Runway Lighting
Runway End Identifier Light (REIL) System
Rapid and positive identification of the runway approach end
REILs are two synchronized flashing lights on either side of the runway threshold, giving a conspicuous runway-end cue with project-specific optical, power, control and mounting configurations.
Supplied by Precision AGL Solutions
Product Overview
Runway End Identifier Light (REIL) System
What It Is
REILs provide a highly conspicuous visual indication of the approach end of a specific runway. The system is a pair of synchronized flashing lights located laterally on either side of the runway threshold.
The flashing cue helps pilots rapidly distinguish the intended runway from surrounding airport, roadway, industrial or other background lighting. It may use unidirectional lights facing the approach area or omnidirectional flashing lights.
Selected According To
- Runway identification and approach environment
- Ambient / background lighting and terrain contrast
- Unidirectional or omnidirectional requirement
- Intensity, synchronization, power and control
- Mounting, frangibility and environment
- Project technical specification
Always select from the approved airport lighting design and authority requirements.
Applications
Where REIL Systems Are Used
Rapid runway-end identificationPositive recognition of the intended runway.
Poor visual contrastRunways lacking contrast with surrounding terrain.
Heavy background lightingRunways surrounded by other lighting.
Reduced visibilityIdentification during reduced-visibility operations.
Night operationsFaster runway recognition than steady lights alone.
Upgrades & replacementRunway rehabilitation, legacy REIL replacement, new installations.
Function of REIL Lighting
Runway-End Identification
The System Supports
- Positive runway identification
- Rapid runway recognition
- Better visual contrast in complex environments
- Approach-path orientation
- Night and reduced-visibility identification
Supplementary Visual Aid
REILs are a supplementary visual aid and should be coordinated with the runway threshold, runway edge and approach lighting systems.
System Configuration
Left Flasher + Synchronization + Right Flasher
Left REILFlashing unit
SynchronizationTiming control
Right REILFlashing unit
Two units sit on opposite sides of the runway threshold and flash together. Final position and aiming must follow the approved installation drawing.
Synchronized Flashing
One Distinctive Identifier
Why It Matters
Both units must operate as a coordinated pair so the pilot perceives one distinctive runway-end identifier. Equipment should provide stable synchronization under normal operating and restart conditions.
Implemented Through
- Dedicated synchronizer
- Power / control unit
- Electronic or integrated flashing controller
- System-specific timing electronics
Unidirectional & Omnidirectional
Optical Arrangements
Unidirectional REIL
Aimed toward the approach area.
- Directional flashing output, approach-oriented beam
- Higher controlled intensity
- Defined horizontal and vertical beam
- Reduced unwanted output outside the approach sector
FAA JO 6850.2C specifies the aiming arrangement; units are normally located approximately symmetrically about the runway centreline.
Omnidirectional REIL
Flashing visibility over a substantially wider azimuth, for designs requiring wider-area runway-end identification.
FAA AC 150/5345-51B covers unidirectional and omnidirectional units in high-intensity, low-intensity and three-step versions. The configuration must follow the approved runway lighting requirement.
FAA Equipment Classification
AC 150/5345-51B Types and Styles
| FAA Type | Power Arrangement |
|---|---|
| L-849V | Airport-voltage power source |
| L-849I | Constant-current 6.6 A power supply |
| Style | Configuration |
|---|---|
| A | Unidirectional, high intensity, one step |
| B | Omnidirectional, high intensity, one step |
| C | Unidirectional, low intensity, one step |
| D | Omnidirectional, low intensity, one step |
| E | Unidirectional, three steps |
| F | Omnidirectional, three steps |
These classifications identify both the optical arrangement and the electrical supply concept.
Location, Symmetry & Aiming
Installation Geometry
Location
FAA places REILs laterally on both sides of the threshold. JO 6850.2C gives the optimum as approximately 40 ft from the runway edge, in line with the threshold lights, within permitted tolerances. On a runway equipped with a VASI the units move out to 75 ft from the runway edge.
