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Definitions are simplified — they are not normative text. Where a glossary entry differs from the definition in ICAO Annex 14, an FAA advisory circular, an IEC/BIS standard or your project specification, the official document prevails. Safety-critical work must follow your aerodrome’s approved procedures. Read the full disclaimer ↓
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AGL Glossary

Search 1,033 terms, abbreviations, components, and technical definitions used across Airfield Ground Lighting engineering, standards, and field operations.

1,033Terms
27Letter Groups
10Categories

1,033 terms in the glossary

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6.6 A Series Circuit

Airport lighting series circuit designed around a nominal regulated operating current of 6.6 A, with individual loads connected through series isolation transformers.

Electrical

20 A Series Circuit

Airport lighting series circuit designed around a nominal regulated operating current of 20 A where the equipment and project architecture use this configuration.

Electrical

A

A-SMGCSAdvanced Surface Movement Guidance and Control System

Advanced Surface Movement Guidance and Control System (A-SMGCS) is an integrated system of surveillance, identification, routing, guidance and related functions used to support the safe and efficient movement of aircraft and vehicles on the aerodrome surface.

Systems

A-SMGCS Alarm

System-generated alert indicating a fault, conflict, unavailable function or abnormal condition requiring attention.

Systems

A-SMGCS Data Link

Communication path used to exchange operational or system data between A-SMGCS components.

Systems

A-SMGCS Level 1

Basic surface movement guidance and control capability centred on surveillance/identification functions and the operational information needed for safe surface movement.

Systems

A-SMGCS Level 2

Enhanced surface movement capability adding routing or guidance-related functions to improve controlled movement beyond basic surveillance/identification.

Systems

A-SMGCS Level 3

Advanced surface movement capability that integrates guidance and/or conflict-management functions with the underlying surveillance and routing architecture.

Systems

A-SMGCS Level 4

Advanced A-SMGCS capability incorporating the applicable integrated surveillance, routing, guidance and conflict-management functions defined by the adopted system concept.

Systems

A-SMGCS Lighting Interface

Interface through which A-SMGCS exchanges movement-guidance information with airfield lighting equipment or its control system.

Systems

A-SMGCS Network Interface

Physical or logical network interface connecting an A-SMGCS subsystem to another system or data network.

Systems

AAIAirports Authority of India

Airports Authority of India — the statutory body responsible for managing, operating and developing civil aviation infrastructure at Indian airports, including approval and oversight of airside AGL design and safety.

Standards

Acceptance Criteria

The specific, measurable requirements a product, test result or piece of work must satisfy to be accepted as compliant.

Testing

Acceptance Limit

The minimum or maximum photometric, electrical or dimensional value a measured result must fall within for a fixture, circuit or system to be accepted or pass a test.

Testing

Acceptance Test

A formal test or set of tests used to determine whether equipment or an installed system satisfies the defined acceptance criteria before handover or use.

Testing

ADS-B Surface Surveillance

Use of Automatic Dependent Surveillance-Broadcast data to support identification and tracking of equipped surface targets.

Systems

Aerodrome Beacon

An aeronautical beacon installed at an aerodrome to provide a visual identification cue from the air.

Fixtures

Aerodrome Elevation

The elevation above mean sea level of the highest point of the landing area, published as a reference datum for aerodrome operations.

Operations

Aerodrome Manual

The primary regulatory document, submitted to the civil aviation authority, describing an aerodrome's facilities, procedures and operating conditions, including its AGL system.

Standards

Aerodrome Operator

The organisation legally responsible for the safe operation, maintenance and regulatory compliance of an aerodrome, including its AGL systems.

Standards

Aerodrome Visual Aid

Any visual device, lighting, marking or sign, provided at an aerodrome to assist pilots and vehicle drivers during approach, landing, takeoff and ground movement.

Operations

Aeronautical Information

Information concerning aerodrome facilities, procedures and hazards, published through official channels such as the AIP or NOTAM, to support flight planning and operations.

Documentation

AGLAirfield Ground Lighting

Integrated visual guidance system using lights, illuminated signs, power, control and monitoring equipment to support aircraft movement on the aerodrome.

Systems

AGL Acceptance Test Record

Formal record demonstrating whether equipment or an installed AGL system met defined acceptance requirements.

Testing

AGL Alarm Test

A test that deliberately triggers each monitored fault condition to confirm the ALCMS or CCR correctly detects, displays and logs the alarm.

Testing

AGL Alignment Deviation

Difference between the installed optical/mechanical orientation and the approved aiming or alignment reference.

Testing

AGL Alignment Verification

A check confirming that a fixture's physical aiming angle matches its design value, performed using an inclinometer or aiming template.

Testing

AGL Apron Crossing

Protected cable/duct route crossing an apron area while maintaining pavement integrity and cable protection.

Electrical

AGL Automatic Transfer Switch

Switching device that automatically transfers a connected load between designated power sources according to defined source-health and transfer logic.

Electrical

AGL Base Can Level

Elevation and levelness of the base-can mounting interface relative to the specified pavement or datum.

Fixtures

AGL Bonding Conductor

Conductor used to establish electrical bonding between metallic parts so they remain at substantially the same potential and provide a fault-current path where required.

Electrical

AGL Breakdown Maintenance

Unplanned maintenance carried out in response to an AGL failure that has already occurred, as distinct from maintenance performed on a scheduled or condition-based basis.

Maintenance

AGL Burn-In Test

Extended operation intended to expose early-life failures or unstable behavior before equipment is released for service.

Testing

AGL Cable Protection Slab

Protective slab installed above an underground cable/duct route to reduce risk of mechanical damage from excavation or loading.

Electrical

AGL Cable Pulling Record

Controlled record of cable identification, route, pulling conditions and installation observations during cable installation.

Documentation

AGL Cable Slack

Controlled additional cable length left at a termination or fixture to permit installation, maintenance and reconnection without excessive mechanical stress.

Maintenance

AGL Cable Termination Point

Defined location where a cable is electrically and mechanically connected to equipment, a connector, transformer or joint.

Electrical

AGL Calibration Certificate Review

Review confirming that a test instrument has valid calibration and suitable traceability before measurement.

Testing

AGL Changeover Panel

Electrical panel containing switching/control equipment used to transfer or select the supply feeding designated AGL loads.

Electrical

AGL Circuit Isolation Point

Defined switch, breaker, connector or other point used to electrically isolate a circuit for safe work.

Electrical

AGL Circuit Load Test

A test in which a series circuit is energised and its actual load, voltage, current and resistance, is measured and compared against the calculated design load.

Testing

AGL Circuit Open Fault

Loss of electrical continuity in a series circuit caused by a broken conductor, connector, transformer lead, fixture or termination.

Electrical

AGL Circuit Short Fault

Unintended low-impedance connection between conductors or to earth that changes the designed circuit current path.

Electrical

AGL Commissioning Checklist

Structured checklist covering functional, electrical, control and operational checks required before AGL system acceptance.

Testing

AGL Communication Test

A test verifying that data communication between the ALCMS, CCRs and field devices is functioning correctly, including message integrity and response time.

Testing

AGL Concrete Encased Duct

Duct installation surrounded by concrete to provide mechanical protection and maintain a controlled cable pathway.

Electrical

AGL Conditional Acceptance

Acceptance granted with defined outstanding conditions, restrictions or corrective actions that must be tracked to closure.

Testing

AGL Connector High Resistance

Abnormally high contact or termination resistance causing voltage drop, heating or unstable operation.

Electrical

AGL Connector Moisture Failure

Connector malfunction or insulation degradation caused by water/moisture ingress, inadequate sealing or environmental damage.

Electrical

AGL Crossing Detail

Drawing or installation detail showing how an AGL cable/duct crosses another route, pavement or service.

Documentation

AGL Current Balance Check

Measurement comparing the currents across a series circuit's fixture branches or feeders to identify abnormal loading, a poor connection or a developing imbalance.

Testing

AGL Current Measurement

The recording of actual current flowing in a series circuit, taken to verify it matches the CCR's set output and the calculated circuit load.

Testing

AGL De-Energized Circuit Test

Test performed with the circuit safely isolated and verified dead, typically for continuity, insulation or wiring checks.

Testing

AGL Dead Circuit Verification

Verification that an isolated circuit is not energized before personnel perform testing or maintenance.

Testing

AGL Defect Register

A tracked log of identified AGL defects recording location, description, priority, assigned action and close-out status.

Maintenance

AGL Dielectric Withstand Acceptance

Acceptance evaluation of insulation performance under the specified dielectric test voltage, duration and leakage criterion.

Testing

AGL Distribution Panel

The panel from which incoming power is distributed to individual CCRs or AGL sub-circuits, typically including circuit breakers for each outgoing feed.

Electrical

AGL Duct Bank

Group of ducts installed together to carry multiple cables with controlled routing and separation.

Electrical

AGL Duct Cleaning

Removal of debris, water and obstructions from an installed duct before cable installation.

Electrical

AGL Duct Installation

Installation of underground ducts or conduits that provide a defined protected path for AGL cables.

Electrical

AGL Duct Mandrel Test

Test in which a calibrated mandrel is pulled through a duct to verify clear internal passage and usable bore.

Testing

AGL Earth Continuity

Electrical continuity of the protective/bonding path between equipment and the designated earthing system.

Electrical

AGL Earth Continuity Test

Test verifying a low-resistance continuous protective-earth path between accessible metallic parts and the designated earthing point.

Testing

AGL Earth Grid Resistance

Overall resistance of an interconnected earthing grid to the remote earth reference.

Electrical

AGL Electrical Handover

Formal transfer of an electrical system from construction/testing responsibility to the operating or maintenance organization with required records and status information.

Testing

AGL Electrical Isolation

The de-energising and physical disconnection of an AGL circuit or component, confirmed dead, before personnel carry out work on it.

Electrical

AGL Electrical Lockout

Application of a lock or controlled isolation device to prevent inadvertent energization during electrical work. See also: Lockout Tagout.

Maintenance

AGL Emergency Shutdown

A control function that immediately de-energises AGL circuits in response to a hazardous condition, operable locally or remotely.

Electrical

AGL Emergency Supply

Source provided to maintain designated emergency loads under defined abnormal or loss-of-normal-supply conditions.

Electrical

AGL Endurance Test

Test that operates equipment for a defined duration or duty cycle to verify sustained performance.

Testing

AGL Energization Checklist

Controlled checklist used during initial energization to verify safe switching, expected current, alarms, control response and abnormal conditions.

Documentation

AGL Energized Circuit Test

Test performed with the AGL circuit energized to verify current, control, monitoring or functional behavior under live operating conditions.

Testing

AGL Essential Distribution Board

Distribution board dedicated to essential loads and supplied from the designated essential power arrangement.

Electrical

AGL Essential Supply

Electrical source classified as essential for maintaining defined airport/AGL functions when the normal source is unavailable.

Electrical

AGL Excessive Circuit Load

Connected load that causes the series circuit/CCR to operate outside its intended loading range.

Electrical

AGL Failure Analysis

Technical examination of a failed AGL component or system to determine failure mechanism, contributing conditions and corrective action.

Maintenance

AGL Fault Simulation

The deliberate introduction of a fault condition on a test bench or de-energised circuit to verify protective devices, alarms or monitoring systems respond correctly.

Testing

AGL Fault Symptom

Observable indication of abnormal AGL behavior that guides diagnostic testing but does not by itself identify the root cause.

Testing

AGL Fault Tree

Logical decomposition of an AGL failure into possible causes and branching checks used to identify the root cause.

Maintenance

AGL Feeder Cable

Power cable carrying electrical supply from a distribution source to an AGL load or equipment such as a CCR.

Electrical

AGL Feeder Isolation

Controlled disconnection of an AGL feeder from its supply for maintenance, testing or fault isolation.

Testing

AGL Feeder Panel

Panel containing protective and switching devices for outgoing AGL electrical feeders.

Electrical

AGL Feeder Protection

Protective devices and settings applied to an AGL feeder to clear faults while protecting conductors and equipment.

Electrical

AGL Final Acceptance

Formal confirmation that the completed AGL work meets the approved scope and acceptance requirements.

Testing

AGL Fixture Flicker Fault

Unstable or visibly fluctuating fixture output caused by driver, power, connection, control or thermal problems.

Fixtures

AGL Fixture Intermittent Fault

Fixture failure that appears and disappears with changes in temperature, vibration, moisture ingress, current level or connection looseness, making it harder to reproduce during fault-finding.

Fixtures

AGL Fixture Low-Intensity Fault

Condition in which a fixture operates but produces less light than the applicable photometric or functional requirement.

Fixtures

AGL Fixture No-Light Fault

Condition in which an AGL fixture produces no intended light output despite a commanded operating state.

Fixtures

AGL Fixture Overheating

Fixture temperature exceeding its intended thermal operating condition, potentially reducing optical output or component life.

Fixtures

AGL Fixture Water Ingress Fault

Entry of water into an AGL fixture or enclosure that can degrade optics, electronics, insulation or mechanical components.

Fixtures

AGL Fixture Wrong-Color Fault

Fixture output whose chromaticity or commanded color does not match the intended AGL function.

Fixtures

AGL Functional Performance Test

Test that verifies an AGL function performs its intended sequence, response and output under defined conditions.

Testing

AGL Generator Supply

Electrical supply produced by an engine-generator set and used as an alternate or emergency source for designated AGL loads.

Electrical

AGL Grounding Grid

A network of interconnected buried conductors forming the earthing system for an AGL substation or CCR building, providing a low-impedance path to ground.

Electrical

AGL High Leakage Fault

Condition in which leakage current to earth or between conductors exceeds the expected level for the circuit and insulation system.

Electrical

AGL Inspection and Test Plan

Controlled project document defining inspections, tests, acceptance criteria, responsibilities and hold/witness points for the AGL work.

Testing

AGL Inspection Request

Formal request submitted for inspection or testing of a defined installation activity or completed work package.

Testing

AGL Installation Drawing

Drawing that locates fixtures, bases, cables, equipment and installation details against the approved airport layout.

