometry
The crossbars are an important part of the complete Category II/III visual geometry, working with side rows and centreline as one field.
150 m Crossbar
- ICAO: fills the gaps between centreline and side-row lights
- Completes the transverse reference close to the threshold
- Check against centreline spacing, side-row gauge, threshold location, TDZ gauge and side-row position
300 m Crossbar
The principal wider transverse reference. ICAO: extends on both sides of the centreline to 15 m from the centreline — a total nominal extent of approximately 30 m.
Crossbar Geometry
Geometry, Spacing and Length
Crossbar Lights Should Be
- As nearly as practicable in a horizontal straight line
- At right angles to the centreline
- Bisected by the centreline
- Spaced to produce a linear visual effect
Accurate survey and installation are important.
Spacing Is Determined By
- Crossbar length and number of light sources
- Fixture/barrette configuration
- Applicable approach system and authority requirement
- Approved project drawing
Do not present one universal spacing value for all approach systems.
| Application | Crossbar Arrangement |
|---|---|
| Simple approach system | 18 m or 30 m at 300 m from the threshold (ICAO) |
| Precision Category I | 30 m at 300 m |
| Precision Category II/III | 150 m crossbar + 300 m crossbar |
| Category II/III 300 m crossbar | 15 m each side of centreline |
| Other configured systems | System-specific |
The selected fixture/assembly must match the approved crossbar length and number of light sources.
Light Colour
Colour Depends on the Approach System
ICAO & FAA
For conventional ICAO systems the crossbar is part of the centreline/crossbar visual field and uses the applicable approach-system colour. Annex 14 specifies fixed white lights for the approach centreline and crossbars; side rows are red and threshold lights are green. For FAA systems the arrangement depends on MALS, MALSF, MALSR, ALSF-1, ALSF-2 or another approved configuration.
Example: FAA ALSF-2
High-intensity white approach lights, green threshold lights and red side-row lights.
Do not specify the crossbar only as a generic “white crossbar light” without identifying the complete approach-lighting system.
Optics & Photometry
Optical Configuration & Photometric Performance
Important Characteristics
- Fixed output and directional visibility
- Horizontal and vertical beam coverage
- Main beam axis and intensity
- Colour/chromaticity
- Uniformity across the bar
The crossbar should be perceived as one coherent transverse element.
Evaluate As a System
Approach crossbars are precision visual-aid equipment; photometric performance should be evaluated as part of the complete approach-lighting system.
| Parameter | Engineering Requirement |
|---|---|
| Light source | LED / approved technology |
| Colour | System specific |
| Operation | Steady / system-specific |
| Intensity | Standard / project specific |
| Beam distribution | System specific |
| Horizontal / vertical coverage | Applicable requirement |
| Optical axis | Critical |
| Chromaticity | Applicable standard |
| Light spacing | Project/system dependent |
| Crossbar length | System dependent |
| Photometric verification | Project dependent |
LED Light Source
LED Technology and Light-Bar Assemblies
Potential Advantages
- Long operating life
- Reduced lamp replacement and maintenance
- Stable colour and consistent output
- Controlled beam distribution
- Reduced energy consumption
- Improved monitoring compatibility
Replacement equipment for a retained lamp-based system should match the approved optical and electrical configuration. LED technology alone does not establish compliance.
Supplied As
- Individual light fixtures
- Light bar or multi-source barrette
- Modular LED assembly
- Combined centreline/crossbar component
- System-specific approach-light fixture
For ICAO simple systems, each centreline light may be a single source or a barrette of at least 3 m, with 1.5 m spacing satisfactory for point sources — simplifying future precision-system expansion.
System Relationships
Side Rows, TDZ, Centreline and Flashers
Side-Row Lighting
In Category II/III the crossbars and side rows work as a coordinated field: side rows give lateral, crossbars transverse, and the centreline longitudinal alignment.
