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Safety-critical technical reference — read before use. Independent educational guidance for qualified AGL and aerodrome personnel. It is not an approved procedure, design, specification or regulatory instruction and does not replace your aerodrome’s permit-to-work, isolation/LOTO procedures, the approved design or the manufacturer’s instructions. Series-circuit AGL equipment can carry lethal voltages. Read the full disclaimer ↓
THE AGL ENGINEERING CENTRE by Precision AGL Academy · Runway Lighting Systems

Runway Lighting Systems

The visual guidance system that defines the runway environment. Runway lighting gives pilots the visual references needed for approach, identification, landing, takeoff and movement along the runway — built from fixtures, series circuits, Constant Current Regulators, isolation transformers, cables, connectors, control, monitoring and photometric performance working together as one integrated system.

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Overview

What Is a Runway Lighting System?

A runway lighting system is the coordinated arrangement of visual lighting aids installed along and around a runway to provide pilots with the visual information required for safe runway operations.

Depending on the runway configuration and applicable operational requirements, the system may include runway edge lights, centreline lights, threshold lights, end lights, touchdown zone lights, approach lighting, lead-on/lead-off lighting, runway guard lights, stop bars at associated taxiway intersections, illuminated signs and PAPI or other visual approach slope indicators. The exact combination depends on the runway type, operational category, airport configuration and applicable standards.

Not a Collection of Lights

Runway lighting is an integrated system of fixtures, series circuits, CCRs, isolation transformers, cables, connectors, control and monitoring, electrical infrastructure and photometric performance.

The Primary Visual Reference

The runway is the primary visual reference during critical phases of flight — approach, landing, takeoff and ground movement, especially during darkness or reduced visibility.

Serves the Pilot

Every element exists to answer the pilot's questions: where is the runway, where does it begin and end, where is the centreline, the edges and the touchdown area?

Why It Matters

Why Runway Lighting Is Important

The runway is the primary visual reference for aircraft during critical phases of flight. During darkness or reduced visibility, these visual references become especially important for a pilot to answer:

Where is the runway? Where does it begin? Where does it end? What is the centreline? What are the edges? Where is the touchdown area? What is my position relative to the runway?
The Complete Sequence

The Runway Lighting System at a Glance

A simplified runway lighting architecture shows an important concept: the runway light is only the final visible element of a much larger electrical and control system.

AIRPORT POWER SUPPLY
AGL CONTROL / SWITCHING
CONSTANT CURRENT REGULATOR (CCR)
SERIES CIRCUIT
ISOLATION TRANSFORMERS
RUNWAY LIGHT FIXTURES
OPTICAL OUTPUT
PILOT VISUAL GUIDANCE
Core Elements

Main Runway Lighting Elements

Runway Edge Lights

Define the lateral limits of the runway, providing pilots with visual information about the runway boundaries — particularly during night operations and reduced visibility.

Runway Centreline Lights

Provide longitudinal guidance along the runway centreline, particularly important on runways supporting operations requiring enhanced centreline guidance.

Runway Threshold Lights

Identify the beginning of the usable runway for a landing aircraft, providing an important visual transition between the approach environment and the runway.

Runway End Lights

Identify the end of the runway, with visual characteristics coordinated with the overall runway lighting system and applicable aerodrome standards.

Touchdown Zone Lights

Provide additional visual guidance in the runway touchdown area — associated with runways requiring enhanced visual guidance.

Stop Bars & Signs

Stop bars at associated taxiway intersections and illuminated signs support runway-protection and guidance functions around the runway environment.

SECTIONS · FOUR RUNWAY FIXTURES ELEVATED EDGE edge of the runway marks the runway edges white, seen along the runway raised on a frangible coupling INSET CENTRELINE runway centreline marks the runway axis white, colour-coded near the end flush, takes wheel loads INSET TOUCHDOWN touchdown zone marks the touchdown zone white, one direction flush, takes wheel loads THRESHOLD / END start and end of runway marks threshold and end green outward, red inward raised, frangible coupling
Figure 1. Edge, centreline, touchdown zone, threshold and end: four runway lights that differ in what they mark, how they are mounted, their colour and the direction of their light.AGL Visual Encyclopedia: Different runway fixtures
Before the Threshold

Runway Approach Lighting

Approach lighting provides visual guidance before the aircraft reaches the runway, creating a visual transition from the approach environment toward the runway threshold. Approach lighting should be considered as part of the overall runway visual guidance system.

Approach light bars Centreline elements Side elements Sequenced lighting Flashing elements Other associated visual aids
Simplified Approach Lighting Pattern

A centreline of light bars leads to the threshold, with a crossbar providing roll and distance cues before touchdown

Sequenced flashing lights (indicative) CROSSBAR Roll & distance cue THRESHOLD Wing bar Runway Approach direction — configuration and exact spacing vary by system type and category
Visual Information

Runway Lighting Colours & Pattern

Colour and position are both part of the visual information a pilot relies on. Different colours and combinations communicate different runway locations or functions — the exact requirements depend on the lighting function, runway location and applicable ICAO/FAA or project requirements.

Colour Communicates Function

  • Runway edge
  • Threshold
  • Runway end
  • Centreline
  • Touchdown zone
  • Approach systems

Position Is a Spatial System

  • Longitudinal spacing
  • Transverse position
  • Centreline location
  • Threshold & runway end
  • Touchdown zone & approach area
  • Taxiway intersections

A lighting fixture that is correctly powered but incorrectly positioned can still compromise the intended visual guidance.

Runway Lighting Colour Pattern — Plan View

Colour changes at the threshold, along the last part of the runway, and at the runway end signal different information to the pilot

THRESHOLD Green TOUCHDOWN ZONE White bars CENTRELINE — WHITE RED / WHITE Approaching runway end RED Last segment EDGE — YELLOW Caution zone near end RUNWAY END Red
Exact colours, transition points and applicability (e.g. TDZ, enhanced centreline) depend on the runway category and the applicable ICAO/FAA/project requirement — this diagram illustrates the general pattern concept only.
TOP VIEW — THE COMPLETE PATTERN (AIRCRAFT LANDING LEFT TO RIGHT) THRESHOLD + WING BARS: GREEN TDZ BARRETTES EDGE LIGHTS: WHITE EDGE: YELLOW CENTRELINE: WHITE RED / WHITE RED RUNWAY END ROW: RED FAR-END COLOUR ZONES — LAST 1000 M (INSTRUMENT RUNWAY) 900 M 600 M 300 M RUNWAY END CENTRELINE LIGHTS EDGE LIGHTS CENTRELINE: WHITE, THEN ALTERNATING RED AND WHITE, THEN RED. EDGE LIGHTS: YELLOW IN THE LAST 600 M OR ONE-THIRD OF THE RUNWAY, WHICHEVER IS LESS. SCHEMATIC: NOT TO SCALE. ZONE DISTANCES ARE MEASURED FROM THE RUNWAY END.
Figure 2. How the edge, threshold, touchdown zone, centreline and end lights fit together, and what their colours tell the pilot.AGL Visual Encyclopedia: What is the runway lighting pattern?
Colour Reference

Runway Light Colours: Edge, Centreline, Threshold, End & Touchdown Zone

A quick reference for runway light colour (color) by function. Exact transition points depend on the runway type and the applicable ICAO, FAA or project requirement.

LightColourWhat it tells the pilot
Runway edge lightsWhite; yellow in the final portion of an instrument runwayMarks the lateral limits of the runway, with yellow warning that the runway is running out
Runway centreline lightsWhite, then alternating red/white, then red toward the endMarks the runway axis; the colour change shows the distance remaining
Runway threshold lightsGreenIdentifies the start of the usable landing runway
Runway end lightsRedMarks the end of the usable runway
Touchdown zone lightsWhiteMarks the touchdown zone along the runway

Quick Answers

Runway centerline color: whiteRunway threshold color: greenRunway end light color: redRunway touchdown zone light color: whiteRunway edge: white (yellow near the end of instrument runways)

What Color Are Runway Edge Lights?