- Other runways and taxiways
- Threshold and runway edge lights
- PAPI/VASI, terrain, structures
- Maintenance access
Symmetry
Units should be as nearly equidistant from the runway centreline as practicable, within a specified maximum lateral difference, keeping the identification visually centred on the approach.
Aiming
Typical FAA unidirectional arrangement:
- Approx. 10° vertical aiming
- Approx. 15° toe-out from a line parallel to the runway centreline
Adjust where standard geometry is unsatisfactory; the approved drawing and flight inspection govern.
Frangible Installation
Supports Near the Movement Area
FAA Installation Details
- Frangible couplings and grounding
- Concrete foundation
- Power / control wiring
- Controlled support height, breakaway near grade
FAA-Specific Dimensions
The FAA drawing identifies a maximum unit height of 36 in (91.4 cm) above grade and a frangible-coupling breaking point no more than 3 in (76.2 mm) above grade.
These are FAA installation-specific and should not be generalized to non-FAA projects.
Flash & Intensity
Flash Characteristics and Intensity Configuration
Specify
- Flash frequency and duration
- Pulse characteristics, repetition cycle
- Synchronization tolerance
- Restart behaviour and intensity
Values must come from the current approved equipment specification. REIL is synchronized flashing and should not be confused with a sequenced approach-flasher system.
Intensity Options
- Single high-intensity step
- Single low-intensity step
- Three intensity steps
Match to operating conditions, background lighting, visibility, approach system, control architecture and authority requirements.
Optical Performance
Balance Between the Two Units
Evaluate
- Effective flash intensity
- Horizontal and vertical beam coverage
- Main beam direction
- Synchronization and white output
- Visual conspicuity and glare control
Photometric Balance
- Equal or matched intensity
- Consistent colour and flash timing
- Beam alignment, lateral symmetry, vertical aiming
A single brighter or mis-aimed unit can make the pattern appear displaced from the runway centreline.
Electrical & Control
Power Architecture and Interfaces
Airport-Voltage Type (L-849V)
Airport AC Supply → REIL Power Supply / Controller → Left + Right Flashing Units
Synchronizer coordinates the pair.
Constant-Current Type (L-849I)
CCR → 6.6 A Circuit → REIL Power/Control Equipment → Left + Right Flashing Units
REIL cannot be assumed to use the same architecture as a conventional series-circuit fixture.
Control Interface May Include
- Airport lighting / AGL control system
- REIL power/control unit, maintenance panel
- Remote monitoring, operations system
- Radio control where applicable
Control Functions
- ON / OFF and intensity
- Fault monitoring
- Synchronization status
- Remote status, maintenance mode
LED vs Discharge-Type
Light-Source Technology
Discharge-Type
FAA AC 150/5345-51B is titled Specification for Discharge-Type Flashing Light Equipment and covers REIL and ODALS.
LED-Based Solutions
Where accepted by the authority and project specification:
- Fast switching, long life
- Reduced maintenance and energy use
- Consistent flash intensity
- Improved monitoring, repeatable synchronization
Environmental Performance
Outdoor Runway Environment
- Rain and water ingress
- Dust and humidity
- Temperature variation
- UV exposure
- Corrosion
- Wind
- Vibration
- Wildlife
- Electrical surges
- Mechanical impact
For elevated systems, focus on frangibility + foundation + support alignment + cable protection.