TDZ Lighting
ICAO ties the gauge between the innermost side-row lights to the TDZ-light gauge. Review crossbar, side-row and TDZ arrangements together for gauge, alignment, threshold position, visual continuity and perspective.
Centreline
The crossbar is not designed independently. The centreline determines the crossbar station, bisecting point, light orientation and approach axis.
Sequenced Flashers
FAA ALSF-2 combines steady-burning elements with 15 sequenced flashers flashing from the outer approach area toward the threshold. Keep crossbar lights visually distinct from flashers, centreline, side-row and threshold lights.
Electrical Characteristics
System-Specific Architecture
Potential Arrangements
- Series-circuit supply or CCR-fed circuit
- Dedicated approach-light circuit
- Local transformer or LED driver
- Control cabinet
- Integrated flasher/control equipment where required
Technical Review Should Verify
- Operating current and power consumption
- Circuit voltage/current
- Transformer requirement and driver characteristics
- Cable interface
- Intensity control and monitoring
CCR → Primary Circuit → Isolating Transformer → Secondary Cable → Crossbar Light Assembly
A possible series-circuit arrangement. The actual arrangement must follow the approved approach-lighting system.
Intensity Control
Visually Balanced at Every Intensity
Depending on the project the system may provide high, medium, low and multiple intensity steps or system-specific control. All centreline, side-row and crossbar components should remain visually balanced at each applicable operating intensity.
Mechanical Installation
Supports, Plane and Environment
Crossbar Assemblies May Use
- Elevated or low-level supports
- Light bars and barrettes
- Frangible structures
- Modular support frames
Consider support height, horizontal alignment, frangibility, wind loading, structural stability, drainage, cable routing and maintenance access. FAA maintains a separate specification for Low-Impact Resistant (LIR) Structures. 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-Light Plane
ICAO requires the simple approach system to lie as nearly as practicable in the horizontal plane through the threshold, subject to obstacle and visibility provisions. Consider threshold, centreline and crossbar elevation, ground profile, support heights and the obstacle environment.
Environmental Exposure
- Rain, dust, humidity
- Temperature variation, UV, corrosion
- Wind, vibration, wildlife, maintenance activities
Installation Alignment
- Station from threshold and centreline reference
- 90-degree relationship to centreline
- Crossbar length, light spacing, elevation
- Optical direction, side-row relationship, support alignment
Even a small angular error can distort the perceived horizontal reference. For the Cat II/III 300 m crossbar, verify the specified extent on both sides.
Commissioning & Testing
Commission as Part of the Complete System
Visual & Electrical
- Fixture, lens, colour, crossbar straightness, position, spacing
- Centreline relationship, supports, frangibility, cables
- Continuity, insulation resistance, CCR output
- Transformer verification where applicable, connectors
- Intensity-step and control-system operation
Photometric & Geometry
- Colour, intensity, beam distribution, optical direction
- Crossbar uniformity and alignment
- Crossbar station and length
- 90-degree orientation, centreline bisecting point
- Side-row and TDZ relationship
Inspection & Maintenance
Optical, Mechanical, Electrical and Geometry
Optical & Mechanical
- Lens cleanliness and damage, light output, colour
- Beam direction and contamination
- Crossbar structure, supports, fasteners
- Frangibility, corrosion, alignment
Electrical & Geometry
- Cable, connector, transformer, CCR
- Control system and monitoring
- Station location and crossbar length
- Straightness, centreline and side-row relationship
Common Failure Modes
Symptoms and Possible Causes
| Symptom | Possible Causes |
|---|---|
| Crossbar light OFF | Circuit failure; LED/lamp failure; transformer fault; cable fault; connector failure; control-system problem |
| Uneven crossbar output | Mixed fixture outputs; LED degradation; lamp failure; optical contamination; incorrect intensity setting |
| Crossbar misalignment | Support movement; installation error; survey error; structural damage; foundation movement |
| Incomplete crossbar | Failed light sources; cable faults; missing fixture; damaged barrette; incorrect maintenance replacement |
| Poor horizontal reference | Incorrect station, orientation or crossbar length; uneven light output; missing light sources; centreline misalignment |
Engineering Troubleshooting Sequence
Use a Systematic Diagnostic Sequence
Approach lighting controlCommand
CCR / powerVerify
Primary circuitCheck
Transformer / driverCheck
Secondary connectionCheck
Crossbar fixtureCheck
Light sourceInspect
Optical alignmentInspect
Crossbar geometryVerify
PhotometryVerify
For system-level problems also verify: Centreline → Crossbar → Side Row → Threshold → TDZ.