Runway edge lights are white. On an instrument runway they change to yellow over the final portion of the runway, which tells the pilot that the remaining runway is limited.

What Color Are Runway Centerline Lights?

Runway centerline lights are white for most of the runway, then alternate red and white, and finally become red over the last section before the runway end.

What Color Are Runway Threshold Lights?

Runway threshold lights are green when viewed from the approach side. The green threshold lights, wing bars and threshold marking together provide runway threshold identification.

Runway Distance Markers

Runway distance markers are normally signs that show the distance remaining. They complement the lighting colour changes and are separate from the runway lights themselves.

Runway Threshold Color

Runway threshold color is green. Threshold lights, and the wing bars at their ends, show green toward an approaching aircraft, while runway end lights are red. Together they let the pilot tell the start of the usable runway from its end.

Runway Threshold Light Spacing

Runway threshold lights are placed in a line across the runway at the threshold, spaced evenly between the runway edge light rows, with wing bars at the sides. The number of lights and their spacing depend on runway width and approach category, so take the values from Annex 14 or the applicable standard and the approved design.

WHAT EACH COLOUR MEANS, AND WHERE YOU SEE IT PLAN VIEW · LANDING LEFT TO RIGHT · ILLUSTRATIVE, NOT TO SCALE PAPI: WHITE ABOVE · RED BELOW OBSTACLE LIGHT: RED BEACON: WHITE / GREEN RUNWAY EDGE: WHITE CAUTION ZONE: YELLOW RUNWAY END: RED APPROACH LIGHTS: WHITE SIDE ROWS: RED (CAT II/III) CENTRELINE: WHITE → RED/WHITE → RED TOUCHDOWN ZONE: WHITE THRESHOLD + WING BARS: GREEN GUARD LIGHTS: YELLOW TAXIWAY EDGE: BLUE RUNWAY-SIDE CENTRELINE: GREEN / YELLOW STOP BAR: RED TAXIWAY CENTRELINE: GREEN WHITE THE RUNWAY ITSELF RUNWAY EDGE CENTRELINE TOUCHDOWN ZONE APPROACH · PAPI YELLOW CAUTION EDGE, FINAL ZONE GUARD LIGHTS INTERMEDIATE HOLDING ILS-AREA CENTRELINE GREEN GO · SAFE PATH RUNWAY THRESHOLD THRESHOLD WING BARS TAXIWAY CENTRELINE LEAD-ON LIGHTS RED STOP · DANGER RUNWAY END STOP BARS CENTRELINE LAST ZONE OBSTACLES · PAPI LOW BLUE TAXIWAY EDGE TAXIWAY EDGE LIGHTS NEVER ON A RUNWAY OMNIDIRECTIONAL WHITE = RUNWAY · YELLOW = CAUTION · GREEN = GO · RED = STOP · BLUE = TAXIWAY EDGE
Figure 3. Colour is the first thing a pilot reads on an airfield at night. White, yellow, green, red and blue each carry a fixed meaning, so the colour of a light says what kind of surface it marks and what to do next.AGL Visual Encyclopedia: What does each AGL colour mean, and where is it used?
Weather & Visibility

Runway Lighting Visibility: Fog, Snow, Rain & Wet Weather

Runway lighting visibility depends on more than the lamp. Intensity setting, colour, alignment, cleanliness and weather all decide how well a pilot sees the runway.

Runway Lighting Pilot Visibility

Pilot visibility of the runway lights depends on the intensity step, the beam direction and the condition of the optics. A fixture that is lit but dirty or misaligned gives the pilot less than the design intends.

Runway Lighting Fog

In fog and low visibility the pilot relies on the lights for guidance, so the correct intensity step, consistent output between fixtures and correct alignment matter most.

Runway Lighting Snow

Runway lighting in snow faces obscured fixtures from snow, ice and slush, and elevated fixtures can be damaged by snow-clearing operations. Clearing procedures protect both visibility and equipment.

Runway Lighting Wet Weather

In wet weather, water can enter fixtures, connectors and bases and lower insulation resistance. Good sealing and drainage are what keep runway lights working through heavy rain.

Runway Lighting Rain Testing

Runway lighting rain testing uses water spray or wet-condition checks, followed by insulation measurements, to show that seals and connectors keep water out after installation or repair.

Runway Lighting Visual Guidance

The visual guidance that runway lighting gives comes from colour, pattern, position and brightness working together. Weather reduces how much of that the pilot can see, which is why consistency matters.

A CLOSED LOOP lights and RVR depend on each other STEP LOGIC a gap stops flicker WHO DECIDES three modes, ATC can override RVR computer RVR in metres Step logic table + ATC CCR step lamp current Runway lights light output intensity feeds back into RVR needs hysteresis and delay and a safe fallback RVR picks the step, the step shapes the RVR 5 4 3 2 1 STEP brighten as RVR falls dim after clear improvement RVR (m) rising gap between the two paths thresholds set by the aerodrome MANUAL ATC selects the step ADVISORY system suggests, ATC accepts AUTOMATIC RVR drives the step ATC OVERRIDE always available choice of mode is an aerodrome and authority decision SIGNAL CHAIN RVR sensors + RVR computer ALCMS step logic + step table CCR brightness step + ATC override Runway lights output feeds RVR
Figure 4. How the RVR result is used to choose the brightness step of the runway lights — manual, advisory or automatic — and why the loop between the lights and the RVR needs hysteresis, an ATC override and a safe fallback.AGL Visual Encyclopedia: What is RVR-to-intensity-step control?
Core Concept

The Runway Lighting Series Circuit

Many runway lighting systems use series circuits, allowing multiple runway lights to operate as part of a controlled constant-current lighting circuit.

CCR
Series Cable
Isolation Transformer
Runway Light
Isolation Transformer
Runway Light
Return
SERIES LOOP · THE PRINCIPLE ONE LOOP · ONE CURRENT · EQUAL LIGHT CCR I FIXED OUT RTN I I I T1 SAME LIGHT T2 SAME LIGHT T3 SAME LIGHT T4 SAME LIGHT 1 THE CCR SENDS ONE CURRENT AROUND THE LOOP 2 THE SAME CURRENT PASSES EVERY LIGHT IN TURN 3 SAME CURRENT = SAME BRIGHTNESS THE PRINCIPLE ONE LOOP, ONE CURRENT LIGHTS CONNECTED END TO END THE RESULT EQUAL BRIGHTNESS WHATEVER THE POSITION OR CABLE LENGTH THE TRADE-OFF ONE BREAK STOPS THE LOOP SO THE LOOP MUST STAY COMPLETE SCHEMATIC · LOOP SHORTENED · NOT TO SCALE
Figure 5. Lights connected end to end on one loop with one current — so every light gives the same output.AGL Visual Encyclopedia: What is the AGL series circuit principle?
Electrical Core

CCR & Isolation Transformers

Constant Current Regulator

The CCR provides controlled current to the AGL series circuit and, depending on system design, may provide multiple intensity levels. A problem anywhere in the chain — CCR current, series-circuit performance, transformer operation or fixture output — can affect the final photometric performance.

Isolation Transformers

Isolation transformers electrically separate individual runway fixtures from the primary series circuit — series circuit → transformer primary → transformer secondary → runway fixture. Transformer selection must be coordinated with the associated fixture and the overall series-circuit design.