Installation Considerations
Verify Before Energizing
Location & Aiming
- Lateral distance and longitudinal position
- Threshold relationship, symmetry
- Clearance from other runways/taxiways
- Vertical angle, toe-out, beam axis
Support
- Foundation, frangible coupling
- Support height and breaking point
- Grounding, cable entry
Electrical
- Power supply, REIL controller
- Synchronizer
- Circuit identification
- Remote control, monitoring
Commissioning & Testing
Test as a Synchronized Pair
Visual & Electrical
- Units, lenses, supports, couplings, foundation
- Cabling, controller, synchronizer
- Supply voltage/current, continuity
- Insulation resistance, grounding, monitoring
Flash Synchronization
- Left and right flash together
- Stable repetition, no missing pulses
- No timing drift
- Correct restart after power interruption
Optical, Aiming & Photometric
- Vertical aiming and toe-out
- Beam direction, approach visibility
- Flash intensity, colour, distribution
- Unit-to-unit consistency
Inspection & Maintenance
Routine Inspection
Optical & Synchronization
- Lens cleanliness and damage
- Light output, flash intensity, alignment
- Both units flash together; no intermittent flashes
- Restart performance
Mechanical
- Support and foundation
- Frangible coupling
- Fasteners, corrosion
Electrical
- Power supply and controller
- Cable, connections, grounding
- Monitoring
Common Failure Modes
Typical Faults and Causes
| Symptom | Possible Causes |
|---|---|
| One REIL unit OFF | Light-source failure, power connection, cable fault, individual driver/controller problem |
| Both units OFF | Power-supply failure, control command, circuit interruption, controller failure, main protection fault |
| Units not synchronized | Synchronizer failure, timing-controller fault, communication/control fault, individual power-supply problem |
| Low flash intensity | Light-source degradation, optical contamination, driver or power-supply issue, wrong intensity setting |
| Incorrect beam direction | Support or foundation movement, incorrect aiming, installation error, mechanical damage |
| Unbalanced appearance | Different intensity or aiming, degradation, lens contamination, unit misalignment |
Engineering Troubleshooting
Troubleshooting Sequence
REIL controlCheck
Power supplyCheck
Synchronizer / controllerCheck
Left channelCheck
Right channelCheck
Light sourcesCheck
Optical alignmentVerify
Flash syncVerify
PhotometricsVerify
Identification problem: Runway contrast → background lighting → REIL location → aiming → intensity → threshold geometry
Product Selection Matrix
Key Selection Parameters
| Selection Parameter | Requirement |
|---|---|
| Application | Runway-end identification |
| Configuration | Paired synchronized flashers |
| Optical type | Unidirectional / omnidirectional |
| FAA type / style | L-849V / L-849I; A–F |
| Intensity | High / low / 3-step as applicable |
| Flash characteristic | Standard / project specific |
| Synchronization | Required |
| Location | Runway threshold area |
| Mounting / frangibility | Elevated, system-specific / applicable |
| Power | Airport voltage / 6.6 A constant current |
| Control and monitoring | Local / centralized; project specific |
| Documentation | TDS / photometry / certificates |
Product Selection Checklist
Before Ordering, Confirm
- Airport / project
- Runway designation
- Threshold location
- Approach direction
- REIL requirement
- Unidirectional / omnidirectional
- High / low / 3-step intensity
- FAA L-849V / L-849I
- Power source
- Synchronization
- Flash characteristic
- Optical aiming
- Beam distribution
- Runway-edge distance
- Longitudinal location
- Pair symmetry
- PAPI/VASI relationship
- Clearance from other runways/taxiways
- Mounting arrangement
- Frangible support
- Foundation
- Cable arrangement
- Control interface
- Monitoring
- Environmental requirements
- Applicable standard
- Manufacturer TDS
- Photometric documentation
- Synchronization documentation
- Type-test / compliance documents
- Project approval requirements
Technical Documents
Documents to Request
- Product datasheet
- REIL system specification
- FAA classification where applicable
- Photometric report
- Flash-intensity information
- Flash-rate specification
- Synchronization tolerance
- Pulse-duration information
- Unidirectional beam diagram
- Omnidirectional coverage diagram
- Intensity-step information
- Power-supply specification
- Controller specification
- Synchronizer specification
- Wiring diagram
- Control-interface documentation
- Monitoring/fault documentation
- Fixture dimensions
- Support dimensions
- Frangible-coupling details
- Foundation drawing
- Grounding requirements
- Cable-routing details
- Installation tolerances
- Environmental rating
- Installation manual
- Maintenance manual
- Compliance certificates
- Type-test reports
- Warranty information
Safety
Electrical Safety — Isolation and Lock-Out
WARNING — never open a live series circuit. An open series circuit driven by a constant-current regulator can produce dangerously high voltage. Opening, cutting or disconnecting any part of an energised circuit can cause serious injury or death and damage equipment.