Product Selection Matrix
Key Selection Parameters
| Selection Parameter | Requirement |
|---|---|
| Application | Approach lighting |
| Approach category | Simple / Cat I / Cat II / Cat III |
| System | ICAO / MALS / MALSF / MALSR / ALSF / project-specific |
| Crossbar station / length | System specific |
| Centreline | Extended runway centreline |
| Side rows | Where applicable |
| Light source | LED / approved technology |
| Colour | System specific |
| Operation | Steady / system-specific |
| Beam / Intensity | Project specific |
| Spacing | System dependent |
| Support | Elevated / low-level / bar assembly |
| Frangibility | Applicable |
| CCR / Transformer | Project specific / where applicable |
| Control / Monitoring | Project specific |
| Environment | Airport specific |
| Documentation | TDS / photometry / certificates |
Product Selection Checklist
Before Ordering, Confirm
- Airport / project
- Runway designation and threshold location
- Approach category
- Approach-lighting system type
- Centreline arrangement
- Crossbar station and length
- Number of light sources
- Individual-light spacing
- Side-row arrangement
- TDZ-light gauge
- Light colour
- Optical direction and beam distribution
- Intensity and intensity steps
- LED / approved light source
- Light-bar/barrette configuration
- Support structure and frangibility
- CCR / power supply
- Transformer requirement
- Cable arrangement
- 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
- Crossbar layout drawing
- Crossbar station information
- Crossbar length
- Light-spacing information
- Centreline interface
- Side-row interface
- Electrical specification
- Operating current
- Power consumption
- CCR compatibility
- Transformer requirement
- Connector details
- Mounting drawing
- Support-structure details
- Frangibility documentation
- Installation tolerances
- Cable-routing information
- Control/interface diagram
- Monitoring information
- Environmental rating
- Installation manual
- Maintenance manual
- Compliance certificates
- Type-test reports
- Warranty information
Standards & References
Governing Standards
ICAO
- Simple system: crossbar horizontal, at right angles to and bisected by the centreline; 1–4 m spacing noted
- Category I: 30 m crossbar at 300 m from threshold
- Category II/III: crossbars at 150 m and 300 m
- 150 m crossbar fills gaps between centreline and side rows
- 300 m crossbar extends 15 m each side of centreline
- 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). Check later amendments and corrigenda before procurement
FAA
FAA Order JO 6850.2C — Visual Guidance Lighting Systems (30 August 2022), installation criteria for approach lighting systems. Approach systems use system-specific combinations of centreline, crossbar, side-row, threshold lights and sequenced flashers. ALSF-2: white steady-burning lights, red side-row lamps, green threshold lights, sequenced flashers.
AC 150/5340-30J — Design and Installation Details for Airport Visual Aids (active); covers MALSF and other visual aids.
AC 150/5345-46F — airport light fixtures; exact approach-light fixture depends on the approved system.
AC 150/5345-45C — Low-Impact Resistant (LIR) Structures supporting approach lighting.
India — Also Verify
- DGCA requirements
- Airport-specific AGL specification
- Approved approach-lighting layout and approach category
- ILS/approach-system requirements
- PAPI coordination and TDZ-light arrangement
- Project BOQ and Employer’s requirements
- Applicable Indian Standards
- Airport operator requirements
Always verify the governing document edition and project-specific requirements before technical approval, procurement or installation.