Documentation

AGL Interlock Test

A test confirming that safety or logic interlocks, such as stop bar and centreline interlocking, correctly prevent an unsafe combination of lighting states.

Testing

AGL Isolation Procedure

The documented sequence for safely disconnecting and locking out an AGL circuit or item of equipment from its electrical supply before maintenance work begins.

Maintenance

AGL ITP Witness Point

Inspection stage where the designated party is notified and may witness the activity without necessarily stopping subsequent work.

Testing

AGL Junction Box

An enclosure where cables are joined, branched or terminated, providing mechanical protection and access for testing or maintenance.

Electrical

AGL Latent Fault

Existing defect that is not immediately apparent during normal operation but can prevent a required function when demanded.

Maintenance

AGL Low Insulation Fault

Condition indicated by insulation resistance below the applicable acceptance or operating criterion.

Testing

AGL Maintenance Record

The formal documentation retained as evidence that scheduled or corrective AGL maintenance was carried out, and its outcome.

Maintenance

AGL Material Inspection

Inspection confirming that delivered AGL materials match approved type, quantity, identification, condition and documentation.

Maintenance

AGL Monitoring in LVP

Continuous or periodic monitoring of critical AGL functions needed to maintain the approved low-visibility operating configuration.

Systems

AGL Mounting Surface

Physical surface that supports the AGL fixture and establishes its seating, elevation and orientation.

Fixtures

AGL Nonconformance Record

Controlled record describing a deviation from an approved requirement and its disposition.

Documentation

AGL Nuisance Trip

Protective trip or shutdown occurring without the intended fault condition, often requiring investigation of thresholds, leakage, transients or equipment behavior.

Electrical

AGL Overcurrent Protection

Devices such as fuses or circuit breakers that automatically disconnect a circuit when current exceeds a safe level, preventing damage or fire.

Electrical

AGL Pavement Crossing

Construction detail used to route an AGL cable/duct across paved aircraft or vehicle movement surfaces.

Electrical

AGL Permanent Fault

Fault that remains present until the failed component, connection or condition is corrected.

Maintenance

AGL Phase Identification Test

Test used to confirm correct identification of conductors/phases in an upstream electrical supply or panel.

Testing

AGL Photometric Acceptance Test

A field measurement of an installed fixture's or circuit's luminous intensity, taken after commissioning and compared against the design acceptance criteria to confirm the installed system meets its specified light output.

Photometry

AGL Photometric Nonuniformity

Undesired spatial variation in measured light output relative to the required distribution or uniformity criterion.

Photometry

AGL Photometric Underperformance

Measured optical performance below the applicable intensity, luminance, uniformity or other photometric acceptance criterion.

Photometry

AGL Planned Maintenance

Maintenance scheduled in advance at fixed time or usage intervals, rather than triggered by a fault.

Maintenance

AGL Power Factor Test

A test measuring the ratio of real to apparent power drawn by an AGL load, used to assess transformer or CCR loading characteristics.

Testing

AGL Pre-Commissioning Inspection

A physical inspection carried out before commissioning tests begin, confirming installation is complete and correct before the system is energised.

Testing

AGL Pre-Energization Checklist

Checklist confirming that an AGL circuit/equipment is ready to be energized after safety, wiring, insulation and configuration checks.

Documentation

AGL Prospective Fault Current

Current that would flow at a specified point if a fault of negligible impedance occurred under the assumed system conditions.

Electrical

AGL Protection Coordination

Selection and setting of protective devices so their operating characteristics provide the required protection and coordination.

Electrical

AGL Protective Earth Test

Test verifying continuity and integrity of the protective-earth connection for equipment requiring protective bonding.

Testing

AGL Proving Dead

Verification using an approved test instrument that an isolated electrical circuit is not energized before work begins.

Testing

AGL Provisional Acceptance

Temporary acceptance allowing controlled use before all final acceptance conditions are closed.

Testing

AGL Punch List

A list of outstanding defects or incomplete items identified during inspection, to be closed out before final acceptance of the works.

Testing

AGL Re-Energization Procedure

Controlled sequence for removing isolation controls and restoring an electrical circuit to service after work and safety checks are complete.

Documentation

AGL Remote Control Test

A test confirming that commands issued from the ALCMS or tower control panel correctly operate the intended AGL circuit or fixture.

Testing

AGL Repetitive Fault

Fault that recurs after reset or correction and therefore indicates an unresolved underlying cause.

Maintenance

AGL Road Crossing

Protected cable/duct crossing beneath or through a road used by airport vehicles or aircraft-support traffic.

Electrical

AGL Safe Isolation

Controlled process of disconnecting, securing, proving dead and preventing re-energization of an electrical circuit before work.

Electrical

AGL Safety Interlock

A control mechanism that prevents a hazardous action, such as re-energising a circuit, until a specified safety condition is satisfied.

Electrical

AGL Spare Cable Length

Reserved cable length retained for future termination, maintenance or repositioning of connected equipment.

Maintenance

AGL SPD Coordination

The design process of selecting and locating surge protective devices at different points in an AGL system so they operate together to limit surge energy reaching sensitive equipment. See also: AGL Surge Coordination.

Electrical

AGL SPD Status Indicator

Visual or remote indication showing the service condition or failure state of a surge protective device.

Electrical

AGL SPD Type

Classification of a surge protective device according to its intended installation/application and applicable standard.

Standards

AGL Standby Supply

Alternate electrical source intended to supply designated loads when the normal source fails or is unavailable.

Electrical

AGL Surge Coordination

Selecting and coordinating surge protective devices at the CCR, transformers and field equipment so each stage clamps transient voltage before it reaches downstream equipment with a lower insulation withstand rating. See also: AGL SPD Coordination.

Electrical

AGL System Performance Test

Integrated test verifying that multiple AGL subsystems operate together as specified.

Testing

AGL Terminal Block

A modular block of connection points used to terminate and join conductors within a panel, junction box or CCR enclosure.

Electrical

AGL Test Record

Controlled record that documents the conditions, instruments, measured results, acceptance outcome and observations from an AGL test. It provides traceable evidence that a defined inspection or test was performed and records its disposition.

Testing

AGL Transformer Insulation Failure

Degradation or breakdown of transformer insulation causing unacceptable leakage or dielectric performance.

Electrical

AGL Trench Backfill

Approved material placed around and above an installed cable/duct to provide protection and restore the excavation.

Electrical

AGL Troubleshooting Test Point

Defined electrical or control measurement location used to isolate a fault without unnecessarily disturbing the circuit.

Testing

AGL Troubleshooting Workflow

Structured sequence for isolating an AGL fault from symptom identification through measurement, fault localization, correction and verification.

Testing

AGL Underloaded Series Circuit

Series circuit whose connected load is insufficient for the intended CCR operating range or design condition.

Electrical

AGL UPS Supply

Uninterruptible power source that maintains designated control, monitoring or other critical loads through a transfer or short interruption in the normal supply.

Electrical

Aiming Angle

The vertical and horizontal angle at which a light fixture's optical axis is set relative to a reference plane, determined during installation or alignment to direct the beam to its design position.

Fixtures

Aircraft Movement Area

The part of an aerodrome used for aircraft takeoff, landing and taxiing, comprising the manoeuvring area and the apron(s). See also: Movement Area.

Operations

Aircraft Parking Position

A designated area on an apron where an aircraft is parked for loading, unloading, servicing or overnight stay.

Operations

Aircraft Stand

A designated area on an apron intended for parking or servicing an aircraft.

Operations

Aircraft Stand Guidance System

A system that provides visual guidance to an aircraft during movement into or within an aircraft stand.

Operations

Aircraft Tracking

Continuous or periodic determination of an aircraft's identity and movement position on the aerodrome surface.

Operations

Airfield CableAirfield Lighting Cable

Cable specifically rated and constructed for burial or duct installation in the airside environment, meeting the mechanical and electrical requirements of AGL circuits.

Electrical

Airfield Lighting Isolation

The controlled de-energising of an airfield lighting circuit for maintenance, confirmed and communicated before work begins.

Maintenance

Airfield Sign

Illuminated or retroreflective aerodrome sign used to provide standardized visual information, direction, location, destination or mandatory instruction on the movement area.

Signage

Airfield Work Zone

A designated and marked area on the airside where maintenance or construction work is being carried out, requiring specific access, barricading and notification controls.

Maintenance

Airside Driving

Driving of vehicles within the airside area, governed by an aerodrome's specific rules, permits and training requirements distinct from public road driving.

Operations

Airside Electrical Safety

The set of practices and controls, such as isolation, PPE and permits, applied specifically to electrical work carried out in the airside environment.

Documentation

Airside Safety

The overall set of practices, rules and controls in place to protect personnel, vehicles and aircraft operating within the airside environment.

Operations

Airside Works

Any construction, maintenance or installation activity carried out within the airside area, subject to specific access, safety and notification controls.

Operations

ALCMSAirport Lighting Control and Monitoring System

Airport Lighting Control and Monitoring System that provides centralized control, status indication, alarms and monitoring of airport lighting facilities.

Systems

ALCMS Access Control

Controls which users or user roles may access ALCMS functions, displays, commands and configuration areas. Access control typically combines authentication with role-based permissions so operational actions and configuration changes are limited to authorised personnel.

Systems

ALCMS Alarm Management

Organises, prioritises and records alarms generated by the ALCMS, including fault, warning and acknowledgement states. It provides operators with a consistent method for recognising, reviewing and closing lighting-system alarms.

Systems

ALCMS Architecture

Defines the arrangement of ALCMS servers, workstations, controllers, networks, field interfaces and communication paths. The architecture establishes how control, monitoring, redundancy and data exchange functions are distributed across the system.

Systems

ALCMS Backup

Provides recovery capability for ALCMS configuration, application data or historical records after equipment failure or data loss. The backup arrangement defines what information is copied, where it is stored and how restoration is performed.

Systems

ALCMS Circuit Monitoring

Collects and presents operating status or fault information from AGL circuits and associated control equipment. Circuit monitoring allows the ALCMS to identify abnormal states and provide corresponding indications or alarms.

Systems

ALCMS Command

Command issued by an operator or supervisory function to change the state or operating level of a controlled AGL function. An ALCMS command is transmitted to the relevant control interface and requires an associated field response.

Systems

ALCMS Command Verification

Confirms that an ALCMS command produced the intended field response and corresponding status indication. Verification may compare the commanded state with feedback from the CCR, circuit-control equipment or monitored field device.

Systems

ALCMS Communication Failure

Indicates loss or degradation of communication between ALCMS components or between the ALCMS and connected field equipment. The failure can prevent command transfer, status updates or alarm reporting until the communication path is restored.

Systems

ALCMS Cybersecurity

Protective measures applied to the ALCMS to preserve authorised access, system availability and integrity of control data. Cybersecurity controls can include authentication, access restrictions, network segmentation, logging and controlled software changes.

Systems

ALCMS Data Logging

Records selected ALCMS events, commands, alarms and status changes with associated time information. Data logging provides an operational history that can support troubleshooting, incident review and verification of system behaviour.

Systems

ALCMS Database

Structured data store used by the ALCMS to retain configuration, equipment information, user data, events or other application records. The database supplies stored information to the system functions that require persistent data.

Systems

ALCMS Emergency Control

ALCMS function that provides operator or supervisory control of designated lighting during an emergency condition. It is intended to execute defined emergency actions while providing status feedback and alarm indication.

Systems

ALCMS Ethernet

Ethernet communication technology used to connect ALCMS components over a local or routed data network. It carries control, monitoring and application traffic between compatible servers, workstations, controllers and network devices.

Systems

ALCMS Event Log

Chronological record of significant ALCMS events such as commands, alarms, operator actions and system changes. The event log supports traceability by preserving the sequence and time of recorded system activities. See also: Event Log.

Systems

ALCMS Fail-Safe State

Defined ALCMS operating condition entered when a detected failure prevents normal control or monitoring. The fail-safe state applies predetermined outputs or restrictions intended to prevent an unsafe or uncontrolled lighting condition.

Systems

ALCMS Fiber Link

Optical-fiber communication path connecting ALCMS equipment, network devices or remote control interfaces. The fiber link carries digital control and monitoring data while providing electrical isolation between connected network points.

Systems

ALCMS Graphic Display

Graphical operator display that presents ALCMS equipment status, circuit states, alarms and available controls in a visual screen layout. It helps operators identify the affected lighting function and issue permitted commands.

Systems

ALCMS Lamp Monitoring

Monitors the operating condition of lamps or lighting circuits and reports detected failures or abnormal states to the ALCMS. The monitoring method depends on the field equipment and may use electrical, optical or status-feedback information.

Systems

ALCMS LVP Control

ALCMS functions used to select, monitor and alarm the lighting configurations required for low-visibility operations.

Systems

ALCMS Modbus

Modbus communication protocol used to exchange control, status or measurement data between compatible ALCMS equipment and connected devices. The implementation may use a serial or Ethernet-based Modbus variant defined by the system design.

Systems

ALCMS Network

Data network interconnecting ALCMS servers, workstations, controllers and communication interfaces. The network provides the communication paths required for supervisory control, monitoring, alarms and system data exchange.

Systems

ALCMS Operator Interface

Operator-facing interface through which authorised personnel view ALCMS status, alarms and controls and issue permitted lighting commands. It provides the human-machine interaction layer between the operator and the control application.

Systems

ALCMS PLC

Programmable logic controller used within an ALCMS to execute defined control, interlocking, monitoring or interface logic. The PLC exchanges signals with field equipment and higher-level supervisory functions according to the configured application.

Systems

ALCMS Protocol

Defined communication rules and message structure used by ALCMS components to exchange commands, status, alarms or data. The protocol determines how connected devices interpret transmitted information and respond to valid messages.

Systems

ALCMS Redundancy

Provision of alternative ALCMS components, communication paths or power arrangements so a single defined failure does not remove the required control or monitoring function. The redundancy arrangement depends on the system architecture and availability requirements.

Systems

ALCMS Remote I/O

Remote input/output interface that exchanges field signals with an ALCMS controller over a communication network. Remote I/O reduces the need to route every field signal directly to the central control panel or PLC.