The Electrical Interface

Runway Lighting Connectors

AGL connectors provide the electrical interface between the series circuit, transformers and fixtures — typically a primary connector, secondary connector, plug, receptacle and connector kits. Connector integrity matters because poor connections can result in:

High resistance Intermittent operation Heating Leakage Circuit faults Fixture failure
Operation

Runway Lighting Control & Intensity

Runway lighting is controlled through the airport's AGL control architecture, and is generally operated at different intensity levels depending on operational and visibility conditions — the CCR provides different current settings to achieve different lighting intensities.

ON/OFF & Circuit Selection

Basic switching and circuit-level control.

Intensity Selection

Lower, medium and higher intensity current steps.

Remote Operation & Status

Remote control with status and fault indication.

Monitoring

Continuous monitoring coordinated with operational requirements.

Operations

Runway Lighting Intensity Steps, Remote Control, Monitoring & Redundancy

How runway lighting is operated, watched and protected against failure.

Runway Lighting Intensity Steps

The CCR output is set to discrete brightness steps, commonly three or five, chosen to match visibility and ambient light. Each step corresponds to a defined output current.

Runway Lighting Remote Control

Runway lighting remote control lets the tower or a control room select circuits and intensity steps. Runway lighting ALCMS is the control and monitoring system that normally provides this.

Runway Lighting Monitoring

Runway lighting monitoring reports circuit status, current and faults to the operator, so a failing circuit can be found early. See the ALCMS page.

Runway Lighting Redundancy & Reliability

Runway lighting redundancy comes from measures such as interleaved circuits, duplicate equipment and standby arrangements. Runway lighting reliability depends on the design, the maintenance and how quickly faults are found.

Runway Lighting Backup & Emergency

Runway lighting backup and runway lighting emergency supply arrangements, such as a standby generator or secondary source with automatic changeover, keep the lights running when the main supply fails.

Energy Saving, LED Conversion & Solar

Runway lighting energy saving comes from runway lighting LED conversion, lower load and using lower intensity steps when conditions allow. Runway lighting solar is generally used for temporary or remote strips rather than main instrument runways.

Runway Lighting ALCMS

The airfield lighting control and monitoring system (ALCMS) lets the tower or a control room switch runway lighting circuits, select intensity steps and see circuit status and faults. See the ALCMS page for how it works.

Runway Lighting Reliability

Runway lighting reliability depends on circuit redundancy, maintenance quality, available spares and how quickly faults are found through monitoring. It is judged against the aerodrome's serviceability requirements.

Runway Lighting Emergency

Runway lighting emergency arrangements keep the lights available when the main supply fails, usually through a standby generator or secondary source with automatic changeover. The changeover time required depends on the runway type and operation, so confirm it in the applicable standard.

Runway Lighting Energy Saving & Runway Lighting Solar

Runway lighting energy saving comes from LED conversion, lower connected load and using lower intensity steps when conditions allow. Runway lighting solar is generally used for temporary or remote strips rather than main instrument runways.

ALCMS-TO-RUNWAY · ONE ACTION, SEVERAL CIRCUITS CIRCUIT CCR LIGHTS STATUS ALCMS RUNWAY CONTROL APPROACH CCR THRESHOLD CCR RUNWAY EDGE CCR TOUCHDOWN ZONE CCR CENTRELINE CCR RUNWAY END CCR STATUS RETURNS FOR EACH CIRCUIT SELECT RUNWAY IN USE SET BRIGHTNESS FOR CONDITIONS CHECK EACH CIRCUIT REPORTS KEY POINT ONE OPERATOR ACTION DRIVES SEVERAL CIRCUITS — BUT STATUS IS CHECKED CIRCUIT BY CIRCUIT SCHEMATIC · CIRCUIT LIST VARIES WITH RUNWAY CATEGORY · NOT TO SCALE
Figure 6. One operator action reaches every runway lighting circuit through its own CCR — and each circuit reports its own status back.AGL Visual Encyclopedia: How does the ALCMS control the runway?
Installation & Alignment

Runway Light Installation, Aiming & Calibration

Correct installation and aiming decide whether a runway light delivers its design performance.

How Are Runway Lights Installed?

Runway lights are installed on a runway light base set into the pavement or ground, with cables routed to the base and the fixture mounted on it. Elevated lights typically use frangible couplings; inset lights sit flush in the pavement.

Inset Installation & Installation Depth

Runway inset light installation and runway light installation depth follow the manufacturer's drawings. Wrong depth can affect drainage, loading and how far the fixture sits above the surface.

What Is Runway Light Aiming?

Runway light aiming is setting the direction in which a fixture emits its beam, so that the main beam points where the pilot will be looking. Aiming is checked with alignment tools and then confirmed by measurement.

Beam, Vertical & Horizontal Angle

Runway light beam angle is the extent of the useful beam. The runway light vertical angle is the elevation of the beam axis, and the runway light horizontal angle is its aiming relative to the runway axis.

Runway Light Calibration

Runway light calibration covers the calibration of the aiming tools and photometric instruments, and resetting fixtures to the calibrated aim. See AGL Photometry for the measurement side.

Runway Lighting Drawing

A runway lighting drawing shows the layout, circuits, cable routes and base positions. Keeping as-built drawings up to date is essential for maintenance and fault finding.

Runway Light Beam Angle

Runway light beam angle is the angular spread of a fixture's useful beam. It is defined by the fixture's isocandela diagram, and different light types have different beam spreads, so install only the type specified for the position.

Runway Light Vertical Angle & Runway Light Horizontal Angle

The runway light vertical angle is the elevation of the beam axis above horizontal. The runway light horizontal angle is the aiming of the beam relative to the runway axis. Both are set at installation, re-checked after fixture replacement, and confirmed by measurement.

TOP VIEW — ROTATION (INSET CENTRELINE LIGHT) SIDE VIEW — TILT (ELEVATED EDGE LIGHT) ALIGNED pilot is in the beam SLIGHTLY ROTATED pilot is at the edge of the beam WELL ROTATED pilot misses the beam AIRCRAFT ON CENTRELINE LEVEL, AIMED pilot is in the beam TILTED UP beam passes over the pilot TILTED DOWN beam goes into the ground PILOT ON THE APPROACH PATH SCHEMATIC: ANGLES AND BEAM WIDTH EXAGGERATED
Figure 7. How precisely a runway light is rotated and tilted, and why a small error can move its beam off the pilot.AGL Visual Encyclopedia: What is fixture alignment?
Verifying Performance

Photometry, Electrical Testing & Mechanical Inspection

Electrical operation does not automatically mean the runway lighting is performing correctly. Electrical testing answers: is the system electrically healthy? Photometry answers: is the system providing the required optical performance? Both are important.

Electrical Testing

  • Cable continuity
  • Insulation resistance
  • Transformer testing
  • Connector inspection
  • Series-circuit & CCR testing
  • Current verification
  • Fault monitoring
  • Earthing/bonding verification

Mechanical Inspection

  • Fixture housing & lens
  • Optical surfaces
  • Mounting & alignment
  • Frangible components
  • Water ingress & corrosion
  • Fasteners & cable entry
  • Connector condition

A physically damaged or contaminated fitting can have reduced photometric performance even when its electrical circuit is functioning normally.

Testing

Runway Lighting Tests: Acceptance, Electrical, Insulation, Continuity & Test Report

The electrical and acceptance tests that sit alongside photometry and mechanical inspection.