Comparison
Approach Crossbar vs Approach Centreline
| Feature | Approach Crossbar | Approach Centreline |
|---|---|---|
| Primary function | Transverse reference | Longitudinal reference |
| Location | Perpendicular to centreline | Extended centreline |
| Main information | Horizontal/roll reference | Runway alignment |
| Typical operation | Steady/system specific | Steady/system specific |
| System role | Supporting geometry | Primary longitudinal reference |
| Key parameter | Crossbar station and length | Centreline station and length |
Comparison
Approach Crossbar vs Side Row
| Feature | Crossbar | Side Row |
|---|---|---|
| Primary function | Transverse reference | Lateral reference |
| Arrangement | Across centreline | Parallel to centreline |
| Typical Cat II/III colour | White (ICAO); system-specific (FAA) | Red |
| Main visual information | Horizontal reference | Lateral/roll reference |
| Relationship | Connected geometric reference | Connected geometric reference |
Comparison
Approach Crossbar vs Sequenced Flasher
| Feature | Crossbar | Sequenced Flasher |
|---|---|---|
| Operation | Normally steady | Sequential flashing |
| Primary function | Horizontal reference | Dynamic approach-path indication |
| Light pattern | Transverse | Moving sequence |
| Main design driver | Crossbar geometry | Flash sequence and timing |
| System role | Geometric reference | Lead-in/approach cue |
FAA ALSF-2 includes both steady-burning approach elements and sequenced flashers.
FAQ
Approach Crossbar Light — Frequently Asked Questions
What is an approach crossbar light?
Approach crossbar lights form a transverse visual reference within an approach lighting system. The centreline gives the principal longitudinal reference and the crossbars extend across it to give a clear horizontal and lateral reference. Together with the centreline and side rows they help the pilot judge runway alignment, lateral position, roll perception and approach orientation during the visual transition.
Where are approach crossbars located under ICAO?
For a simple approach system the crossbar is 18 m or 30 m long at 300 m from the threshold. For precision approach Category I it is a 30 m crossbar at 300 m from the threshold. For Category II/III there are crossbars at 150 m and 300 m. The approved project drawing controls the actual geometry.
How are crossbar lights arranged and spaced?
Crossbar lights are arranged as nearly as practicable in a horizontal straight line at right angles to and bisected by the centreline. ICAO notes spacings of 1 m to 4 m are in use, and with a 30 m crossbar gaps may be provided either side of the centreline, each not exceeding 6 m. Do not present one universal spacing value for all approach systems; it depends on crossbar length, number of light sources, the approach system and the approved drawing.
What do the 150 m and 300 m crossbars do in Category II/III?
The 150 m crossbar fills the gaps between the centreline and side-row lights and completes the transverse reference close to the threshold. The 300 m crossbar is the principal wider transverse reference: it extends on both sides of the centreline to 15 m from the centreline, a total nominal extent of approximately 30 m. Both work with the side rows and centreline as one visual field.
What colour are approach crossbar lights?
Annex 14 specifies fixed white lights for the approach centreline and crossbars, with red side rows and green threshold lights. For FAA systems the arrangement depends on MALS, MALSF, MALSR, ALSF-1, ALSF-2 or another approved configuration; ALSF-2 uses high-intensity white approach lights, green threshold lights and red side-row lights. Do not specify the crossbar only as a generic white crossbar light without identifying the complete approach lighting system.
How does a crossbar relate to the centreline, side rows and TDZ lights?
The crossbar is not designed independently: the centreline determines the crossbar station, bisecting point, light orientation and approach axis. In Category II/III the crossbars and side rows work as a coordinated field, with side rows giving lateral, crossbars transverse and the centreline longitudinal alignment. ICAO ties the gauge between the innermost side-row lights to the touchdown-zone light gauge, so review the crossbar, side-row and TDZ arrangements together.