Systems

ALCMS Server

Computer system that hosts ALCMS applications, databases or services required for supervisory control and monitoring. The server provides shared processing or data functions to connected operator workstations and system clients.

Systems

ALCMS Status Monitoring

Continuous or periodic presentation of ALCMS equipment and circuit status to identify normal, abnormal or unavailable conditions. Status monitoring supplies operators and supervisory functions with the information needed for operational control.

Systems

ALCMS User Authentication

Process that verifies the identity of an ALCMS user before permitting access to protected functions. User authentication can use credentials or another approved identity mechanism defined by the system security design.

Systems

ALCMS Workstation

Computer terminal used by an operator to access ALCMS applications, displays, alarms and authorised control functions. A workstation provides the local human-machine interface to the supervisory lighting-control system.

Systems

ALCMS-A-SMGCS Interface

Data/control interface exchanging lighting commands, status or alarms between the ALCMS and an A-SMGCS environment.

Systems

Alignment Check

A measurement or verification that the installed equipment orientation or position agrees with the approved reference geometry.

Testing

ALSApproach Lighting System

Approach Lighting System providing a visual reference during the approach and transition toward the runway threshold.

Fixtures

APAPIAbbreviated Precision Approach Path Indicator

Abbreviated Precision Approach Path Indicator (APAPI) system using two optical light units to provide visual approach-slope guidance. The optical units produce the required white/red visual indications used to determine whether the aircraft is above, on or below the intended approach path.

Fixtures

APAPI Photometric Verification

Field verification of APAPI optical performance against the approved alignment and photometric requirements. The verification uses measured or observed light output to confirm that the installed two-unit system provides the intended approach-slope indications.

Photometry

APAPI Unit Alignment

Mechanical and optical adjustment of an APAPI unit so its aiming direction and elevation correspond to the approved installation geometry. Alignment is normally checked against the specified approach-slope reference before photometric verification.

Fixtures

Approach Light Base

Physical support or mounting structure used to install an approach-lighting fixture at the specified position and elevation. The base transfers fixture loads to the supporting surface while maintaining the required installation geometry.

Fixtures

Approach Light Circuit

Electrical circuit supplying one or more approach-lighting fixtures or units. The circuit provides the required power path from the lighting control or distribution equipment to the field fixtures and associated connections.

Fixtures

Approach Light Failure

Loss or unacceptable degradation of an approach-lighting fixture's intended light output or operation. The failure may result from lamp or LED failure, wiring, connector, power-supply, optical or mechanical problems.

Fixtures

Approach Light Fixture

Lighting unit installed as part of an approach lighting system to provide a specified visual reference during approach. Its optical assembly, mounting arrangement and light source are selected to produce the required distribution and colour.

Fixtures

Approach Light Maintenance

Inspection, cleaning, adjustment and repair activities performed to keep approach-lighting equipment operational and correctly aligned. Maintenance addresses fixture condition, supports, electrical connections and optical performance as applicable to the installed system.

Maintenance

Approach Lighting Alignment

Geometric adjustment and verification of approach-lighting units relative to the approved runway centreline, elevation and aiming references. Correct alignment ensures the light distribution is directed toward the intended approach sector.

Fixtures

Approach Lighting Barrette

Three or more closely spaced lights arranged in a short transverse line so that, from a distance, they appear as a single short bar of light. Barrettes repeated along the centreline form the main axis of precision approach lighting systems.

Fixtures

Approach Lighting Centerline

Longitudinal reference line formed by the central axis of an approach lighting system. The centreline establishes the primary geometric reference for positioning and alignment of approach-lighting elements.

Fixtures

Approach Lighting Crossbar

Transverse row or assembly of approach-lighting elements extending across the system centreline. The crossbar provides a lateral visual reference whose location and dimensions are defined by the applicable approach-lighting arrangement.

Fixtures

Approach Lighting in LVP

Operation of the approach lighting system during low-visibility procedures, including the required control, monitoring and operational checks for the installed lighting configuration.

Fixtures

Approach Lighting Intensity Control

Control function that changes the commanded intensity of an approach lighting system to provide the required visual brightness for the operating condition. The control acts through the applicable lighting power or control equipment.

Fixtures

Approach Lighting Sequenced Flashing Light

Approach-lighting unit that produces a brief high-intensity flash as part of a timed sequence with other flashing units. The sequence creates a moving visual effect that helps indicate the approach direction toward the runway.

Fixtures

Approach Lighting Spacing

Specified distance between adjacent approach-lighting elements or assemblies along or across the approach system. Spacing establishes the intended visual geometry and must be maintained during installation and inspection.

Fixtures

Approach Lighting Threshold Transition

Defined changeover region where approach-lighting visual guidance transitions to the runway threshold lighting environment. The transition is coordinated with the applicable approach and threshold geometry so pilots receive continuous visual guidance.

Fixtures

Approach Lighting Tower

Elevated support structure on which approach-lighting fixtures are mounted where terrain or obstacles require lights above ground level. Under ICAO Annex 14 approach-light structures must be as low as practicable and frangible, with limited allowances for tall structures, so towers use frangible sections or couplings that break away on impact. Maintenance at height needs approved access and fall-protection practice.

Fixtures

Approach Slope

The descent path an aircraft follows on final approach, indicated visually by systems such as PAPI or defined by instrument procedures.

Operations

Apron

A defined area of an aerodrome intended to accommodate aircraft for purposes such as loading, unloading, passenger embarkation, servicing, parking or maintenance.

Operations

Apron Floodlight

A lighting fixture used to illuminate aircraft parking and servicing areas on an apron while providing the required visual environment for ground operations.

Fixtures

Apron Management Service

An air traffic or ground service function responsible for managing aircraft and vehicle movement on the apron.

Operations

Apron Sign

Sign used to identify or direct movement toward an apron or apron-related destination.

Signage

Apron Taxiway

A taxiway located on or bordering an apron, intended to provide a taxi route across the apron rather than serve as a stand-alone taxiway.

Operations

Arc Flash

A dangerous release of energy from an electrical fault, capable of causing burns and injury, guarded against through safe work procedures, PPE and equipment design.

Electrical

As-Built Drawing

A drawing updated after construction to show the AGL system exactly as installed, including any deviations from the original design.

Documentation

Asset Register

A structured record listing every AGL asset such as fixtures, cable, CCRs and transformers, with identification, location, installation date and status, used for maintenance and lifecycle tracking.

Maintenance

Average IntensityAverage Luminous Intensity

The mean luminous intensity calculated from multiple measurement points across a photometric distribution, used to characterize overall fixture output against a specification.

Photometry

B

Barricading

The use of physical barriers, cones or tape to mark off a work area or hazard on the airside, preventing unauthorised entry by vehicles, personnel or aircraft.

Operations

Base Can

The below-ground metal or composite housing into which a light fixture is mounted, providing a fixed connection point for the fixture and cable.

Fixtures

Beam Axis

The reference line through the beam centre along which a light is aimed. For a symmetrical beam it coincides with the direction of maximum intensity. Used as the reference for aiming and alignment checks.

Photometry

Beam Center

The centre of the main beam, normally the geometric centre of the specified isocandela area, used as the aiming reference. It does not always coincide with the single point of peak intensity (see Peak Intensity), so a test report should state which convention it uses.

Photometry

Beam Spread

The angular width of a light beam, usually measured between the points where intensity falls to a defined fraction of peak, used to characterize how tightly or broadly a fixture distributes light.

Fixtures

Bias Correction

Correction applied to compensate for a known or estimated systematic measurement bias.

Testing

BISBureau of Indian Standards

Bureau of Indian Standards — India's national standards body, publishing Indian Standards (IS) referenced for cables, transformers, enclosures and other electrical components used in AGL installations.

Standards

Black-on-Yellow Sign

Airfield sign with a black legend on a yellow background, used for direction, destination and similar information signs. Location signs use the reverse (yellow on black) and mandatory instruction signs use white on red.

Signage

BOMBill of Materials

An itemised list of every component, quantity and part number required to construct or install an AGL system or subsystem.

Documentation

BOQBill of Quantities

A priced schedule listing the quantities of materials, labour and works items for an AGL project, used for tendering and contract valuation.

Documentation

Brightness Control

A control function used to adjust or select the perceived/photometric light output of a lighting system within its designed operating range.

Systems

C

Cable Bend Radius

Cable Bend Radius is the minimum permissible radius to which an AGL cable may be bent without exceeding the mechanical limits of its construction.

Electrical

Cable Conductor

Cable Conductor is the metallic conductive element within an AGL cable that carries the electrical current or signal required by the circuit.

Electrical

Cable Continuity Test

Cable Continuity Test is an electrical test used to verify that the intended conductive path exists between defined ends of an AGL cable or conductor.

Testing

Cable Duct

Cable Duct is a conduit, duct or enclosed passage used to route and protect AGL cables through pavement, structures or other installation zones.

Electrical

Cable Fault

Cable Fault is an abnormal electrical or physical condition in an AGL cable or associated connection that interrupts, degrades or changes intended circuit performance.

Electrical

Cable Fault Distance

Cable Fault Distance is the estimated distance from a defined cable test point to the location of a detected cable fault or impedance discontinuity.

Testing

Cable Gland

A fitting used to terminate a cable at the point it enters an enclosure, providing a sealed, strain-relieved connection.

Electrical

Cable Insulation

The dielectric material surrounding a conductor that provides electrical separation from other conductors and grounded structures.

Electrical

Cable Joint

A permanent connection made between two cable ends or a cable and a fixture, insulated and sealed to restore the cable's original electrical and mechanical properties.

Electrical

Cable Locator

Cable Locator is an instrument used to detect and trace the route of buried or concealed cables by sensing an applied or induced electrical signal.

Electrical

Cable Marker

A tag or sign, placed along a cable route or at access points, identifying the cable's route, type or ownership for future reference.

Electrical

Cable Megger Test

Cable Megger Test is an insulation-resistance test performed with a megohmmeter to assess cable insulation between specified conductors and/or between a conductor and earth.

Testing

Cable Phase Identification

Cable Phase Identification is the process of positively identifying the corresponding conductor or cable phase at different points in an AGL electrical circuit before connection, testing or maintenance.

Testing

Cable Protection

Cable Protection is the set of mechanical, environmental and electrical measures used to protect AGL cables from damage, excessive stress, moisture and other installation hazards.

Electrical

Cable Pulling Tension

Cable Pulling Tension is the tensile force applied to an AGL cable during installation and pulling through a route, duct or conduit.

Electrical

Cable Repair

The process of restoring a damaged section of cable to a serviceable condition, typically by cutting out the fault and installing a jointed splice or replacement length.

Maintenance

Cable Resistance

The electrical resistance of a cable/conductor path, influenced by conductor material, length, cross-sectional area and temperature.

Electrical

Cable Route

The physical path a cable follows from source to destination, recorded on drawings to guide installation and later locate the cable for maintenance or fault-finding.

Maintenance

Cable Route Marker

Cable Route Marker is a physical marker or sign used to identify the approximate route or location of a buried or concealed AGL cable or associated underground service.

Electrical

Cable Schedule

A tabulated record listing every cable in a project by identification number, origin, destination, type, length and circuit, used for installation and testing reference.

Documentation

Cable Screen

Cable Screen is a conductive shielding layer around one or more cable conductors used to control electromagnetic coupling and, where designed, provide a defined shielding or bonding path.

Electrical

Cable Separation

Cable Separation is the physical or designed separation maintained between AGL cables, circuits and other services to reduce interference, fault propagation, mechanical damage and maintenance risk.

Maintenance

Cable Sheath

Cable Sheath is the protective outer layer of a cable that provides mechanical and environmental protection to the insulated conductors and internal construction.

Electrical

Cable Splice

Cable Splice is an approved connection joining two cable sections while restoring electrical continuity, insulation and environmental protection.

Electrical

Cable Termination

Cable Termination is the prepared end connection of a cable to a connector, terminal, transformer, fixture or other equipment interface.

Electrical

Cable Trench

An excavated, typically backfilled or covered channel used to route and protect buried AGL cables along a defined path, sized to maintain separation between primary, secondary and other services.

Electrical

Calibration Certificate

Documented record showing that an instrument or reference standard was calibrated against specified references under defined conditions.

Testing

Calibration Factor

A correction value applied to raw instrument readings, derived by comparing the instrument's output against a certified reference standard, to bring measurements into agreement with true values.

Testing

Candela

SI unit of luminous intensity in a given direction; symbol cd.

Photometry

CAPACorrective and Preventive Action

A structured process for investigating a nonconformance, correcting it, and implementing changes to prevent recurrence.

Documentation

CAT ICategory I Precision Approach

Precision approach and landing with a decision height not lower than 60 m (200 ft) and either visibility not less than 800 m or runway visual range (RVR) not less than 550 m (ICAO Annex 14 definition of a Category I precision approach runway). Operator and State minima may differ.

Operations

CAT IICategory II Precision Approach

Precision approach and landing with a decision height lower than 60 m (200 ft) but not lower than 30 m (100 ft), and RVR not less than 300 m (ICAO). Needs Category II/III-standard approach, runway centreline and touchdown zone lighting with higher availability and monitoring requirements.

Operations

CAT II AGL

AGL configuration supporting operations under Category II approach/landing criteria, with the required visual aids, control, monitoring and reliability provisions defined by the applicable aerodrome design.

Operations

CAT II/III Lighting System

Integrated AGL arrangement designed to support Category II/III operations, including the specified runway, approach, taxiway, stop-bar and control/monitoring functions.

Operations

CAT IIICategory III Precision Approach

Precision approach and landing in very low visibility. ICAO sub-categories: IIIA (decision height below 30 m / 100 ft or none, RVR not less than 175 m), IIIB (decision height below 15 m / 50 ft or none, RVR below 175 m but not less than 50 m) and IIIC (no decision height and no RVR limit). Lighting reliability, monitoring and maintenance requirements are the most demanding.