TestPurposeNote
Runway lighting commissioning testConfirms the installed system works as designed before handoverSee AGL Installation & Commissioning
Runway lighting acceptance testFormal check against the specification for acceptance by the ownerWitnessed and recorded
Runway lighting electrical testConfirms the electrical condition of circuits and equipmentIncludes the tests below
Runway lighting insulation testChecks cable and equipment insulation, for example with a meggerValues per specification
Runway lighting continuity testConfirms the series circuit is continuous and correctly connectedRun before energising
Runway lighting circuit resistanceMeasures circuit resistance and compares it with the baselineA rising trend can show degraded connections
Runway lighting rain testingChecks water ingress protection under wet conditionsFollowed by insulation checks
Runway lighting test reportRecords all results, instruments used and the outcomeSigned and kept with the as-built record
Acceptable values and test methods come from the applicable specification and standard. Electrical tests do not replace photometry, which checks the optical performance of the same lights.

Runway Lighting Acceptance Test

A runway lighting acceptance test is the witnessed, formal check against the specification before the owner accepts the system. It brings together the electrical, photometric and functional results.

Runway Lighting Electrical Test

The runway lighting electrical test confirms the condition of circuits and equipment: insulation, continuity, circuit resistance and current. Run it on isolated, locked-out circuits and compare results with the specification.

Runway Lighting Insulation Test

The runway lighting insulation test checks the insulation of cables and equipment, typically with a megger, with the circuit isolated and the regulator disconnected. Test voltage and minimum values come from the specification.

Runway Lighting Continuity Test

The runway lighting continuity test confirms the series circuit is unbroken and correctly connected, and it is run before the circuit is energised.

Runway Lighting Test Report

A runway lighting test report records every result, the instruments used and their calibration, the date and the pass or fail outcome. Sign it and keep it with the as-built record.

SERIES CIRCUIT · COMMISSIONING TESTS WHOLE LOOP · CCR ISOLATED 1 · ISOLATE 2 · LOOP Ω 3 · INSULATION 4 · ENERGISE ISOLATING TRANSFORMER + FIXTURE, ALL IN SERIES TXTXTXTX CCR ISOLATED LOCKED OFF OUTPUT DISCONNECTED LOW-RESISTANCE OHMMETER Ω INSULATION TESTER MΩ EARTH CLAMP AMMETER (ENERGISED STEP) SERIES LOOP (PRIMARY CABLE) LOOP RESISTANCEcompare with the design value INSULATION TO EARTHwhole loop, high and steady CURRENT AT EACH STEPstart on the lowest step NEVER OPEN A LIVE LOOPisolate and prove dead first SCHEMATIC · NOT TO SCALE · LIMITS COME FROM THE DESIGN, THE CCR DATA AND THE SPECIFICATION
Figure 8. A series circuit is proved as a whole loop, after its cables, connectors and transformers have been tested one by one. With the CCR isolated, the loop is checked for resistance and for insulation to earth, then brought up step by step while the current is read at each step.AGL Visual Encyclopedia: How is a series circuit tested before it is energised?
Interactive · Troubleshooting

Common Runway Lighting Faults

This is where the runway lighting system connects directly with the AGL Troubleshooting Engine. Tap a symptom to see possible causes.

One Runway Light OFF

Possible Causes

  • Fixture
  • Transformer
  • Connector
  • Secondary connection

Multiple Lights OFF

Possible Causes

  • Series circuit
  • CCR
  • Cable
  • Common connection

Entire Circuit OFF

Possible Causes

  • CCR
  • Circuit cable
  • Protection fault
  • Control fault

Low Intensity

Possible Causes

  • Fixture degradation
  • Optical contamination
  • Electrical problem

Flickering

Possible Causes

  • Loose connection
  • Transformer issue
  • Fixture issue
  • Circuit issue

Incorrect Colour

Possible Causes

  • Optical component fault
  • LED/module problem

Water Inside Fitting

Possible Causes

  • Seal failure
  • Damaged housing
  • Installation issue

Correct Test, Poor Output

Possible Causes

  • Optical problem
  • Alignment problem
Safety & Failures

Runway Lighting Safety, NOTAM, Outages & Failures

Working on runway lighting and handling failures both need controlled procedures.

Runway Lighting Electrical Safety

Runway lighting electrical safety starts from the fact that series circuits carry constant current at potentially dangerous voltage. Circuits must be isolated, locked out, tagged and earthed per procedure before work, and an energised series circuit must never be opened.

Runway Lighting Work Permit

A runway lighting work permit controls access to the airside, isolation of circuits and coordination with air traffic control before any work begins, and confirms the circuit is safe to work on.

What Is Runway Lighting NOTAM?

A runway lighting NOTAM is a notice to airmen announcing that runway lighting is unserviceable, restricted or being worked on. It is issued through the aerodrome's NOTAM process so pilots know what lighting is available.

What Happens When Runway Lighting Fails?

When runway lighting fails, the effect depends on how much is out. Aerodrome serviceability criteria limit how many lights may be unserviceable. Beyond those limits, operations may be restricted, a NOTAM is issued, and night or low-visibility operations may be suspended until it is restored.

Runway Light Not Working & Runway Lighting Outage

A runway light not working may be a lamp, transformer, connector, cable or CCR problem, and a runway lighting outage affects a whole circuit. Fault finding starts from the circuit status and current. See the troubleshooting engine.

AAI Runway Lighting

The Airports Authority of India (AAI) operates a large share of Indian airports. AAI runway lighting is specified and maintained in line with ICAO Annex 14 as implemented through DGCA regulation and AAI's own technical specifications.

DUTY CCR · STANDBY CCR · ONE CHANGEOVER SWITCH 1 · DUTY CCR HEALTHY SWITCH ON A · STANDBY IDLE CCR A STANDBY CHANGEOVER SWITCH SERIES CIRCUIT 2 · DUTY CCR FAILED CIRCUIT DARK UNTIL CHANGEOVER CCR A STANDBY CHANGEOVER SWITCH SERIES CIRCUIT 3 · ON STANDBY A ISOLATED · STANDBY CARRIES CIRCUIT CCR A STANDBY CHANGEOVER SWITCH SERIES CIRCUIT WHAT TO CHECK 1 SAME RATING same power, same brightness steps 2 BREAK BEFORE MAKE never two CCRs on one circuit 3 DE-ENERGISE FIRST switch only with the circuit off 4 TEST THE STANDBY run it on a circuit, not just on paper SCHEMATIC · ONE CIRCUIT SHOWN · NOT A SWITCHING PROCEDURE
Figure 9. A spare regulator and a changeover switch, so a failed CCR costs a short interruption instead of a dark circuit until the repair.AGL Visual Encyclopedia: What is a standby CCR and changeover arrangement?
Four Areas

Runway Lighting Maintenance

A strong maintenance program goes beyond simply replacing failed lights — it should consider four areas together.

Electrical

Check the condition and performance of the electrical system.

Mechanical

Inspect fixtures, mounting, housing, seals and physical condition.

Optical

Evaluate lenses, reflectors, LEDs and other optical elements.

Photometric

Measure actual lighting performance where required.

ONE VISIT · ORDER OF WORK live look first, hands-on work only when isolated THE PLAN · FREQUENCY LAYERS quick checks often, deeper tests less often CIRCUIT LIVE look and report defects noted ISOLATED, PROVED DEAD clean, inspect tighten, replace test RESTORED re-energise verify lights record OUTAGE KEPT SHORT · TASKS GROUPED UNDER ONE ISOLATION FREQUENT walk-round, lights-out check PERIODIC cleaning, inspection, torque LONGER INTERVAL insulation, earth, CCR service TIME → INTERVALS SET BY THE SITE PROGRAMME, REGULATOR AND MAKER RECORDS AND TRENDS FEED THE NEXT PLAN SIX VISIT STEPS · IN ORDER 1 PLAN programme, permit, parts, tools; agree access and outage 2 LOOK circuit live: walk the lights, note what is wrong 3 ISOLATE circuit off, locked out, proved dead before hands-on 4 SERVICE clean, inspect, tighten, replace worn parts 5 TEST insulation, continuity and earthing before re-energising 6 RESTORE, LOG re-energise, verify lights, record and trend the results
Figure 10. The planned order of work on a scheduled visit — plan and permit, look while live, isolate, clean, inspect and test, then restore, verify and record, so wear is found and fixed before a light fails.AGL Visual Encyclopedia: What is the preventive maintenance sequence?
Verification Sequence

Runway Lighting Commissioning

Commissioning should verify that the installed system corresponds with the approved design.