- De-energise the circuit at the regulator and apply the site lock-out / tag-out (LOTO) procedure before any work
- Where the circuit must be isolated or shorted, use the series circuit cut-out switch or approved isolation device — not an improvised bypass
- Verify the circuit is de-energised and the output is isolated before touching conductors, connectors, splices, transformers or fixtures
- Do not disconnect or reconnect a fixture's secondary connector while the series circuit is energised: an open secondary on a series isolating transformer can develop hazardous voltage and damage the transformer
- Work on the movement area only under the airport's permit-to-work system, with the runway or taxiway closed as required, using qualified personnel and the manufacturer's instructions
- Follow the applicable national electrical safety regulations and site procedures
Standards & References
Verify the Applicable Edition
FAA
The FAA glossary defines REIL as two synchronized flashing lights, one on each side of the runway threshold, giving rapid and positive identification of a runway's approach end.
- AC 150/5345-51B — L-849V/L-849I, styles A–F
- JO 6850.2C — installation: location, symmetry, aiming
- AC 150/5340-30J — active visual-aid installation guidance
ICAO
ICAO calls these runway threshold identification lights (Annex 14, Vol. I, Chapter 5). They are a pair of white flashing lights, normally a flash rate of 60 to 120 per minute, located symmetrically about the runway centreline in line with the threshold and approximately 10 m outside each line of runway edge lights, and visible only in the approach direction. They are provided at the threshold of a non-precision approach runway where extra conspicuity is needed or other approach lighting cannot be provided, and where a threshold is displaced (permanently or temporarily) and extra conspicuity is needed. Confirm values and applicability against your edition and national implementation.
India
- DGCA requirements
- Airport-specific AGL specification
- Approved runway lighting layout and threshold location
- Approach category, PAPI/approach-light relationship
- Background-lighting conditions
- BOQ, Employer's requirements, Indian Standards
- Airport operator requirements
Always verify the applicable edition, approved equipment classification and project requirements before procurement, approval or installation.
Comparison
REIL vs Related Runway Lighting
| Feature | REIL | Threshold Light | Runway End Light | Sequenced Flasher System |
|---|---|---|---|---|
| Primary purpose | Rapid runway-end identification | Threshold identification | Physical runway-end indication | Approach-path lead-in |
| Operation | Flashing | Fixed | Fixed | Sequential flashing |
| Configuration | Pair of synchronized units | Threshold array | Runway-end array | Multiple stations |
| Typical colour | White flashing | Green | Red (runway end) | White flashing |
| Location | Threshold area | Threshold | Runway end | Extended approach centreline |
| Control | Synchronizer | Runway lighting circuit | Runway lighting circuit | Sequencer |
A runway may use REIL together with threshold and runway-end lights. Approach lighting gives transition and alignment; REIL gives positive identification of the runway end.
FAQ
REIL System — Frequently Asked Questions
What is a Runway End Identifier Light (REIL) system?
A REIL system is a pair of synchronized white flashing lights, one on each side of the runway threshold, that gives rapid and positive identification of the approach end of a runway. It is a supplementary visual aid and should be coordinated with the threshold, runway edge and approach lighting systems.
Where are REIL units located relative to the runway?
Two units are installed laterally, one on each side of the runway threshold. FAA JO 6850.2C gives the optimum position as approximately 40 ft from the runway edge, in line with the threshold lights, moving out to 75 ft on a runway equipped with a VASI. The units should be as nearly equidistant from the runway centreline as practicable. Final position and aiming must follow the approved installation drawing.
What is the difference between unidirectional and omnidirectional REIL?
Unidirectional REIL units are aimed toward the approach area and limit unwanted output outside the approach sector; the typical FAA arrangement is approximately 10° vertical aiming and 15° toe-out from a line parallel to the runway centreline. Omnidirectional units flash over a substantially wider azimuth for designs that need wider-area runway-end identification. The choice must follow the approved runway lighting requirement.
What do FAA L-849V and L-849I mean for REIL equipment?