Operations

CAT III AGL

AGL configuration supporting Category III low-visibility operations, where lighting availability, redundancy, monitoring, alignment and maintenance controls are critical to continued operational capability.

Operations

CAT III Alignment Verification

Survey/inspection confirming that critical fixtures remain within the approved aiming and positioning tolerances for Category III operation.

Maintenance

CAT III Backup Power

Alternate electrical source or power path provided to maintain required critical lighting functions after loss of the normal source.

Electrical

CAT III Circuit Integrity

Verified electrical continuity, insulation and functional integrity of a critical lighting circuit.

Electrical

CAT III Maintenance Requirement

Maintenance control needed to preserve the availability, alignment, monitoring and redundancy of lighting used for Category III operations.

Maintenance

CAT III Operational Readiness

Verified state in which the required CAT III lighting, power, control, monitoring, maintenance and operational conditions are satisfied.

Maintenance

CAT III Photometric Verification

Measurement of specified critical lighting photometry to demonstrate compliance with the applicable Category III criteria.

Photometry

CAT III Stop Bar Interlock

Control logic preventing an unsafe combination of stop-bar status and movement authorization in a protected low-visibility operation.

Systems

CCRConstant Current Regulator

Constant Current Regulator that maintains controlled current in an airport series circuit despite changes in circuit impedance and load.

Systems

CCR Alarm Reset

Action that acknowledges or clears a CCR alarm indication according to the monitor/control design.

Systems

CCR Auxiliary Supply

Internal or external low-power supply used for CCR control, monitoring, relays, communication or auxiliary functions.

Systems

CCR Cabinet Temperature

Temperature measured or monitored within the CCR enclosure during operation.

Systems

CCR Cabinet Ventilation

Controlled airflow through the CCR enclosure used to manage internal temperature.

Systems

CCR Circuit Insulation

The insulation resistance of a constant-current series circuit's conductors and isolation transformers to earth, verified with a megohmmeter to confirm there is no unintended leakage or fault path.

Systems

CCR Circuit Load

The combined impedance presented by the lamps and isolation transformer primaries wired in series on a circuit, which the CCR's regulator must drive at the selected current step; used to size and verify CCR output capacity.

Systems

CCR Closed-Loop Control

Control method in which measured output current is compared with the reference and corrected to maintain the required regulated value.

Systems

CCR Communication Interface

The data connection (serial, Ethernet, or discrete I/O) between a CCR and an Airfield Lighting Control and Monitoring System (ALCMS) used for remote step selection and status/fault reporting.

Systems

CCR Control Interface

The local or remote control inputs, such as a panel-mounted selector or an ALCMS command, used to choose a CCR's brightness step and on/off state.

Systems

CCR Control Transformer

Transformer supplying an isolated control voltage for CCR control circuitry.

Systems

CCR Cooling Fan

Forced-air cooling component used to remove heat from a CCR cabinet or power electronics.

Systems

CCR Cooling System

The method, such as natural convection, forced-air, or oil-filled construction, used to dissipate heat generated in a CCR's regulating transformer and electronics, sized to the unit's rated output.

Systems

CCR Current Feedback

Signal representing measured output current and returned to the CCR control loop or monitor.

Systems

CCR Current Sensing

Measurement of CCR output current used by the regulator or monitor for control and protection.

Testing

CCR Current Setpoint

The target series-circuit output current commanded for a brightness step. On a 6.6 A (Class 1) circuit a 5-step (Style 2) regulator uses nominal steps of 2.8, 3.4, 4.1, 5.2 and 6.6 A; a 3-step (Style 1) regulator uses 4.8, 5.5 and 6.6 A. On a 20 A (Class 2) circuit the steps are scaled up to 20 A.

Systems

CCR Current Stability

The degree to which a CCR holds its selected output current constant despite input voltage fluctuation or changes in series-circuit load, specified as a tolerance band under AC 150/5345-10.

Systems

CCR Current Transformer

A current transformer used within or alongside a CCR to sense actual output current for feedback regulation and for monitoring and fault-alarm reporting.

Systems

CCR Door Interlock

Interlock that changes or inhibits CCR operation when the cabinet door is opened, where required by the equipment design.

Systems

CCR Electromagnetic Compatibility

Ability of the CCR to operate correctly in its electromagnetic environment without causing or suffering unacceptable interference.

Systems

CCR Emergency Stop

Safety function that rapidly removes or inhibits CCR operation when an emergency stop command is applied.

Systems

CCR Fault Alarm

An indication raised by a regulator monitor, either a standalone L-827 monitor or the monitoring built into an L-829 regulator, when a defined fault such as an open circuit, overcurrent or out-of-tolerance output current is detected in the series circuit.

Systems

CCR Fault Monitoring

The function of detecting, acquiring and reporting CCR abnormal conditions such as protection trips, current deviation, control faults or other defined alarms.

Systems

CCR Fault Reset

Controlled action that clears a latched CCR fault after the underlying cause has been removed or assessed.

Systems

CCR Harmonic Content

Frequency components of CCR input/output waveforms other than the fundamental that contribute to power-quality distortion.

Systems

CCR Heat Sink

Thermal component that transfers heat from power semiconductor devices to the surrounding cooling medium.

Systems

CCR Input Current

Current drawn by the CCR from its electrical supply under the defined operating condition.

Systems

CCR Input Supply

The primary AC power feed, defined by voltage, phase and frequency, delivered to a CCR, as distinct from the regulated constant-current output it produces for the series circuit.

Systems

CCR Intensity Step

One of a CCR's selectable output-current levels; FAA Style 1 regulators provide three brightness steps and Style 2 regulators provide five, each step commanding a defined series-circuit current.

Systems

CCR Local Control

Operation of a CCR from controls mounted at the regulator or vault panel rather than from a remote source, typically used for maintenance or when the communication link to the ALCMS is unavailable.

Systems

CCR Local Remote Selector

Selector determining whether CCR commands are accepted from the local control interface or remote system.

Systems

CCR Maintenance Bypass

Controlled bypass arrangement used to maintain or test a defined function while selected equipment is isolated, only where the approved design permits it.

Testing

CCR Monitor Accuracy

The measurement tolerance, usually expressed as a percentage of reading or full scale, with which a CCR's monitoring circuitry reports output current, voltage and status against a calibrated reference instrument.

Documentation

CCR Open-Circuit Response

The protective action a CCR takes when the series-circuit loop is broken, since circuit resistance rises sharply and the regulator would otherwise drive output voltage up to maintain current; monitors detect this as an open-circuit fault and the CCR trips or limits voltage.

Systems

CCR Output Contactor

The electromechanical switching device within a CCR that connects or disconnects its regulated output to the series circuit, actuated by control commands or fault logic.

Systems

CCR Output Current

Measured current delivered by the CCR into the series circuit during operation.

Systems

CCR Output Current Regulation

The accuracy with which a CCR maintains its rated output current at a selected brightness step, expressed as a percentage tolerance and verified during commissioning against AC 150/5345-10 limits.

Systems

CCR Output Isolation

Electrical isolation between CCR output circuitry and other circuits or accessible parts as required by the equipment design.

Systems

CCR Output Measurement

A reading of a CCR's actual output current and voltage, taken via a digital meter or the regulator's current transformer/monitor, and compared against the specified value for the selected step.

Testing

CCR Output Power

Electrical power delivered by the CCR to the series circuit under the specified load and current step.

Systems

CCR Output Ripple

Periodic variation superimposed on the nominal CCR output current or voltage.

Systems

CCR Output Voltage

CCR output voltage is the voltage developed by the constant-current regulator across the connected series circuit under a defined load and intensity step.

Systems

CCR Overcurrent Protection

A protective function that trips or limits a CCR when its output current exceeds a set threshold, guarding the regulator and downstream isolation transformers from damage.

Systems

CCR Reference Current

Target current value used by the CCR control loop for a selected intensity step.

Systems

CCR Regulator Characteristic

Relationship between CCR control setting and regulated series-circuit output under defined load conditions.

Systems

CCR Regulator Monitor

A device that continuously checks regulator output and series-circuit condition and reports faults such as open circuit, overcurrent or out-of-tolerance current to local or remote control. Under FAA AC 150/5345-10 it is either a standalone L-827 monitor or the monitoring integral to an L-829 regulator; an L-828 regulator has no monitoring.

Systems

CCR Regulator Monitor Interface

Interface through which the CCR regulator and its monitor exchange operating values, alarms and status information.

Systems

CCR Remote Command

Control instruction received from an external ALCMS or control system to change CCR state, step or function.

Systems

CCR Remote Control

A control interface or communication function that allows an authorized command system to select or control CCR operating states remotely.

Systems

CCR Remote Status

Status information transmitted from the CCR to a remote monitoring/control system.

Systems

CCR Short-Circuit Response

The protective action a CCR takes when a low-impedance path bypasses part of the series circuit, since the reduced circuit resistance would otherwise push output current above the setpoint if the regulator did not compensate or trip.

Systems

CCR Soft Start

Controlled rise of CCR output during startup intended to limit transient stress and avoid abrupt current application.

Systems

CCR Status Feedback

The signal a CCR returns to the ALCMS or control panel confirming its present operating state, including on/off, selected brightness step, remote/local mode, and any active fault.

Systems

CCR StepCCR Intensity Step

One selectable CCR operating level that commands a defined series-circuit current and therefore a corresponding lighting intensity.

Systems

CCR Step Accuracy

Closeness of the actual regulated output current to the specified current for a selected CCR step.

Systems

CCR Step Selector

The control, whether a physical switch, relay logic, or software command, used to choose which of a CCR's available brightness steps is applied to the series circuit.

Systems

CCR Step Transition

Change in regulated output current as the CCR moves from one intensity step to another.

Systems

CCR Surge Protection

Lightning and transient-voltage protection, such as surge arrestors, fitted to a CCR's input and output to protect the regulator and connected series circuit from induced surges.

Systems

CCR Thermal Protection

A temperature-sensing protective function that shuts down or derates a CCR if internal components, such as windings or power semiconductors, exceed a safe operating temperature.

Systems

CCR Undervoltage Protection

A protective function that trips or alarms a CCR when its input supply voltage falls below a specified threshold, preventing unstable or out-of-tolerance regulated output.

Systems

Certificate of Conformity

A document issued by a manufacturer or supplier declaring that a product meets the specified standard or contract requirements.

Standards

Changeover Time

Elapsed time required for a power or lighting system to transfer from one source/configuration to another after a defined failure or command.

Electrical

ChockAircraft Wheel Chock

A wedge placed against an aircraft's wheels to prevent it moving while parked.

Operations

Chromaticity

Specification of colour independent of brightness using coordinates derived from a colour space such as CIE chromaticity diagrams.

Photometry

Chromaticity Coordinates

The x,y values on the CIE chromaticity diagram that define a light's exact colour, used to verify a fixture's output falls within the colour boundaries specified for its signal type.

Photometry

Circuit Breaker

A resettable protective switching device that interrupts an electrical circuit when specified overcurrent or fault conditions occur.

Electrical

Circuit Breaker Coordination

Circuit Breaker Coordination is the engineering process of selecting and setting protective devices so a fault is cleared by the nearest appropriate protective device while maintaining service to unaffected portions of the electrical system.

Electrical

Circuit Identification

The labelling and record-keeping system used to uniquely identify each AGL circuit, fixture or cable run so it can be located, tested and maintained without confusion with adjacent circuits.

Testing

Circuit Load

The electrical demand connected to a circuit, expressed through the current/power characteristics used for design and equipment selection.

Electrical

Circuit Resistance

The total electrical resistance of a series lighting circuit's conductors, terminations and transformer primaries; the CCR must develop enough output voltage to force its set current through this resistance, so it is checked by loop or insulation-resistance testing.

Testing

Clamp Meter

An electrical measuring instrument that measures current through a conductor using a clamp around the conductor, reducing the need to open the circuit.

Electrical

Closed Marking (X)

A cross displayed at each end of a closed runway or taxiway, or portion of one, to show the surface is unusable. ICAO specifies white on a runway and yellow on a taxiway; FAA practice uses yellow crosses. Lighting on a closed surface should not be operated.

Signage

Color Rendering Index

A measure of how accurately a light source reveals the true colours of illuminated objects compared with a reference light source, expressed on a scale up to 100.

Photometry

Colorimetry

The measurement and specification of light colour, typically expressed as chromaticity coordinates or dominant wavelength, used to verify AGL fixtures emit the correct colour for their function.

Testing

Combined Standard Uncertainty

The overall standard uncertainty of a measurement result, obtained by combining individual input uncertainty components in quadrature (root-sum-of-squares) per the GUM uncertainty framework.

Testing

Commissioning

The structured process of inspecting, testing, adjusting and verifying installed equipment or systems so they can be placed into intended service.

Testing

Commissioning Report

A document recording the tests, measurements and checks performed before an AGL system is handed over, confirming it meets the specified performance criteria.

Testing

Communication Cable

Cable used to carry data signals, such as between the ALCMS and field CCRs, as distinct from power cable.

Systems

Compliance Assessment

The process of comparing measured or observed results against a specification, standard or acceptance criterion to determine whether an item passes or fails.

Standards

Compliance Matrix

A table cross-referencing project or system requirements against the specific standard clauses or design features that satisfy them, used to demonstrate compliance.

Standards

Condition-Based Maintenance

Maintenance triggered by the measured or observed condition of equipment, such as declining photometric output or rising insulation resistance, rather than by a fixed time interval.

Maintenance

Conditional Clearance

Movement clearance containing conditions that must be satisfied before the aircraft or vehicle may proceed.

Operations

ConduitCable Conduit

A tube, rigid or flexible, used to enclose and protect a cable during and after installation.

Electrical

Confidence Interval

Statistical interval associated with an estimated parameter and a stated confidence level under the adopted statistical model.

Photometry

Conflict Alerting

Conflict Alerting is a surface-movement safety function that identifies potentially conflicting aircraft or vehicle movements from available surveillance and system data and generates an operational alert according to approved system logic.

Operations

Connector Kit

A pre-packaged set of components, connector body, seals and boots, used to make a standard field-installed cable connection, typically an L-823 style connector.