INSTALLATION
VISUAL INSPECTION
ELECTRICAL TESTING
CCR TESTING
SERIES CIRCUIT VERIFICATION
FIXTURE VERIFICATION
PHOTOMETRY
CONTROL & MONITORING VERIFICATION
OPERATIONAL TESTING
COMMISSIONING & FINAL DOCUMENTATION
COMMISSIONING SEQUENCE · IN WHAT ORDER PASS · RECORD · HOLD · THEN THE NEXT STAGE 1 PRE-COMMISSION Installation checked Circuit tests done Records ready HOLD: ready to energize 2 ENERGIZATION Controlled switch-on Steps raised in turn Readings watched HOLD: stable on all steps 3 FUNCTIONAL Each light and control Steps and alarms Local and remote HOLD: works as designed 4 INTEGRATION Circuits run together Interlocks proven Fault behaviour HOLD: system agrees 5 ALCMS LINK Control signals Status feedback Failure handling HOLD: command = response 6 PAPI Aiming and settings Glide path angle Flight check if required HOLD: angles confirmed 7 SIGNS Legends correct Brightness steps Control and status HOLD: signs correct 8 ACCEPTANCE Records reviewed Key tests witnessed Certificate signed HOLD: owner accepts A STAGE FAILS CORRECT · RE-TEST · REPEAT ALL EIGHT PASSED READY FOR SERVICE SCHEMATIC · STEPS SHORTENED · NOT TO SCALE
Figure 11. The planned order for bringing an AGL system into service — each stage passed and recorded before the next begins.AGL Visual Encyclopedia: What is the commissioning sequence?
Design Coordination

Runway Lighting Design Considerations & System Compatibility

When designing a runway lighting system, engineers need to coordinate runway classification, operational requirements, applicable standards, fixture type and spacing, circuit configuration, CCR capacity, transformer ratings, cable selection, control, monitoring, earthing, installation and maintenance access. The final design should be treated as an integrated electrical and visual system.

A Runway Lighting System Is Made of Interconnected Components

CCR
Series Cable
Isolation Transformer
Connector
Runway Fixture

Changing one component may affect the rest of the system — component compatibility should be checked before replacement or modification.

Modern Systems

LED Runway Lighting

Modern AGL systems increasingly use LED technology, offering benefits — but LED does not eliminate the need for electrical testing, mechanical inspection, optical inspection and photometry.

Long Operating Life

Lower energy consumption and reduced lamp replacement requirements.

Reduced Maintenance

Consistent optical performance when properly designed.

Still Needs Verification

LED fixtures can still degrade, become contaminated, misalign or fail electronically.

Documentation

Runway Lighting Documentation

Good documentation makes future maintenance and troubleshooting significantly easier.

Lighting Layout

Circuit drawings and single-line diagrams.

Cable & Transformer Schedules

Fixture, transformer and CCR schedules.

BOQ & Technical Specifications

Sign schedule and procurement documentation.

Test & Photometry Reports

Electrical and photometric verification records.

Commissioning Records

As-built drawings and final sign-off documentation.

Maintenance Documentation

Ongoing records supporting future maintenance work.

Fundamentals

Runway Lights Meaning, Types, Functions & Working Principle

Runway Lights Meaning

Runway lights meaning comes from colour and pattern: white edge and centreline lights show the usable runway, green marks the threshold, red marks the runway end, and yellow or alternating red-white lights warn how much runway remains.

Runway Lights At Night

Runway lights at night are the pilot's main reference for the runway's edges, centre, start and end. Intensity is set to suit visibility so the lights are clear without dazzling the pilot.

Runway Lighting System Components

Runway lighting system components are the light fixtures, isolation transformers, series cable and connectors, constant current regulators, and the control and monitoring system, supported by power supply and earthing.

Runway Lighting Types

Runway lighting types include edge, centreline, threshold, runway end and touchdown zone lights, with approach lights leading in. Fixtures are elevated (frangible) or inset in the pavement, in white, green, red or yellow by position.

Runway Lighting Functions

Runway lighting functions are to show the runway edges, give alignment and distance guidance along the centreline, mark the threshold and end, and show the touchdown zone, so the pilot can land, roll out and take off safely.

Runway Lighting Working Principle

Runway lighting working principle: a constant current regulator drives one fixed current round a series loop, and each light is fed by an isolation transformer. Changing the regulator's current step changes the brightness of every light on the circuit together.

LANDING DIRECTIONTHRESHOLD LIGHTS+ WING BARSRUNWAY END LIGHTSEDGE LIGHTS · 60 m MAX SPACINGRUNWAY CENTRELINE LIGHTSTOUCHDOWN ZONE LIGHTSTOUCHDOWN ZONE · FIRST 900 mCENTRELINE LIGHT COLOUR · RED/WHITE 900–300 m, RED LAST 300 mWHITERED / WHITEREDEDGE LIGHT COLOUR (SEEN FROM THE APPROACH)WHITEYELLOW · LAST 600 mPLAN VIEW · ILLUSTRATIVE, NOT TO SCALE · 3000 m RUNWAY SHOWN
Figure 12. Edge, threshold, touchdown zone, centreline and end lights each have a fixed place, spacing and colour along the runway.AGL Visual Encyclopedia: How are runway lights laid out?
Operations

Runway Lighting Intensity Levels, Runway Visual Range & Operations

Runway Lighting Intensity Levels

Runway lighting intensity levels are the brightness steps selected on the constant current regulator, commonly three or five. Higher steps suit poor visibility or bright daylight and lower steps suit clear nights; confirm the step table in the applicable standard.

Runway Visual Range Lighting

Runway visual range lighting links the measured RVR, the distance over which a pilot can see runway lights or markings, to the intensity step selected. Lower RVR calls for higher intensity, and RVR limits also decide which lighting systems low-visibility operations need.

Runway Lighting Operations

Runway lighting operations cover switching circuits on and off, selecting intensity, monitoring status and faults, and coordinating outages with air traffic control, normally through the ALCMS at the tower or control room.

Portable Runway Lighting

Portable runway lighting is a temporary, usually battery or solar powered set of lights used at temporary strips, during works or after damage. It supplements rather than replaces permanent AGL, and use needs regulator approval.

Edge Lights

Runway Edge Lights: Working Principle, Types, Design & Standards

Runway Edge Lights Working Principle

Runway edge lights working principle: each fixture is powered through its own isolation transformer on the runway series circuit, so a failed lamp does not break the loop. The CCR sets the current, which sets the brightness.

Runway Edge Lights Types

Runway edge lights types are elevated fixtures on frangible couplings, and inset fixtures where elevated lights are impractical. They are white, with yellow over the last part of an instrument runway, and use halogen or LED sources.

Runway Edge Lights Functions

Runway edge lights functions: define the lateral limits of the usable runway so the pilot can judge alignment and width, and through the yellow zone, the remaining runway length.

Runway Edge Lights Components

Runway edge lights components are the lamp or LED module, optical assembly and lens, fixture body, frangible coupling or inset housing, isolation transformer, connectors and base can.