How is a crossbar different from a sequenced flasher?
A crossbar is normally steady and provides a transverse, geometric horizontal and roll reference, while a sequenced flasher flashes in sequence and provides a dynamic lead-in cue along the approach path. FAA ALSF-2 includes both steady-burning approach elements and 15 sequenced flashers flashing from the outer approach area toward the threshold, so keep crossbar lights visually distinct from flashers, centreline, side-row and threshold lights.
How are crossbar lights supported and aligned?
Assemblies may use elevated or low-level supports, light bars and barrettes, frangible structures or modular support frames. 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), and the simple system lies as nearly as practicable in the horizontal plane through the threshold. Verify the station from the threshold and centreline reference, the 90-degree relationship to the centreline, crossbar length, spacing and elevation, because even a small angular error can distort the perceived horizontal reference.
How are crossbar lights powered and how is intensity controlled?
Potential arrangements include a series-circuit supply or CCR-fed circuit, a dedicated approach-light circuit, a local transformer or LED driver, a control cabinet and integrated flasher or control equipment where required. Depending on the project the system may provide high, medium, low and multiple intensity steps, and all centreline, side-row and crossbar components should remain visually balanced at each applicable operating intensity.
What are the common faults in approach crossbar lighting?
Typical symptoms are a crossbar light that is off, uneven crossbar output, crossbar misalignment, an incomplete crossbar and a poor horizontal reference. Troubleshoot in sequence: approach lighting control, CCR or power, primary circuit, transformer or driver, secondary connection, crossbar fixture, light source, optical alignment, crossbar geometry and photometry. For system-level problems also verify centreline, crossbar, side row, threshold and TDZ.
What should be confirmed before ordering approach crossbar lights?
Confirm the runway designation and threshold location, approach category, approach lighting system type, centreline arrangement, crossbar station and length, number of light sources and individual-light spacing, side-row arrangement, TDZ-light gauge, light colour, optical direction, intensity steps, light-bar or barrette configuration, support structure and frangibility, and electrical and control details. Request the crossbar layout drawing, photometric report, mounting drawing, frangibility documentation and compliance certificates.
Why Precision AGL Solutions
Part of the Complete Approach Lighting System
We treat the approach crossbar as part of the complete Approach Lighting System, not an isolated light assembly. Our approach considers:
Approach Category → System Type → Centreline → Crossbar → Side Row → TDZ Gauge → Optics → Supports → Electrical Circuit → Control → Photometry → Maintenance
This helps keep crossbar dimensions, position and optical output coordinated with the complete approach-lighting pattern.
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 Design Support
Planning a new approach lighting system, precision runway upgrade or approach-lighting rehabilitation project? Submit your runway designation, threshold location, approach category, existing approach-lighting system, approved layout, centreline arrangement, crossbar stations and lengths, side-row arrangement, TDZ layout, RVR requirement, BOQ, technical specification, fixture quantity, electrical/control details and existing fixture information. Precision AGL Solutions can review the approach layout and support selection of the appropriate crossbar fixture or light-bar configuration, optical characteristics, support arrangement, electrical interface and technical documentation.
- Emailprecisionaglsolutions@gmail.com
- Websiterahulsharmaagl.in
- LinkedInPrecision AGL Solutions
- Phone+91 98214 96412
Engineering Note
Approach crossbar lighting should be treated as a geometric component of the complete approach-lighting system.
For ICAO Category I, the key reference is the 30 m crossbar at 300 m from the threshold. For Category II/III, the principal crossbars are at 150 m and 300 m: the 150 m bar fills the gaps between centreline and side rows, and the 300 m bar extends 15 m on either side of the centreline.
For FAA projects, derive the crossbar configuration from the specified system (ALSF-2, MALSR or another approved system) rather than assuming one universal crossbar product applies to all approaches.
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.