Electrical

Connector Replacement

The removal and replacement of a worn, damaged or corroded cable connector to restore a reliable electrical connection.

Electrical

Contactor

An electrically controlled switching device used to make or break a power circuit under defined operating conditions.

Electrical

Continuity Test

A test used to verify that the intended conductive path has sufficiently low resistance and is electrically continuous.

Testing

Control Cable

Cable carrying low-voltage control or signalling connections, such as between a CCR and its remote control panel.

Systems

Control Panel

An enclosure containing electrical/control components used to distribute, switch, protect, interface or control the associated AGL equipment.

Electrical

Corrective Action

An action taken to eliminate the root cause of an identified nonconformance, distinct from a quick fix that addresses only the symptom.

Maintenance

Corrective Maintenance

Maintenance carried out in response to an identified fault or failure, to restore equipment to working condition.

Maintenance

Correlated Color Temperature

A single-number description, in kelvins, of the colour appearance of a white light source, used mainly for apron floodlighting or white LED fixtures rather than coloured aeronautical signal lights.

Fixtures

Coverage Factor

Multiplier used to obtain expanded uncertainty from combined standard uncertainty.

Testing

Critical Area

A protected area around a navigational aid, such as an ILS, within which vehicles, aircraft or structures must not enter or park when the aid is in use, to avoid signal interference. See also: ILS Critical Area; ILS Sensitive Area.

Operations

Critical Lighting Circuit

AGL circuit whose availability is essential to a defined operational function, especially during low-visibility operations.

Electrical

Critical Lighting Equipment

AGL equipment whose failure can directly affect a required operational lighting function.

Operations

Current Regulation

A CCR's core function of holding its output current fixed at the selected step regardless of the resistance the connected series circuit presents, which is what keeps every lamp on the circuit at uniform brightness.

Systems

Cutoff Angle

The angle above which a fixture is designed to emit no light, used to control glare and stray light outside the intended beam.

Fixtures

D

Data ValidationPhotometric Data Validation

The process of checking recorded photometric, electrical or inspection data for errors, out-of-range values or inconsistencies before it is accepted into a report or record.

Photometry

Deep Base

A base can with a greater burial depth, typically used for elevated fixtures or where ducting requires additional clearance.

Fixtures

Destination Sign

Sign identifying a destination such as an apron, terminal area, cargo area or other operational destination.

Signage

DGCADirectorate General of Civil Aviation

Directorate General of Civil Aviation — India's civil aviation safety regulator, responsible for aerodrome licensing and enforcement of Indian requirements for AGL performance and maintenance.

Standards

Dielectric TestDielectric Withstand Test

A test in which insulation is subjected to a specified electrical stress to verify dielectric withstand.

Testing

Dimensional Inspection

Measurement of specified physical dimensions and comparison with the approved drawing, standard or acceptance criterion.

Testing

Dimming

Controlled reduction or adjustment of light output by changing the operating condition of the lighting source or driver.

Systems

Direction Sign

Sign providing directional information toward one or more taxiways, runways, aprons or other aerodrome destinations.

Signage

Discrimination

Ability of protective devices to distinguish fault conditions and isolate the intended section without unnecessary upstream interruption.

Electrical

Displaced Threshold

A runway threshold located at a point other than the physical start of the runway, reducing the usable landing distance while the full length remains available for takeoff or roll-out.

Operations

Document Control

The system of numbering, versioning, approval and distribution used to manage project drawings, reports and records so the correct revision is always in use.

Documentation

DuctCable Duct

A pipe or channel, installed underground, through which cables are pulled and protected.

Electrical

Dynamic Taxi Routing

Generation or modification of a taxi route in response to traffic, closures, operational constraints or system conditions.

Systems

E

Earth Electrode

A conductive element installed in contact with soil to provide the connection between an earthing system and the general mass of earth.

Electrical

Earth PitEarth Pit / Grounding Pit

An enclosure or accessible point used to house/protect an earth electrode connection and facilitate inspection or testing of the grounding system.

Testing

Efficiency Test

A test measuring the ratio of useful output, light or power, to input power for a fixture, transformer or CCR, to verify it meets its rated efficiency.

Testing

Electrical Clearance

The minimum required physical distance between an energised conductor or component and another object, person or structure, maintained to prevent flashover or contact.

Electrical

Electrical Safety

The set of practices, procedures and equipment used to prevent injury from contact with, or proximity to, energised electrical equipment.

Documentation

Electrical Test

A general term for tests such as insulation resistance, continuity, voltage and current, performed to verify the electrical integrity of an AGL circuit or component.

Testing

Elevated Light Fixture

An AGL light fixture mounted above the pavement on an approved support or mounting arrangement to provide the required visual indication.

Fixtures

Emergency Stop

A manually initiated safety function intended to place affected equipment into a defined safe or stopped state during an emergency.

Operations

Environmental Test

A controlled test exposing equipment to specified environmental conditions to verify the required performance or durability.

Testing

Equipotential Bonding

Electrical bonding that connects conductive parts together so that potential differences between them are minimized under normal or fault conditions.

Electrical

Ethernet

Ethernet is a family of wired computer-networking technologies used to exchange digital data between networked devices through defined physical and data-link communication methods.

Systems

Event Log

A chronological record of alarms, faults, switching operations or other system events captured by the ALCMS or CCR controller. See also: ALCMS Event Log.

Documentation

Expanded Uncertainty

Measurement uncertainty obtained by multiplying the combined standard uncertainty by a stated coverage factor.

Testing

F

FAAFederal Aviation Administration

Federal Aviation Administration — the United States civil aviation authority, whose AC 150 series Advisory Circulars on airport lighting are widely referenced internationally for AGL equipment and installation practice.

Standards

FAA AC 150/5340 SeriesFAA Advisory Circular 150/5340 Series

FAA Advisory Circular series covering airport visual aids: standards and guidance for the design, installation and maintenance of airport markings, signs and lighting. Equipment specifications sit in the AC 150/5345 series.

Standards

FAA AC 150/5345 SeriesFAA Advisory Circular 150/5345 Series

FAA Advisory Circular series specifying airport lighting equipment such as constant current regulators, isolation transformers, connectors and lighting control and monitoring systems.

Standards

FAA AC 150/5345-26EFAA Specification for L-823 Plug and Receptacle, Cable Connectors

FAA specification (edition E, issued December 2021) for L-823 plug and receptacle cable connectors used with underground power cables, isolation transformer leads and light fixture leads. Confirm the edition in force before citing.

Standards

FAA AC 150/5345-47CFAA Specification for Series to Series Isolation Transformers

FAA specification (edition C, July 2011) for series-to-series isolation transformers used in airport lighting systems, including their L-830 type ratings by wattage and current. Confirm the edition in force before citing.

Standards

Factory Acceptance Test

A controlled test performed at the manufacturer or approved facility to verify specified equipment functions and performance before shipment or site installation. See also: FAT.

Testing

Factory Inspection

An inspection of equipment or materials carried out at the manufacturer's premises, before shipment, to verify build quality and specification compliance.

Maintenance

Fail-Safe Lighting Arrangement

Lighting/control arrangement designed so that a defined failure drives the system toward a predetermined safe condition.

Systems

FATFactory Acceptance Test

The formal test event, held at the manufacturer's works, where the purchaser or their representative witnesses equipment performance against the agreed test procedure before shipment. See also: Factory Acceptance Test.

Testing

Fault Log

A record listing each fault detected on an AGL system, including date, description, affected circuit and corrective action taken.

Maintenance

Fiber Optic Cable

Cable using optical fiber to carry data signals over long distances with immunity to electrical interference, increasingly used for AGL monitoring and control networks.

Electrical

Field Photometry

Field photometry is the measurement of the photometric performance of installed aerodrome lighting equipment at the airport using calibrated instruments and defined measurement geometry.

Photometry

FilterOptical Filter

A component fitted to a fixture to alter its transmitted light, most commonly a coloured filter used to produce a specific aeronautical signal colour from a white light source.

Fixtures

Final Inspection

The last inspection performed on completed work or equipment before handover, confirming all outstanding items from earlier inspections have been closed.

Maintenance

Fixture Alignment

The adjustment of a fixture's aiming angle back to its design position, carried out when inspection finds it has shifted out of tolerance.

Maintenance

Fixture Base Installation

The installation of an AGL fixture's mounting base or can, set to the correct depth, level and orientation before the fixture itself is fitted.

Fixtures

Fixture Cable Entry

The point and method by which a supply cable enters a fixture housing, sealed to maintain the enclosure's ingress protection rating.

Fixtures

Fixture Cleaning

The removal of dirt, dust or contamination from a fixture's lens, reflector or prism to restore its rated light output.

Fixtures

Fixture Connector Sealing

The sealing of a fixture's electrical connector, typically an L-823/L-830 style waterproof coupling, to prevent moisture ingress at the joint.

Fixtures

Fixture Drainage

Provision within a fixture base or housing to allow water to drain away rather than collect around cable entries and connectors.

Fixtures

Fixture Elevation

The height of an in-pavement or elevated fixture relative to the surrounding surface, controlled to meet frangibility and photometric siting requirements.

Fixtures

Fixture Fastener

The bolts, screws or clips used to secure a fixture to its base or mounting, tightened to the manufacturer's specified torque.

Fixtures

Fixture Frangible Mounting

A mounting design that allows a fixture to break away cleanly on impact, reducing damage to an aircraft that strikes it.

Fixtures

Fixture Functional Check

A quick verification, usually visual and electrical, that an installed or maintained fixture illuminates and operates as intended.

Fixtures

Fixture Grouting

The filling of the annular gap around an in-pavement fixture base with grout, providing a stable, level surface and reducing water ingress.

Fixtures

Fixture Housing

The outer body of a light fixture, providing structural support, weatherproofing and mounting for the internal optical and electrical components.

Fixtures

Fixture Identification

The unique reference, tag, serial number or location code assigned to each AGL fixture so it can be tracked through installation, testing, maintenance and replacement.

Testing

Fixture Leveling

Adjustment of a fixture during installation so its top surface sits flush with, and parallel to, the surrounding pavement.

Fixtures

Fixture Optical Cleaning

Cleaning of a fixture's lens or optical surfaces to remove dirt, rubber deposits or film that would otherwise reduce light output.

Fixtures

Fixture Orientation

The rotational alignment of a fixture's beam relative to the runway or taxiway centreline, set to meet the required azimuth.

Fixtures

Fixture Reinstallation

The refitting of a fixture into its base after removal for maintenance, repair or replacement.

Maintenance

Fixture Replacement

The removal of a failed or end-of-life fixture and its substitution with a new or refurbished unit of the correct type.

Fixtures

Fixture Seating

The correct, fully engaged fit of a fixture into its base or mounting, confirmed before final fastening.

Fixtures

Fixture Torque

The tightening force applied to a fixture's fasteners, specified by the manufacturer to secure the unit without damaging the housing or seal.

Fixtures

Fixture Visual Inspection

A visual examination of an installed fixture's condition, alignment, cleanliness and physical damage.

Maintenance

Fixture Water Ingress

Water entry into a fixture housing or connector, typically through a failed seal, that can damage optics, electronics or insulation.

Fixtures

FODForeign Object Debris / Foreign Object Damage

Foreign Object Debris is material or an object in the aviation environment that can create a hazard or cause damage; Foreign Object Damage is the resulting damage.

Operations

FOD ControlForeign Object Debris Control

The procedures used to prevent, detect and remove foreign object debris from the movement area.

Documentation

FOD Prevention

Measures taken to prevent foreign object debris, such as loose fasteners, tools or materials, from being left on or entering the movement area, where it could damage aircraft or engines.

Operations

Follow-Me Vehicle

A marked airside vehicle used to guide an aircraft, typically on the ground, from the runway to its parking position or vice versa.

Operations

Foreign Object Inspection

Foreign Object Inspection is a systematic inspection of the movement area and associated work areas to identify foreign objects, debris or conditions that could damage aircraft, vehicles, personnel or airport infrastructure.

Maintenance

Frangible Coupling

A mounting designed to break away cleanly under impact, reducing the risk of damage to an aircraft that strikes an elevated fixture such as an approach light tower.

Fixtures

Frequency Variation

Variation of the AC supply frequency from its nominal value. In AGL systems, frequency variation can affect equipment designed for a specific supply frequency and should be evaluated against the applicable equipment specification.

Electrical

Functional Test

A test that verifies the intended operation of a system or component through its specified command, response, indication and protective functions.

Testing

Fuse

An overcurrent protective device that opens its circuit when the current exceeds its specified operating characteristic.

Electrical

G

Gasket

A sealing component fitted between two mating surfaces of a fixture or enclosure to prevent water and dust ingress.

Fixtures

Goniophotometer

Photometric instrument/system that measures light output as a function of direction by controlling or measuring angular position.

Photometry

GPUGround Power Unit

A mobile or fixed unit supplying electrical power to a parked aircraft so its engines and APU can remain shut down. See also: Ground Power Unit.

Electrical

Ground Movement Display

An air traffic control workstation display, typically fed by surface surveillance such as A-SMGCS, showing aircraft and vehicle positions, taxi routes and lighting or guidance status across the movement area.

Systems

Ground Power Unit

A mobile or fixed unit supplying electrical power to a parked aircraft so its engines and APU can remain shut down while systems stay powered. See also: GPU.

Electrical

Grounding

The electrical practice of establishing a conductive reference or fault-current path to ground/earth as required by the applicable electrical design.

Electrical

Guidance Function

Function that provides route or movement guidance to an aircraft or vehicle using system information and available visual aids.

Operations

Guidance Status Feedback

Feedback indicating whether the commanded guidance state has been achieved and is being monitored.

Systems

H

Halogen Lamp

An incandescent-type lamp containing halogen gas, which extends filament life and maintains more consistent light output compared with a standard incandescent lamp, used in some AGL fixtures.

Fixtures

HandholeCable Handhole

A shallow, below-grade access enclosure, smaller than a manhole, installed along an underground duct route to permit cable jointing, transformer housing, or inspection without excavation.