Runway Edge Lights Specification

Runway edge lights specification covers photometric output, colour, mounting height, frangibility and ingress and impact protection, taken from the applicable standard (for example ICAO Annex 14 or FAA AC 150/5345-46) and the project specification.

Runway Edge Lights Design

Runway edge lights design fixes the spacing, which ICAO limits to 60 m on an instrument runway and 100 m on a non-instrument runway, the lateral position, the yellow zone and the circuit split.

Runway Edge Lights Maintenance

Runway edge lights maintenance includes cleaning lenses, checking aim and level, replacing failed lamps, inspecting frangible couplings and connectors, and recording serviceability.

Runway Edge Lights Testing Procedure

Runway edge lights testing procedure combines insulation resistance and continuity tests, current checks at each brightness step, a visual night check and, where required, photometric measurement.

Runway Edge Lights Selection Guide

Runway edge lights selection guide: choose elevated or inset, halogen or LED, and the colour and beam for the runway category, then match the fixture to the transformer and circuit load.

Runway Edge Lights Technical Guide

Runway edge lights technical guide: read it with the manufacturer datasheet, the aerodrome's standards and the circuit design to verify beam, colour, spacing and electrical data before installation.

Runway Edge Lights Standards

Runway edge lights standards include ICAO Annex 14 Volume I for location and characteristics, FAA AC 150/5345-46 for fixtures, AC 150/5340-30 for installation, and national rules such as DGCA requirements in India.

Runway Edge Lights Commissioning

Runway edge lights commissioning confirms position, aim, colour, circuit current at every step and tower control, with results recorded in the commissioning report.

APPROACH / TAKEOFF DIRECTION RUNWAY THRESHOLD RUNWAY END EQUAL SPACING RUNWAY EDGE LIGHTS RUNWAY WIDTH TWO PARALLEL ROWS, EQUIDISTANT FROM CENTERLINE · RUN THE FULL RUNWAY LENGTH
Figure 13. A longitudinal row of lights on each side of a runway that defines its lateral limits and provides continuous visual guidance along its length.AGL Visual Encyclopedia: What are runway edge lights?
Centreline Lights

Runway Centreline Lights: Working Principle, Types, Installation & Standards

Runway Centreline Lights Working Principle

Runway centreline lights working principle is that of the runway series circuit: inset fixtures each fed by an isolation transformer from the CCR, often split across alternate circuits so one circuit failure leaves every other light on.

Runway Centreline Lights Types

Runway centreline lights types are inset, in-pavement fixtures, unidirectional or bidirectional, white and red where the colour code calls for it, built to take aircraft wheel loads.

Runway Centreline Lights Functions

Runway centreline lights functions: give directional guidance during landing roll and take-off and, through the white, alternating red-white and red zones, show distance remaining.

Runway Centreline Lights Components

Runway centreline lights components are the inset fixture with lens and colour filter, light source, base can or shallow base, isolation transformer, cable and connectors.

Runway Centreline Lights Specification

Runway centreline lights specification covers photometry, colour, load rating, surface temperature limits and sealing against water, with values taken from the standard and the manufacturer's certification.

Runway Centreline Lights Design

Runway centreline lights design sets the spacing, colour zones along the runway, circuit arrangement and alignment with the runway axis, and depends on runway category and take-off visibility limits.

Runway Centreline Lights Installation

Runway centreline lights installation needs an accurate survey of the axis, correct base depth, flush fitting, sealed cable entries and correct fixing torque. Check aim after fitting, because inset lights are hard to adjust once the pavement is surfaced.

Runway Centreline Lights Maintenance

Runway centreline lights maintenance focuses on lens cleaning, removing rubber and tyre deposits, checking seals and bases, and replacing damaged fixtures, since landing traffic wears these lights fastest.

Runway Centreline Lights Testing Procedure

Runway centreline lights testing procedure includes circuit insulation and continuity tests, current at each step, light output and aim checks, and a night inspection for dark or misaligned lights.

Runway Centreline Lights Selection Guide

Runway centreline lights selection guide: choose by runway category, unidirectional or bidirectional pattern, colour filters, source (LED or halogen) and load rating for the aircraft using the runway.

Runway Centreline Lights Technical Guide

Runway centreline lights technical guide: check spacing, colours and photometric data against the design and standard, then confirm installation and wiring details on the manufacturer drawing.

Runway Centreline Lights Standards

Runway centreline lights standards sit in ICAO Annex 14 Volume I, which requires them on CAT II and III precision runways, and in FAA AC 150/5340-30 and AC 150/5345-46 for design and fixtures.

Runway Centreline Lights Commissioning

Runway centreline lights commissioning proves position along the axis, colour sequence, aim, circuit current at all steps and tower control before the runway is released for use.

LANDING ROLLOUT DIRECTION ◄ CONTINUES TOWARD THRESHOLD (WHITE ZONE — NOT SHOWN) RUNWAY EDGE LIGHTS (SECONDARY) RUNWAY END RED/WHITE ALTERNATING — LAST 900 M RED ONLY — LAST 300 M ALTERNATING ZONE RED ZONE RUNWAY CENTRELINE LIGHTS — FINAL ZONE RUNWAY WIDTH ZOOMED VIEW OF THE FINAL APPROACH ZONE ONLY · ROUND FLUSH-MOUNTED FIXTURES · NOT TO SCALE
Figure 14. A longitudinal line of lights installed along the runway centreline to provide precise directional guidance during takeoff, landing, and rollout.AGL Visual Encyclopedia: What are runway centreline lights?
Threshold, End & Touchdown

Threshold Lights, Runway End & Touchdown Zone Lighting Design

Threshold Lights Working Principle

Threshold lights working principle: green fixtures, on their own series circuit or shared with other runway lights, are driven by the CCR through isolation transformers and show arriving aircraft the start of the usable runway.

Threshold Lights Types

Threshold lights types are elevated or inset, green toward the approach, including combined threshold and end fixtures that show green to arriving aircraft and red to aircraft on the runway.

Threshold Lights Functions

Threshold lights functions: identify the beginning of the runway for landing, outline the runway width with wing bars where provided, and give a clear reference for where the runway can be used.

Threshold Lights Components

Threshold lights components include the green lens or filter, light source, fixture body or inset housing, isolation transformer, base and connectors, with wing bar lights added where required.

Threshold Lights Specification

Threshold lights specification covers green chromaticity, intensity toward the approach, mounting and frangibility. Use the applicable standard and fixture datasheet to confirm each value.

Threshold Lights Requirements

Threshold lights requirements depend on runway type and category. ICAO Annex 14 sets where they are needed, their colour, and the number and arrangement of lights across the threshold; check the current edition and national rules.

Threshold Lights Design

Threshold lights design sets the line of fixtures across the threshold, symmetry about the centreline, any wing bars, and how the circuits are arranged and shared.

Threshold Lights Installation

Threshold lights installation needs the line set square to the runway axis at the correct threshold position, with green fixtures aimed toward the approach and matching bases and cables.

Threshold Lights Maintenance

Threshold lights maintenance covers lens cleaning, aim and colour checks, lamp or LED replacement and connector inspection, with fast repair because a dark threshold weakens the pilot's reference.

Threshold Lights Troubleshooting

Threshold lights troubleshooting starts with the symptom: one light out points to the lamp, transformer or connector, while a group out suggests a cable fault, the circuit or the CCR. Measure current and insulation resistance to narrow it down.

Threshold Lights Testing Procedure

Threshold lights testing procedure checks insulation resistance, continuity, current at each intensity step, colour and aim, then confirms from the tower that the threshold circuit switches correctly.

Threshold Lights Selection Guide

Threshold lights selection guide: pick elevated or inset fixtures, plain or combined threshold/end units, and LED or halogen sources, matching colour, intensity and load to the circuit.