Under FAA AC 150/5345-51B, L-849V equipment is powered from an airport-voltage source and L-849I equipment from a constant-current 6.6 A power supply. Styles A to F define the optical arrangement and intensity: A unidirectional high intensity, B omnidirectional high intensity, C unidirectional low intensity, D omnidirectional low intensity, E unidirectional three-step and F omnidirectional three-step.
How does ICAO describe REIL?
ICAO Annex 14, Volume I calls them runway threshold identification lights. They are a pair of white flashing lights, normally with a flash rate of 60 to 120 per minute, located symmetrically about the runway centreline in line with the threshold and approximately 10 m outside each line of runway edge lights, visible only in the approach direction. Confirm values and applicability against your edition and national implementation.
When is a REIL system needed?
REILs are used where rapid runway-end identification is valuable: runways with poor visual contrast against surrounding terrain, runways surrounded by heavy background lighting, night and reduced-visibility operations, and runway rehabilitation or replacement of legacy REIL installations. Whether a REIL is required is decided by the approved airport lighting design and the authority's requirements.
How is REIL different from a sequenced flashing light system?
A REIL is a synchronized pair of flashers at the runway threshold that identifies the runway end. A sequenced flashing light system uses multiple stations flashing in sequence along the extended approach centreline to give approach-path lead-in. They serve different functions and can be used on the same runway together with threshold and runway-end lights.
Do REIL units need frangible mounting?
Elevated REIL units near the movement area are installed on frangible supports with a controlled support height and a breakaway point near grade. The FAA drawing identifies a maximum unit height of 36 in (91.4 cm) above grade and a frangible-coupling breaking point no more than 3 in (76.2 mm) above grade. These dimensions are FAA installation-specific and should not be generalized to non-FAA projects.
Can LED REIL replace discharge-type REIL?
FAA AC 150/5345-51B is titled Specification for Discharge-Type Flashing Light Equipment and covers REIL and ODALS. LED-based REIL solutions offer fast switching, long life, reduced maintenance and energy use, and repeatable synchronization, and can be used where accepted by the authority and the project specification.
What are the common REIL faults and how are they troubleshot?
Common symptoms are one unit off, both units off, units not synchronized, low flash intensity, incorrect beam direction and an unbalanced appearance. Troubleshoot in sequence: REIL control, power supply, synchronizer or controller, left and right channels, then light sources, followed by verification of optical alignment, flash synchronization and photometrics. See the electrical safety warning before working on any circuit.
What should be confirmed and requested before ordering a REIL system?
Confirm the runway designation, threshold location, approach direction, optical type, intensity requirement, FAA type and style, power source, synchronization, aiming, mounting and frangible support, and control interface. Request the product datasheet, photometric report, flash-rate and synchronization documentation, power and controller specifications, wiring and foundation drawings, compliance certificates and type-test reports.
Why Precision AGL Solutions
A Complete-System Approach
We treat REIL as a dedicated runway-identification safety visual aid:
Runway → Threshold → REIL Location → Optical Type → Flashing Units → Synchronization → Power → Control → Aiming → Photometry → Maintenance
This helps ensure both REIL units operate as one coordinated visual system.
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 REIL System Selection
Planning a runway-end identification upgrade, runway rehabilitation or new airport lighting installation? Submit your runway designation, threshold location, runway width, approach direction, existing runway lighting, background-lighting conditions, visibility, optical, intensity and power requirements, control system, BOQ, technical specification and existing REIL documentation. We can review the runway environment and support selection of the REIL configuration, flashing equipment, power/control arrangement, mounting system and documentation.
- Emailprecisionaglsolutions@gmail.com
- Websiterahulsharmaagl.in
- LinkedInPrecision AGL Solutions
- Phone+91 98214 96412
Engineering Note
REILs should not be marketed simply as “flashing runway lights.” Their defining characteristics are the paired configuration, synchronization, runway-end identification function, optical directionality, flash intensity, aiming and dedicated control/power arrangement.
For FAA projects the equipment specification is AC 150/5345-51B and installation criteria are in JO 6850.2C. Always select from the approved runway lighting design, authority requirements, current manufacturer data and project power/control architecture.
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.