Electrical

Harmonic Distortion

Distortion of an AC waveform caused by harmonic components relative to the fundamental frequency.

Electrical

Hazard Identification

The process of recognising conditions or activities that could cause harm, carried out before work begins so risks can be assessed and controlled.

Operations

Heat Sink

A component, typically finned metal, designed to conduct heat away from an LED module or electronic component and dissipate it to the surrounding air.

Fixtures

HIALSHigh Intensity Approach Lighting System

High Intensity Approach Lighting System providing high-intensity approach visual guidance to support the transition from instrument approach to runway visual reference.

Fixtures

High Voltage Test

A dielectric withstand test in which a voltage above normal operating level is applied to a cable or component to confirm its insulation can withstand system voltage without breakdown. See also: HV Test.

Testing

HIRLHigh Intensity Runway Lights

High Intensity Runway Lights (HIRL) provide high-intensity runway-edge guidance for operations requiring enhanced visual conspicuity.

Fixtures

HMIHuman-Machine Interface

A Human-Machine Interface (HMI) is the operator interface through which users view system status, alarms and controls and issue commands to an automated system.

Systems

Holding Bay

A defined area where aircraft can be held, or bypassed, to make surface movement more efficient (ICAO). It is often a widened area beside a taxiway near a runway entrance.

Operations

Humidity Test

A controlled environmental test used to assess equipment performance or insulation/sealing behaviour under specified humidity conditions.

Testing

HV TestHigh Voltage Test

A high-voltage electrical test in which a specified test voltage is applied to verify the withstand or insulation condition of the equipment/circuit under the approved procedure. See also: High Voltage Test.

Testing

HV TesterHigh Voltage Tester

A test instrument designed to apply or measure high-voltage test conditions for specified electrical insulation or dielectric tests.

Testing

I

ICAOInternational Civil Aviation Organization

International Civil Aviation Organization — the UN specialized agency that sets international Standards and Recommended Practices (SARPs) for aerodrome design and operation, including AGL, chiefly through Annex 14.

Standards

ICAO Annex 14ICAO Annex 14 Aerodromes

The ICAO annex governing aerodrome design and operations; Volume I sets the core international standards and recommended practices for AGL siting, photometric performance and reliability.

Standards

Identification Beacon

A beacon that provides a coded or distinctive visual signal used to identify the aerodrome or facility.

Fixtures

Identification Function

Function that associates a detected surface target with an aircraft, vehicle or other operational identity.

Operations

IECInternational Electrotechnical Commission

International Electrotechnical Commission — publishes international electrical and electronic equipment standards, several of which underpin AGL power supply, cabling and equipment design.

Standards

IEC 60364IEC 60364 series for low-voltage electrical installations

IEC standard series for low-voltage electrical installations, referenced for cabling, protection and earthing practice on AGL power circuits.

Standards

IEC 60598IEC 60598 series for luminaires

IEC 60598 is a family of standards for luminaires and related requirements; its applicability to a particular airport light depends on the product construction and the governing AGL specification.

Standards

Illuminance

Photometric quantity equal to luminous flux incident on a surface per unit area.

Photometry

ILS Critical AreaInstrument Landing System Critical Area

A protected ground area around an Instrument Landing System antenna, within which vehicle and aircraft movement is restricted when the ILS is in use by an aircraft on approach, to prevent signal reflection or blockage. See also: Critical Area; ILS Sensitive Area.

Operations

ILS Sensitive AreaInstrument Landing System Sensitive Area

An area extending beyond the ILS critical area where the parking or movement of aircraft and vehicles is controlled to prevent unacceptable interference with the ILS signal, particularly during low-visibility operations.

Operations

In-Process Inspection

An inspection carried out during manufacture or installation, rather than at the start or end, to catch defects before further work is built on top of them.

Maintenance

Incandescent Lamp

A traditional lamp producing light from a heated filament, still found in some older AGL fixtures ahead of LED conversion.

Fixtures

Incoming InspectionIncoming Material Inspection

An inspection performed on materials or equipment when they arrive on site, checking for transport damage and confirming they match the order and specification.

Maintenance

Indian Standard (IS)

An Indian Standard (IS) is a standard published by the Bureau of Indian Standards for a defined product, material, process, test method or other subject.

Standards

Information Sign

Sign providing operational information that does not itself constitute a mandatory instruction or movement clearance.

Signage

Inset CleaningInset Light Cleaning

Cleaning specifically of inset, flush-mounted fixtures, whose recessed lenses are prone to collecting rubber deposits, dirt and standing water.

Fixtures

Inset Light Fixture

An AGL light fixture designed for installation substantially flush with the pavement surface, with its optical, mechanical and load characteristics controlled by the applicable fixture design.

Fixtures

Inspection Report

A document recording the findings of a physical or functional inspection of AGL equipment against a checklist or specification.

Maintenance

Inspection Test PlanInspection and Test Plan

A document listing every inspection and test required for a scope of work, in sequence, identifying who performs each one and which are hold or witness points.

Testing

Instrument Identification

The recording of the make, model and calibration status of the test instrument used for a given measurement, so results can be traced to a verified instrument.

Testing

Instrument Warm-Up

The period a photometric or electrical test instrument is allowed to stabilise after power-up before readings are taken, required because sensor and electronic drift settle over time.

Testing

Insulation Breakdown

Loss of dielectric integrity allowing excessive leakage or an unintended conductive path through the insulation system.

Electrical

Insulation Coordination

The design process of selecting insulation levels and surge protection so that, under overvoltage conditions, protective devices operate before insulation is damaged.

Electrical

Insulation Monitoring

Monitoring of insulation condition or leakage to detect deterioration that could compromise electrical isolation or cause an earth fault.

Electrical

Insulation Test

A megohmmeter test measuring the insulation resistance of a cable or winding, used to detect insulation degradation or moisture ingress before energising.

Testing

Intensity Step

A defined selectable operating level of an AGL lighting system that corresponds to a controlled light-output condition, commonly selected through the CCR/control system.

Systems

Inter-Instrument Comparison

Comparison of measurements from two or more instruments measuring the same reference or test item.

Testing

Interlock

A control or protection function that prevents or constrains an operation when a specified permissive or safe condition is not present.

Systems

Intermediate Holding Position

Intermediate Holding Position is a designated position on a taxiway where an aircraft or vehicle may be required to hold for traffic sequencing or control, distinct from a runway holding position.

Operations

Intermittent FaultIntermittent Electrical Fault

A fault that appears and disappears as a function of movement, temperature, moisture, vibration, loading, switching or another changing condition.

Maintenance

IP RatingIngress Protection Rating

An enclosure protection classification defining the degree of protection against ingress of solids and water according to the applicable IP classification standard.

Standards

ISO 9001Quality Management Systems

International standard for quality management systems, often required of AGL manufacturers and contractors as evidence of consistent process control and product quality.

Standards

Isolating Transformer

Series-to-series isolation transformer used to electrically isolate an individual airport-lighting load from the primary series circuit while transferring power to the secondary load. Called an isolation transformer in FAA documents. See also: Transformer Primary; Transformer Secondary.

Electrical

Isolation Transformer Connector Lead

The short factory-terminated cable segment, primary or secondary, that extends from the isolation transformer's potted winding to the L-823 plug or receptacle used to join it into the series or fixture circuit.

Electrical

Isolation Transformer Continuity Test

A test verifying an unbroken electrical path through the isolation transformer's primary and secondary windings, typically performed with an ohmmeter before energizing or re-energizing a series circuit.

Testing

Isolation Transformer Dielectric Test

A hipot (high-potential) test applying an elevated AC or DC voltage between a transformer's primary and secondary windings, and between windings and ground, to confirm the insulation withstands its specified test voltage without breakdown.

Testing

Isolation Transformer Fault

A failure condition in an isolation transformer, such as an open or shorted winding, insulation breakdown, or moisture ingress, that interrupts or degrades power transfer to the connected fixture.

Electrical

Isolation Transformer Housing

The potted or resin-encapsulated enclosure that protects an isolation transformer's core and windings from moisture and mechanical damage in its below-grade or in-base installation.

Electrical

Isolation Transformer Impedance

The transformer's internal opposition to current flow, arising from winding resistance and leakage reactance, which affects voltage regulation and current transfer between the series circuit and the connected fixture.

Electrical

Isolation Transformer Insulation

The dielectric material, potting compound and winding insulation that electrically isolates the primary series circuit from the secondary fixture circuit and withstands the transformer's rated test voltage.

Electrical

Isolation Transformer Moisture Ingress

Water intrusion into a transformer housing or connector interface, typically through a failed seal, that degrades insulation resistance and can progress to an insulation or dielectric fault.

Electrical

Isolation Transformer Polarity

The defined orientation relationship between an isolation transformer's primary and secondary windings, relevant to correct lead connection during installation and replacement.

Electrical

Isolation Transformer Primary

The isolation transformer winding connected directly into the constant-current series circuit; it carries the regulated series-circuit current, such as 6.6 A or 20 A.

Electrical

Isolation Transformer Secondary

The winding connected to the individual light fixture. It supplies the lamp or LED-driver current at the voltage that fixture needs, while staying electrically isolated from the series circuit.

Electrical

Isolation Transformer Temperature Rise

The increase in winding temperature above ambient under rated load, measured to confirm the transformer's thermal design stays within its insulation class limits.

Electrical

Isolation Transformer Turns Ratio

The ratio of primary to secondary winding turns. For a 6.6 A series circuit feeding a 6.6 A lamp the ratio is typically 1:1 (6.6 A / 6.6 A); other types, such as 20 A / 6.6 A units on 20 A circuits, step the series current down to the lamp current.

Electrical

Isolation Transformer VA Rating

The transformer's rated apparent power capacity in volt-amperes, sized to match or exceed the connected fixture's load without exceeding the transformer's thermal limits.

Electrical

ITP Hold PointInspection Test Plan Hold Point

A stage in an Inspection Test Plan beyond which work may not proceed until a specified party has inspected and formally released it.

Testing

J

Jet BridgePassenger Boarding Bridge

A movable, enclosed passenger bridge connecting a terminal gate to an aircraft door.

Operations

K

kcmilThousand Circular Mils, MCM

A unit used to specify the cross-sectional area of large power cable conductors, commonly used for primary feeder cables supplying series airfield lighting circuits.

Electrical

KelvinK, Colour Temperature

SI base unit of thermodynamic temperature, symbol K. In lighting it is the unit used to state correlated colour temperature: lower values look warm (yellowish), higher values cool (blue-white).

Photometry

Key-Operated Switch

A control switch requiring a physical key to change state, used at constant current regulators or control panels to restrict unauthorised operation of airfield lighting circuits.

Electrical

kVA RatingKilovolt-Ampere Rating

The apparent power rating of a constant current regulator, isolating transformer or other electrical equipment, expressed in kilovolt-amperes.

Electrical

L

L-823 ConnectorFAA L-823 Connector

Standardized plug/receptacle cable connector used to make detachable electrical connections in airport lighting circuits.

Electrical

L-823 Connector Cable Preparation

The process of stripping, measuring and dressing a cable end to the dimensions specified in AC 150/5345-26, prior to crimping and assembling an L-823 plug or receptacle onto it.

Electrical

L-823 Connector Contact

The metal pin or socket element inside an L-823 plug or receptacle body that makes the electrical connection when the two halves are mated.

Electrical

L-823 Connector Contact Resistance

The electrical resistance measured across a mated L-823 connector's contacts; elevated resistance indicates corrosion, a poor crimp, or contact wear, and can cause localized heating or circuit faults.

Electrical

L-823 Connector Crimp

The mechanical compression joint made between a cable conductor and an L-823 contact using a specified crimping tool and die, forming the connector's primary electrical and mechanical connection.

Electrical

L-823 Connector Field Installation

The on-site assembly of an L-823 connector kit onto cable ends, including cable preparation, crimping, contact insertion and boot/seal closure, performed per the manufacturer's instructions and AC 150/5345-26.

Electrical

L-823 Connector Identification

The style, class and type markings molded or stamped onto an L-823 connector body (e.g., "L-823, Style 3") that identify its configuration for correct mating and replacement.

Electrical

L-823 Connector Insulation

The connector body and boot material, typically an elastomer, providing dielectric separation and environmental sealing around the mated contacts.

Electrical

L-823 Connector Mating

The act of joining an L-823 plug and receptacle so their internal contacts engage and complete the circuit; correct mating also compresses the connector's watertight seal.

Electrical

L-823 Connector Moisture Protection

The sealing boot, gel fill or heat-shrink covering applied over a mated L-823 connector to prevent water ingress into the below-grade splice.

Electrical

L-823 Connector Plug

The male half of an L-823 connector pair, typically terminating the fixture or transformer lead, that inserts into the corresponding receptacle.

Electrical

L-823 Connector Receptacle

The female half of an L-823 connector pair, typically terminating the circuit cable, into which the corresponding plug is inserted.

Electrical

L-823 Connector Replacement

The removal and substitution of a damaged, corroded or failed L-823 connector, including cable re-preparation and re-crimping, to restore a low-resistance, sealed connection.

Electrical

L-823 Connector Sealing

The final step in connector assembly, where a boot, tape, gel or heat-shrink sleeve is applied to exclude moisture from the mated connector and cable entry points.

Electrical

L-823 Connector Visual Inspection

A physical examination of an L-823 connector for cracking, discoloration, corrosion, seal damage or incomplete mating, typically performed during scheduled maintenance or fault investigation.

Maintenance

L-824 CableFAA L-824 Cable

Cable manufactured to FAA specification L-824, the standard for airport lighting cable used in series circuits.

Standards

Laboratory Photometry

Photometric testing of a fixture performed on a goniophotometer under controlled indoor conditions, as opposed to field measurements taken on the installed system.

Photometry

Ladder Safety

Practices governing the safe selection, inspection and use of ladders, applicable when accessing elevated AGL equipment such as approach lighting towers.