Threshold Lights Technical Guide

Threshold lights technical guide: use it with manufacturer drawings and the standard to verify position, count, colour and wiring of the threshold line before installation and testing.

Threshold Lights Standards

Threshold lights standards include ICAO Annex 14 Volume I for position and colour, FAA AC 150/5340-30 and AC 150/5345-46 for design and fixtures, and national requirements such as DGCA rules.

Threshold Lights Commissioning

Threshold lights commissioning confirms position, green colour, aim, circuit current and tower control, and records the results in the commissioning report.

Runway Threshold Lighting Design

Runway threshold lighting design sets the threshold line, wing bars and their relation to approach lights and markings. For a displaced threshold the lights must be adapted to match, so follow the standard for displaced thresholds.

Runway End Lighting Design

Runway end lighting design places red fixtures across the runway end, facing the runway, so they show red to aircraft rolling out and, with the threshold lights, mark both ends of the runway.

Runway Touchdown Zone Lighting Design

Runway touchdown zone lighting design uses rows of white barrettes either side of the centreline in the first part of the runway. ICAO requires them on CAT II and III precision runways; spacing and length follow the standard.

Runway Distance Remaining Signs

Runway distance remaining signs show the distance left to the runway end, in thousands of feet in FAA practice. They are lit signs beside the runway, and whether they are provided depends on the aerodrome's rules.

Runway Designation Markings And Lights

Runway designation markings are painted numbers at the threshold, not lights. At night they are seen in aircraft landing lights, so AGL design should coordinate threshold lights, markings and any lit signs.

PLAN VIEW · THE RUNWAY END EDGE LIGHTS ≥ 10 m ≥ 10 m WING BAR WING BAR THRESHOLD ROW · GREEN ≤ 3 m between lights (precision) WING BARS RUN OUTWARD FROM THE EDGE LINES WHAT TO CHECK 1 THRESHOLD ROW green, at the end, within 3 m outside 2 SPACING about 3 m or less on precision runways 3 WING BARS 5+ lights, 10 m+ outward 4 NON-PRECISION at least six lights in the row SCHEMATIC · NOT TO SCALE · LIGHT COUNT SHOWN IS NOT A DESIGN
Figure 15. A green row across the runway end, with a wing bar either side reaching at least 10 m outward.AGL Visual Encyclopedia: How are threshold and wing bar lights spaced?
Design & Standards

AGL Design for New Runway, ICAO Requirements & Selection Guide

AGL Design For New Runway

AGL design for a new runway starts with the runway category, then selects light types and layout from the standard, designs series circuits, sizes CCRs and cables, plans control and standby power, and ends with photometric checks and drawings.

Runway Lighting ICAO Requirements

Runway lighting ICAO requirements are in Annex 14 Volume I, Chapter 5, which sets which lights each runway type needs with their colour, intensity and spacing, plus electrical (Chapter 8) and maintenance (Chapter 10) provisions. Check the current edition.

Runway Lighting Selection Guide

Runway lighting selection guide: match fixture type, light source, colour and intensity to the runway category, pavement, climate and maintenance capability, then check compatibility with transformers and regulators.

Runway Lighting Technical Guide

Runway lighting technical guide: this page links design, circuits, photometry, testing and maintenance, and should be read with the aerodrome's standards, manufacturer data and the project specification.

Runway Lighting Testing Procedure

Runway lighting testing procedure covers insulation resistance, continuity, current at every step, earthing, aim and photometric checks, and control and monitoring tests, as set out in the Runway Lighting Tests section.

Runway Lighting Preventive Maintenance

Runway lighting preventive maintenance is the scheduled programme of inspection, cleaning, electrical tests, aim checks and replacement of worn parts, which keeps lights within serviceability limits and cuts unplanned outages.

SELECTION FLOWCHART · FOUR DECISIONS IN ORDER 1POSITION Where does the light sit? Centreline, TDZ, stop bar → INSET (in pavement) Edge, threshold, end → ELEVATED, or inset by layout 2DIRECTION Who must see it? One approach direction → UNIDIRECTIONAL Both directions → BIDIRECTIONAL 3INTENSITY What visibility is needed? Low-visibility operations → HIGH intensity Standard operations → MEDIUM or LOW intensity 4SOURCE What source and circuit? LED source → Lower load, long life Lamp (halogen) source → Like-for-like fit CONFIRM BEFORE ORDERING isocandela and colour · circuit current and transformer · frangibility or load rating FLOWCHART · THE MANUFACTURER DATA SHEET AND STANDARD DECIDE THE FINAL CHOICE
Figure 16. Four decisions, taken in order, that narrow the choice to the right type of runway light.AGL Visual Encyclopedia: How is a runway fixture selected?
Keyword Reference

Runway Lighting Installation, Approach Lights, LED Runway Lights & Threshold Lights Spacing

Runway lighting installation

Runway lighting installation is the physical work of placing the fixtures, transformers, cables and connectors for a runway and connecting them to the CCRs. It follows the approved drawings and the manufacturer's instructions, with checks at each stage before the circuit is energised. See Runway Light Installation, Aiming & Calibration above.

Approach lights runway

Approach lights runway is the common search phrase for the lighting that leads the pilot to the runway threshold. The approach lighting system sits on the extended centreline before the runway and works together with the threshold and runway lights. See Runway Approach Lighting above, and the Approach Lighting Systems page for the full detail.

LED runway lights

LED runway lights use LED light sources in edge, centreline, threshold and other runway fixtures. They offer lower power use and long life, but they must still meet the required photometric performance and work correctly with the series circuit and CCR. Compatibility and approval should be confirmed before replacing existing fixtures. See LED Runway Lighting above.

Threshold lights spacing

Threshold lights spacing is the distance between lights across the runway threshold. It is set by the standard the aerodrome follows, so no figures are given here. Correct spacing gives a clear green line that marks the start of the runway, and changes should be checked against the design drawings and the standard.

PLAN VIEW · FROM THE THRESHOLD THRESHOLD UP TO 900 M FROM THE THRESHOLD 30 or 60 m ONE BARRETTE, ENLARGED ≤ 1.5 m ≤ 1.5 m THREE OR MORE LIGHTS 3 TO 4.5 M LONG VARIABLE-INTENSITY WHITE WHAT TO CHECK 1 EXTENT up to 900 m from the threshold 2 PAIRS 30 m or 60 m apart along the runway 3 BARRETTE 3+ lights, 3 to 4.5 m long 4 SHORT RUNWAY under 1,800 m: stop at the midpoint SCHEMATIC · NOT TO SCALE · PAIR COUNT SHOWN IS NOT A DESIGN
Figure 17. Pairs of short white light bars either side of the centreline, starting at the threshold and running up to 900 m.AGL Visual Encyclopedia: What does the touchdown zone light pattern look like?
Interactive

Runway Lighting Engineering Checklist

A complete runway lighting project should be checked across four stages. Tick items off as you review a project — this resets on reload.

Design

Requirements & standards identified
Fixture layout completed
Circuit configuration established
CCR & transformer selection checked
0 / 4 complete

Installation

Fixture positions verified
Fixtures aligned
Transformers & connectors installed
Physical condition checked
0 / 4 complete

Testing

Insulation resistance & continuity
Transformer & CCR verification
Series-circuit current checked
Control & monitoring verified
0 / 4 complete

Photometry & Commissioning

Intensity & distribution checked
Colour & alignment verified
Operational & fault-monitoring test
Final documentation completed
0 / 4 complete
The Big Picture

The Complete Runway Lighting Engineering Chain

A runway lighting system is a coordinated engineering system combining visual guidance, electrical distribution, control, monitoring, mechanical installation and photometric performance. The objective is not simply to make runway lights illuminate — it is to ensure the installed system provides the intended visual guidance, electrical performance and operational reliability required for the aerodrome.