Maintenance

Lamp Life

The rated operating hours a lamp is expected to provide before failure or before its output falls below a defined threshold, used to plan replacement intervals.

Fixtures

Lamp Replacement

The removal of a failed or degraded incandescent or halogen lamp and its replacement with a new one of the correct rating.

Fixtures

Layout Drawing

A drawing showing the physical arrangement of AGL fixtures, cables and equipment across the aerodrome, used for installation and reference.

Documentation

Leakage Current

Small current that flows through insulation or to earth under normal operation, monitored because an abnormal increase indicates insulation degradation.

Electrical

LED Array

A grouping of multiple individual LED emitters mounted together within a fixture's light engine, combining their output to produce the required total luminous intensity.

Fixtures

LED Chromaticity Shift

A change in an LED source's emitted color coordinates over its operating life, usually from phosphor or semiconductor aging, which can move the fixture's output outside its specified color box.

Photometry

LED Color Stability

The degree to which an LED light source maintains consistent chromaticity and intensity over its service life and across its operating temperature range.

Fixtures

LED Degradation

The gradual reduction in light output of an LED source over its operating life, tracked to predict when a fixture will fall below its minimum intensity requirement.

Fixtures

LED Dimming

The controlled reduction of an LED fixture's output, achieved by lowering drive current or through pulse-width modulation, used to implement the fixture's brightness steps within a CCR-regulated series circuit.

Fixtures

LED Driver

LED Driver is an electronic power-conversion/control component that supplies the LED light source with the electrical conditions required for stable and controlled operation.

Fixtures

LED Driver Current

The regulated current supplied by an LED fixture's internal driver circuit to its LED array, matched to the LEDs' rated forward current to achieve correct output and lifespan.

Fixtures

LED Driver Replacement

The removal and substitution of a failed or degraded LED driver module within a fixture, restoring correct current regulation to the LED array.

Fixtures

LED Environmental Rating

The ingress protection (IP) and temperature or vibration rating of an LED fixture, specifying its suitability for the below-grade or exposed outdoor conditions found in airfield lighting installations.

Fixtures

LED Failure Mode

The characteristic way an LED fixture degrades or fails, such as gradual lumen depreciation, individual emitter dropout, or driver failure, as distinct from the abrupt filament failure typical of incandescent lamps.

Fixtures

LED Harmonic Distortion

Distortion of the current waveform drawn by an LED driver from the series circuit, which must be kept within limits so it does not interfere with CCR regulation or other equipment on the circuit.

Fixtures

LED Heat Sink

The thermally conductive structure, typically metal, that conducts heat away from an LED array's junction to the fixture body or ambient air, limiting junction temperature to preserve output and lifespan.

Fixtures

LED Inrush Current

The brief current surge drawn by an LED driver at the moment power is applied or a series circuit is energized, which the CCR and protection equipment must tolerate without nuisance tripping.

Fixtures

LED Intensity Control

The mechanism, whether analog current reduction or digital signaling, by which an LED fixture's brightness is set to match the series circuit's commanded intensity step.

Fixtures

LED Junction Temperature

The temperature at the semiconductor junction inside an LED emitter; the key parameter governing its light output, efficiency and long-term reliability.

Fixtures

LED Lens

The optical element, often a precision-molded polymer lens, that shapes an LED fixture's raw emitter output into the required beam pattern and intensity distribution.

Fixtures

LED Lifetime

The rated operating life of an LED light source, typically expressed as hours to a specified lumen-maintenance threshold such as L70, generally far exceeding that of incandescent lamps.

Fixtures

LED Light Engine

The integrated assembly of LED array, driver electronics, heat sink and optics that together produce a fixture's specified photometric output.

Fixtures

LED Light Source

A solid-state light source based on light-emitting diodes used to generate controlled optical output in an AGL fixture.

Fixtures

LED Module

A pre-assembled unit combining LED sources, driver electronics and optics, designed as a replaceable light-source assembly within a fixture.

Fixtures

LED Module Replacement

The removal and substitution of a complete LED light engine or module in a fixture, typically handled as a single field-replaceable unit rather than individual component repair.

Fixtures

LED Optical Efficiency

The proportion of an LED source's generated light that is successfully directed into the fixture's useful beam by its lens or reflector, after accounting for optical losses.

Fixtures

LED Optical Module

The lens, reflector and associated optical housing that shapes an LED light engine's output into the fixture's required beam pattern.

Fixtures

LED Prism

A refractive optical element used in some LED fixture designs to redirect or shape light output where a simple lens alone cannot achieve the required distribution.

Fixtures

LED Redundancy

A fixture design feature in which multiple LED emitters or circuits operate in parallel, so a single emitter's failure causes only a partial, rather than total, loss of fixture output.

Fixtures

LED Reflector

A shaped, reflective optical surface within a fixture that redirects LED emitter output into the required beam pattern, often used together with, or instead of, a lens.

Fixtures

LED Replacement

The removal and replacement of a failed or degraded LED light source or module.

Fixtures

LED Retrofit

The replacement of a legacy incandescent or halogen airfield light fixture's lamp and optical assembly with an LED light engine, while reusing the existing base can and, where compatible, the wiring.

Fixtures

LED Temperature Derating

The manufacturer-specified reduction in an LED fixture's drive current or output at elevated ambient temperature, applied to keep the LED junction temperature within its rated limit.

Fixtures

LED Thermal Management

The overall design approach, combining heat sinking, thermal derating and enclosure design, used to keep an LED fixture's junction temperature within limits across its rated environmental range.

Fixtures

Lens Discoloration

Yellowing, clouding or fading of a fixture's optical lens caused by UV exposure, heat or contamination, which reduces transmitted light and can shift colour.

Fixtures

Level Check

A verification of installed elevation, level or slope against the applicable reference datum and tolerance.

Testing

Light Beam

The directional pattern in which a light fixture emits its luminous intensity, described by its beam axis (the aiming reference, usually close to the direction of peak intensity) and beam spread (the angular range over which intensity stays above a stated fraction of the peak). For airfield lights, the required beam shape and minimum intensities are given by the applicable isocandela diagram.

Photometry

Light Output

The optical output produced by a light source or fixture, which may be characterized by luminous flux, luminous intensity or another defined photometric quantity.

Fixtures

Light Output Degradation

The gradual fall in a fixture’s luminous output over its service life, for example from lamp or LED ageing and from dirt or discolouration on the optics. It is expressed as a reduction from the initial or rated intensity and is checked against the minimum intensity required for the light.

Photometry

Lighting Availability in LVP

Availability of required AGL functions during low-visibility operations, considering failed units, circuits, controls and redundancy.

Electrical

Lighting Guidance Command

Command sent to an AGL control system to establish a defined visual-guidance state.

Systems

Lighting System Availability

Proportion of required operating time during which the specified lighting function is capable of performing its intended service.

Systems

Lighting System Reliability

Probability or demonstrated ability of the lighting system to perform its required function for a specified operating period under defined conditions.

Systems

Lightning Protection

A coordinated system of measures intended to intercept, conduct and dissipate lightning current while limiting damage and hazardous potential differences.

Electrical

LIRLLow Intensity Runway Lights

Low Intensity Runway Lights (LIRL) provide low-intensity runway-edge guidance for runway operations where the approved lighting system uses the low-intensity class.

Fixtures

Load Calculation

The design calculation of a series circuit's total connected load, based on the number and VA rating of lamps and isolation transformers plus cable impedance, used to size a CCR and confirm it can drive the circuit within its rated capacity.

Testing

Load Test

A test performed with a defined electrical or mechanical load to verify equipment performance under representative operating conditions.

Testing

Load Verification

Confirmation that the connected AGL load matches the design/CCR capability and expected circuit loading.

Systems

Location Sign

Sign identifying the taxiway, runway or other movement-area location at which the sign is installed.

Signage

Lockout TagoutLockout / Tagout

A safety procedure in which an isolated circuit or piece of equipment is physically locked in the off position and tagged, preventing it from being re-energised while work is in progress.

Maintenance

Low Visibility Approach

Approach conducted under reduced visibility using the applicable approach lighting, runway lighting and instrument/operational procedures.

Operations

Low Visibility Inspection

Targeted inspection confirming the serviceability of critical visual aids, controls, power and monitoring before or during low-visibility operations.

Maintenance

Low Visibility Landing

Landing under reduced visibility using the applicable approach/runway visual aids, procedures and landing minima.

Operations

Low Visibility Operations

Low Visibility Operations are aerodrome operations conducted under defined reduced-visibility conditions that require specific procedures, minima, visual aids, surface-movement controls and system readiness measures.

Operations

Low Visibility ProceduresLVP

Operational procedures applied when visibility is reduced below defined conditions and additional controls, including enhanced visual aids, are required for safe aircraft and vehicle movement.

Operations

Low Visibility Takeoff

Takeoff operation conducted under reduced visibility with the applicable runway lighting, procedures and operational minima in force.

Operations

Low Visibility Taxiing

Taxi operation under reduced visibility requiring enhanced surface guidance, lighting conspicuity and movement control.

Operations

Lumen

SI unit of luminous flux; symbol lm.

Photometry

Luminance

Photometric quantity describing luminous intensity per unit projected area in a specified direction; unit cd/m².

Photometry

Luminous Flux

Photometric quantity representing the total luminous power evaluated according to the spectral luminous-efficiency function; unit lumen.

Photometry

Luminous Intensity

Photometric quantity describing luminous flux emitted by a source per unit solid angle in a specified direction.

Photometry

Lux

SI unit of illuminance; symbol lx. One lux equals one lumen per square metre.

Photometry

LVP Lighting Failure Response

Defined operational and maintenance response when a critical lighting function fails during low-visibility conditions.

Maintenance

LVP Lighting Test

Test confirming that the lighting functions required for an LVP configuration respond correctly to commands and faults.

Testing

LVP Maintenance Restriction

Maintenance limitation applied during low-visibility operations to prevent work from reducing required lighting availability or creating an unsafe condition.

Maintenance

M

Magnetic Heading

The direction in which an aircraft's nose is pointing, measured clockwise from magnetic north. Runway designators are derived from the runway's magnetic bearing, rounded to the nearest 10 degrees.

Operations

Main Supply

Normal electrical source feeding the AGL power-distribution system under ordinary operating conditions.

Electrical

Maintenance Log

A chronological record of maintenance activities performed on AGL equipment, including routine, preventive and corrective work.

Maintenance

Maintenance Safety Boundary

A defined physical or procedural boundary around a maintenance work site, restricting aircraft, vehicle or personnel access while work is in progress.

Maintenance

Mandatory Instruction Sign

Sign displaying a mandatory instruction, typically identifying a runway holding position or other location where a specified movement restriction applies.

Signage

ManholeCable Manhole

A below-grade access chamber, sized for personnel entry, installed along an underground duct route to house cable joints or equipment and to provide access for cable pulling, jointing, inspection and maintenance.

Electrical

Manoeuvring Area

The part of an aerodrome used for takeoff, landing and taxiing, excluding aprons.

Operations

MarshallingAircraft Marshalling

The use of visual hand or wand signals by a ground crew member to guide an aircraft during taxi, parking or pushback.

Operations

Material Test Certificate

A document issued by a material manufacturer certifying the chemical, mechanical or electrical properties of a specific batch of material.

Testing

Maximum IntensityMaximum Luminous Intensity

The highest luminous intensity value recorded within a fixture's photometric distribution, typically at or near the beam centre.

Photometry

Measurement Error

Difference between a measured quantity value and a reference/true quantity value as defined for the measurement context.

Testing

Measurement Geometry

Measurement Geometry is the defined spatial relationship among the measurement instrument, light source or test object, reference points, angles, distances and measurement surface used to obtain a valid measurement.

Testing

Measurement Plane

The defined surface or set of points, at a specified distance and orientation from a fixture, at which photometric readings are taken.

Testing

Measurement Point

A single defined location within a measurement plane or grid at which a photometric reading is recorded.

Testing

Measurement Uncertainty

Parameter characterizing the dispersion of values that could reasonably be attributed to the measured quantity.

Testing

Megger TestInsulation Resistance Test

A field term commonly used for an insulation-resistance measurement performed with a megohmmeter; the actual test voltage and method must follow the approved procedure.

Testing

MegohmmeterInsulation Resistance Tester

An electrical test instrument used to measure high resistance, particularly insulation resistance, by applying a specified DC test voltage.

Testing

Method Statement

A document describing the sequence, resources and safety controls for carrying out a specific work activity, prepared before the work begins.

Documentation

Minimum IntensityMinimum Luminous Intensity

The lowest acceptable luminous intensity value a fixture must produce at specified angles to remain compliant, below which the fixture is considered failed or due for replacement.

Photometry

MIRLMedium Intensity Runway Lights

Medium Intensity Runway Lights (MIRL) provide medium-intensity runway-edge guidance for the operating conditions and runway application for which the system is approved.

Fixtures

Modbus

Modbus is an industrial communication protocol used for exchanging data and control information between supervisory systems, controllers, instruments and other field devices using defined request-and-response data structures.

Systems

Mounting Stake

A ground anchor used to fix a portable or semi-permanent light fixture, such as a temporary runway or taxiway light, in position.

Fixtures

Movement Area

The part of an aerodrome used for aircraft takeoff, landing and taxiing, comprising the manoeuvring area and aprons.

Operations

Movement Area Map

Digital or graphical representation of runways, taxiways, aprons, holding positions and other controlled movement-area features.

Operations

Multilateration

Surveillance technique that estimates a transponder-equipped target position from differences in signal arrival times at multiple receiving stations.

Systems

MultimeterDigital Multimeter

A portable electrical measuring instrument capable of measuring selected quantities such as voltage, current and resistance.

Electrical

N

NCRNonconformance Report

The abbreviation commonly used on site and in documentation for a Nonconformance Report. See also: Nonconformance Report.

Documentation

NCR Closure

The formal process of verifying that the corrective action described in a Nonconformance Report has been completed and is effective, allowing the NCR to be closed.

Maintenance

Network Switch

A data-communications switch used within an ALCMS network to connect CCRs, field devices and control workstations over an Ethernet-based control and monitoring network.