Design
Install
Test
Measure
Verify
Maintain
Test Yourself

Quick Knowledge Check

Q1. What is the runway light considered to be, within the overall system?

A. The only component that matters
B. An independent, standalone device
C. The final visible element of a larger electrical and control system
D. A purely mechanical fitting

Q2. Which lighting element identifies the beginning of the usable runway for a landing aircraft?

A. Runway edge lights
B. Runway threshold lights
C. Touchdown zone lights
D. Runway end lights

Q3. A fixture is correctly powered but incorrectly positioned. What does this mean?

A. The intended visual guidance can still be compromised
B. The system is fully compliant regardless of position
C. Photometry becomes unnecessary
D. The CCR setting is automatically corrected
Explore More

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DESIGN

AGL Design & Electrical Engineering

Return to the complete series circuit, CCR sizing and cable design knowledge base.

Open Design & Electrical Engineering →
PERFORMANCE

AGL Photometry

Verify the optical performance of the installed runway lighting system.

Open AGL Photometry →
DIAGNOSTICS

Troubleshooting Engine

Diagnose common runway lighting electrical and optical problems division by division.

Open the Troubleshooting Engine →
SYSTEMS

Taxiway Lighting Systems

Continuing the lit path from runway to apron.

Open Taxiway Lighting →
SYSTEMS

Approach Lighting Systems

Visual guidance leading into the runway environment.

Open Approach Lighting →
SAFEGUARD

Runway Guard Lights & Stop Bars

Incursion-prevention lighting at runway entry points.

Open Guard Lights & Stop Bars →
PROCESS

AGL Installation & Commissioning

Field installation and commissioning of runway lighting.

Open Installation & Commissioning →
CONTROL

ALCMS

The system that monitors and controls runway circuits.

Open ALCMS →
STANDARDS

ICAO Annex 14 AGL Requirements

The SARPs governing runway lighting configurations.

Open ICAO Annex 14 →

Design It Right. Light It Once.

From the runway layout to the final beam of light — explore the complete AGL design, photometry and troubleshooting knowledge base.

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QUICK FINDER

Runway centreline lights requirements and Related Topics

Looking for runway centreline lights requirements, or related topics? Use this finder to jump to the part of this runway lighting systems guide that covers each topic.

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runway centreline lights requirementsRunway Light Colours: Edge, Centreline, Threshold, End & Touchdown Zone
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FAQ

Frequently Asked Questions

Q1What is a runway lighting system?

It is the coordinated arrangement of visual lighting aids installed along and around a runway to give pilots the visual information needed for safe runway operations. Depending on runway type, operational category and standards, it may include edge, centreline, threshold, end and touchdown zone lights, approach lighting, lead-on and lead-off lighting, runway guard lights, stop bars, illuminated signs and PAPI.

Q2Why is runway lighting important?

The runway is the primary visual reference during approach, landing, takeoff and ground movement, especially in darkness or reduced visibility. Runway lighting lets pilots see where the runway is, where it begins and ends, where the centreline and edges are, where the touchdown area is and their position relative to the runway.

Q3What are the main runway lighting elements?

Edge lights define the lateral limits, centreline lights give longitudinal guidance, threshold lights identify the beginning of the usable runway, end lights identify the end, and touchdown zone lights add guidance in the touchdown area. Stop bars and illuminated signs support runway-protection and guidance around the runway.

Q4How does approach lighting relate to runway lighting?

Approach lighting provides visual guidance before the aircraft reaches the runway, creating a transition from the approach environment toward the threshold, and should be considered part of the overall runway visual guidance system. Elements include light bars, centreline and side elements, sequenced lighting and flashing elements.

Q5What do runway lighting colours mean?

Colour communicates function and location, for example at the edge, threshold, runway end, centreline, touchdown zone and approach systems. Exact colours, transition points and applicability depend on runway category and the applicable ICAO, FAA or project requirements.

Q6Does correct power guarantee correct runway guidance?

No. A fixture that is correctly powered but incorrectly positioned can still compromise the intended visual guidance, since position is a spatial system covering longitudinal spacing, transverse position, centreline location, threshold and runway end, touchdown zone and taxiway intersections.

Q7What electrical architecture do runway lights use?

Many runway lighting systems use series circuits, so multiple lights operate as part of a controlled constant-current circuit: CCR, series cable, isolation transformers and runway lights, with the return path to the CCR. The isolation transformers electrically separate each fixture from the primary series circuit.

Q8What does the CCR do in a runway lighting system?

It provides controlled current to the AGL series circuit and, depending on the system design, may provide multiple intensity levels. A problem anywhere in the chain, including CCR current, series-circuit performance, transformer operation or fixture output, can affect the final photometric performance.

Q9What determines which runway lights are installed?

The exact combination depends on the runway type, operational category, airport configuration and applicable standards.

Q10Is runway lighting just a collection of lights?

No. It is an integrated system of fixtures, series circuits, CCRs, isolation transformers, cables, connectors, control and monitoring, electrical infrastructure and photometric performance. The runway light is only the final visible element of a much larger electrical and control system.

Q11How does runway lighting work?

Runway lighting works as a series circuit: a constant current regulator (CCR) drives one current through a loop of cable, and each light is fed through an isolation transformer. The CCR sets the brightness step, the control system switches circuits and steps, and the colour and position of the lights give the pilot information about the runway.

Q12What color are runway edge lights?

Runway edge lights are white. On an instrument runway they turn yellow over the final portion of the runway to warn the pilot that the remaining runway is limited.

Q13What color are runway centerline lights?

Runway centerline lights are white for most of the runway, then alternate red and white, and finally become red over the last section before the runway end.

Q14What color are runway threshold lights?

Runway threshold lights are green when viewed from the approach direction. They mark the start of the usable landing runway, and runway end lights are red.

Q15What is runway light aiming?

Runway light aiming is setting the direction in which a runway light emits its beam, in both the horizontal and vertical planes, so that the main beam points where the pilot will see it. Aiming is checked with alignment tools and confirmed by measurement.

Q16How are runway lights installed?

Runway lights are installed on a light base set into the pavement or ground, with cables routed to the base and the fixture mounted on it. Inset lights sit flush in the pavement, while elevated lights use frangible couplings. Installation depth and orientation follow the manufacturer's drawings and the project specification.

Q17What is runway lighting NOTAM?

A runway lighting NOTAM is a notice to airmen announcing that part or all of the runway lighting is unserviceable, restricted or being worked on, so pilots know what lighting is available.

Q18What happens when runway lighting fails?

The effect depends on how much of the lighting is out. If the unserviceable lights exceed the aerodrome's serviceability limits, operations may be restricted, a NOTAM is issued, and night or low-visibility operations may be suspended until the lighting is restored. A standby supply and interleaved circuits reduce the chance of a total loss.

Field Insight

Engineering & Expert Notes

RS
By Rahul Sharma
Airfield Ground Lighting Specialist
Think of the Runway as a Set of Linked Systems
Overview

Edge, threshold, end, centreline and approach lights share circuits and controls. Faults can show up in more than one.

Understand the Series Circuit Layout
Electrical

Know which circuits feed which lights, and the effect of interleaving.

Test Every Intensity Step
Control

Check changes between steps and the interface with ALCMS.

Pay Attention to Inset Light Sealing
Installation

Water and heat damage are common in pavement fixtures.

Verify Photometry and Colour
Photometry

Measure where required rather than relying on appearance.

Keep Commissioning Data
Records

Baseline data supports future fault finding and audits.

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