Systems

Nonconformance Report

A formal document raised when work, material or a test result fails to meet a specified requirement, recording the deviation and the action taken. See also: NCR.

Testing

NOTAMNotice to Airmen / Notice to Air Missions as applicable

A notice distributed by telecommunication containing information on the establishment, condition or change of an aeronautical facility, service, procedure or hazard, timely knowledge of which is essential to personnel concerned with flight operations (ICAO Annex 15).

Documentation

O

Observation Angle

The angle, measured from a fixture's optical axis, at which a photometric measurement or visual assessment is taken.

Testing

Obstacle

Any fixed or mobile object, or part of one, located in an area intended for aircraft movement or projecting above a defined surface intended to protect aircraft in flight.

Operations

Obstacle Limitation Surface

A defined imaginary surface around a runway, establishing the maximum permitted height of objects to protect the safety of aircraft operations.

Operations

Obstruction Light

A light installed on an obstacle or structure to provide the required visual warning of the obstacle to aircraft.

Operations

Operational Readiness

The state in which an aerodrome facility, including its AGL system, is fully functional and available for use in operations.

Operations

Optical Axis

The central reference line of a fixture's optical system, around which the beam pattern is symmetric and from which aiming angles are measured.

Fixtures

Optical Contamination

Dirt, dust, moisture or residue on a lens or reflector that scatters or absorbs light, reducing a fixture's effective output.

Fixtures

Optical Lens

The transparent component of a fixture that shapes, directs or filters the light emitted from the source.

Fixtures

OutlierMeasurement Outlier

A measured value that falls significantly outside the expected range of a data set, flagged during data validation for re-measurement or investigation before being accepted or discarded.

Testing

P

PAPIPrecision Approach Path Indicator

Precision Approach Path Indicator (PAPI) system providing visual approach-slope guidance through the colour transition of its optical light units.

Fixtures

PAPI Aiming

Mechanical and optical adjustment of a PAPI unit to establish its specified vertical beam angle relative to the reference datum.

Fixtures

PAPI Alignment

Verification and adjustment of PAPI unit orientation, elevation, spacing and reference alignment against the approved siting design.

Fixtures

PAPI Approach Angle

The vertical glide-path angle, commonly 3.0 degrees, that a Precision Approach Path Indicator is set to indicate, matched to the runway's obstacle clearance surfaces and approach procedure design.

Fixtures

PAPI Cable Circuit

The electrical circuit, typically series-connected, linking a PAPI installation's individual light units to their power supply and control equipment.

Fixtures

PAPI Control Unit

The equipment that supplies power to and controls the operation of a PAPI installation's light units, and that can be coordinated with runway lighting intensity settings.

Fixtures

PAPI Frangible Support

The frangible mounting structure supporting a PAPI light unit, designed to break away under aircraft impact load to reduce hazard to the aircraft.

Fixtures

PAPI Glide Path

The visual approach slope defined by a PAPI's transition sector, in which a pilot on the correct path sees a set balance of red and white units (typically two of each), with a shift toward all-white indicating high and all-red indicating low.

Fixtures

PAPI Indication

The visual signal presented to a pilot by a PAPI installation, formed by the combination of red and white lights across its light units, indicating whether the aircraft is above, on, or below the glide path.

Fixtures

PAPI Light Unit

One of the individual light boxes in a PAPI (typically four) or APAPI (typically two) installation, each containing a light source and optical system that produces the red/white split used for glide-path indication. See also: PAPI Unit.

Fixtures

PAPI Operation in LVP

Operation of PAPI within the approved approach configuration during low visibility, including status, aiming and serviceability controls.

Fixtures

PAPI Optical System

The lens and light-source arrangement within a PAPI light unit that produces its precisely defined red-to-white color transition at the designed approach angle.

Fixtures

PAPI Photometric Check

A measurement of a PAPI light unit's beam intensity and, critically, the elevation angle at which its red/white color transition occurs, verifying it matches the promulgated approach angle.

Photometry

PAPI Power Supply

The electrical supply, typically fed from a dedicated series or constant-voltage circuit, that powers a PAPI installation's light units and control equipment.

Fixtures

PAPI Transition Sector

The narrow vertical angular band, centered on the designed approach angle, within which a PAPI light unit's indication changes from white to red.

Fixtures

PAPI UnitPAPI Light Unit

One optical light unit within a PAPI assembly that produces the required white/red indication according to its vertical aiming setting. See also: PAPI Light Unit.

Fixtures

PAPI Unit Alignment

The precise leveling and angular setting of a PAPI light unit, in elevation to set the correct transition angle and in azimuth to align with the extended runway centerline.

Fixtures

PAPI Unit Elevation

The vertical angle setting of an individual PAPI light unit, staggered slightly between the units so their combined indication produces the correct glide-path signal.

Fixtures

PAPI Unit Spacing

The lateral interval between adjacent PAPI light units in the wing bar. ICAO Annex 14 sets it at about 9 m (tolerance 1 m), with the units equally spaced.

Fixtures

Parallel Taxiway

A taxiway arranged substantially parallel to a runway to provide a route for aircraft movement between runway access points and other parts of the movement area.

Operations

Peak IntensityPeak Luminous Intensity

The single highest luminous intensity value recorded during a photometric scan, marking the point of maximum concentrated output within the beam.

Photometry

Permit to Work

A formal document authorising specific work to proceed, confirming that hazards have been identified and controls put in place.

Documentation

Phase SequencePhase Sequence Test

The order in which the phases of a three-phase electrical supply reach their respective phase positions, relevant to correct equipment rotation and connection.

Testing

Photometer

Instrument that measures a photometric quantity using a calibrated detector and associated signal-processing system.

Testing

Photometric Acceptance Band

Defined range within which a measured photometric result is considered acceptable.

Photometry

Photometric Acquisition Rate

Frequency at which the photometric system records measurement samples.

Photometry

Photometric Alignment Reference

Physical or survey reference used to establish the instrument/fixture orientation and measurement geometry.

Photometry

Photometric Angular Resolution

Smallest angular increment between photometric measurement directions in a scan or distribution.

Photometry

Photometric Calibration Factor

Factor used to convert an instrument response into the applicable photometric quantity based on calibration.

Photometry

Photometric Control Chart

Graphical statistical tool used to monitor a measurement or process over time against control limits.

Photometry

Photometric Dark Current

Detector output measured without the intended optical signal and used to correct the instrument baseline.

Photometry

Photometric Data Completeness

Degree to which all required measurement points, metadata and records have been captured without gaps.

Photometry

Photometric Data Integrity

Assurance that photometric data remain accurate, complete, traceable and unaltered through acquisition, processing and reporting.

Photometry

Photometric Detector Height

Vertical position of the photometric detector relative to the defined measurement datum.

Photometry

Photometric Distribution

The pattern of luminous intensity a fixture produces across a range of angles, typically presented as an isocandela diagram or table of values.

Photometry

Photometric Drift

Gradual change in instrument response or calibration factor with time, temperature, aging or use.

Photometry

Photometric Environmental Log

A record of field conditions during photometric measurement, such as ambient temperature, weather, background light level, pavement or lens contamination, and instrument alignment, used to contextualize results.

Photometry

Photometric Export File

Electronic file containing raw or processed photometric results transferred from the measurement system for analysis or reporting.

Photometry

Photometric Field Record

Field document capturing the installed fixture/sign identity, measurement conditions, observations and photometric results.

Photometry

Photometric Gain Check

Verification that detector/system response remains within the specified sensitivity or gain condition.

Photometry

Photometric GridPhotometric Measurement Grid

The array of measurement points, spaced at defined angular or linear intervals, used to map a fixture's photometric distribution during testing.

Photometry

Photometric Instrument Setup

Defined physical and software configuration of the photometric instrument before data acquisition.

Photometry

Photometric Linearity

Degree to which instrument response remains proportional to the applied photometric signal over the specified range.

Photometry

Photometric Maintenance

Upkeep activities such as cleaning, lamp or LED replacement and alignment correction, performed specifically to keep a fixture's measured light output within its required photometric limits.

Photometry

Photometric Measurement Distance

Defined distance between the photometric detector and the light source or measurement plane.

Photometry

Photometric Measurement Log

Record linking each photometric measurement to date, asset, instrument, operator, conditions and result.

Photometry

Photometric Pass/Fail Rule

Decision rule defining how measurement results, including uncertainty where applicable, are compared with acceptance limits.

Photometry

Photometric Processed Data

Measurement data after defined corrections, calculations, filtering, interpolation or conversion have been applied.

Photometry

Photometric Quality Control

Planned checks used to detect drift, abnormal measurements or process variation before results are released.

Photometry

Photometric Raw Data

Original unprocessed detector readings and associated measurement information captured during a photometric test.

Photometry

Photometric Reference Lamp

Calibrated lamp used as a photometric reference for checking or calibrating measurement equipment.

Photometry

Photometric Reference Standard

Calibrated reference used to compare or establish measurement performance with traceability to a recognized standard.

Photometry

Photometric Scan Rate

Rate at which the photometric system moves through or samples measurement directions during acquisition.

Photometry

Photometric Stability

Ability of the photometric measurement system to maintain consistent response over a defined period under controlled conditions.

Photometry

Photometric Test

A measurement of a fixture's luminous intensity, beam shape and/or colour, performed to verify its output meets the applicable specification.

Photometry

Photometric Test Report

A document recording the results of photometric measurements taken on a fixture or system, compared against the applicable acceptance criteria.

Photometry

Photometric Tolerance

Permitted deviation of a measured or controlled quantity from its specified target or limit.

Photometry

Photometric Uncertainty Budget

Structured evaluation listing the significant uncertainty contributions to a photometric measurement and their combination.

Photometry

Photometric Zero Offset

Instrument reading offset from the true zero condition before the intended photometric signal is applied.

Photometry

Photometry

Measurement of quantities referring to optical radiation as evaluated according to a defined spectral luminous-efficiency function.

Photometry

PLCProgrammable Logic Controller

Programmable Logic Controller used to execute control logic, process inputs/outputs and interface with field equipment in an automated control system.

Systems

Plug and Receptacle

The mating connector pair, typically L-823 style, used to join a fixture's pigtail cable to the circuit cable in a below-ground connection.

Fixtures

Power Analyzer

An instrument used to measure electrical parameters such as voltage, current, power, power factor, energy and waveform characteristics.

Electrical

Power Factor

The ratio of real power to apparent power for an AC electrical load, representing the phase/displacement and waveform relationship relevant to system loading.

Electrical

Power Loss

The difference between the power a CCR or circuit draws and the useful power delivered to the lamps, arising from transformer, conductor and regulator losses, and used in circuit efficiency and energy calculations.

Electrical

Power Quality

Characteristics of the electrical supply, including voltage, frequency, waveform distortion and transients, that affect AGL equipment operation.

Electrical

Power Supply Derating

Power supply derating is the reduction of the maximum allowable output or load capability of a power supply under specified temperature, installation, duty-cycle or other operating conditions so that thermal, electrical and reliability limits are not exceeded.

Electrical

PPEPersonal Protective Equipment

Equipment worn by personnel, such as high-visibility clothing, insulated gloves or safety footwear, to reduce exposure to identified hazards.

Operations

Pre-Commissioning Test

A test performed before operational commissioning to verify installation integrity, basic electrical/functional condition and readiness for final commissioning.

Testing

Preventive Maintenance

Maintenance carried out at planned intervals, regardless of current condition, to reduce the likelihood of failure.

Maintenance

Primary CablePrimary Series Circuit Cable

The cable carrying constant current from the CCR to the primary winding of each series-circuit isolating transformer.

Systems

Primary Connector

An FAA L-823 (or equivalent) watertight connector kit joining series-circuit primary cable to an isolation transformer's primary winding, rated up to about 5 kV with a low maximum contact voltage drop.

Fixtures

Prism

A precision-moulded glass or acrylic optical component that refracts light to shape a fixture's beam, commonly used in inset fixtures.

Fixtures

Prism Contamination

Dirt, moisture or corrosion affecting the internal prism of an inset or elevated fixture, which distorts or reduces the light exiting the fixture.

Fixtures

Product Datasheet

A manufacturer-issued document describing a product's technical specifications, ratings and performance characteristics.

Documentation

Proficiency Test

External comparison in which a laboratory or measurement provider demonstrates performance against an assigned or reference value.

Testing

Protective Device

Any device, such as a fuse, circuit breaker, RCD or surge arrestor, installed to automatically detect and interrupt a fault condition on an AGL circuit.

Electrical

Pushback Area

The apron area behind a parked aircraft used for pushback operations, kept clear of obstructions.

Operations

Q

Quality Assurance

The planned activities carried out to provide confidence that quality requirements will be met, focused on process rather than inspecting finished output.

Documentation

Quality Control

The activities used to verify that a specific product or piece of work meets its requirements, typically through inspection and testing of the output itself.

Testing

Quality Management System

The documented framework of policies, procedures and records an organisation uses to plan, control and improve the quality of its work.

Documentation

R

Random Error

Component of measurement error that varies unpredictably between repeated measurements.

Testing

Rapid Exit Taxiway

A taxiway designed and located to allow an aircraft landing on the runway to leave the runway at a higher speed than would normally be possible at a conventional taxiway exit.

Operations

Ratio TestTransformer Ratio Test

A test used to verify the transformation ratio of a transformer by comparing the measured primary-to-secondary relationship with the specified ratio.

Testing

RCLRunway Centerline Lights

Runway Centreline Lights (RCL) provide longitudinal visual guidance along the runway centreline for the applicable runway operation.

Fixtures

Reactance (X)

The imaginary component of electrical impedance, denoted X, arising from inductance or capacitance in series lighting circuits and affecting current flow alongside resistance.

Electrical

Redundancy for CAT III

Provision of alternate equipment, circuits, power paths or control functions intended to maintain required lighting capability after a single failure where the approved design requires it.

Electrical

Reference Axis

The fixed direction, established during design or commissioning, against which a fixture's actual aiming angle is measured and compared.

Testing

Reference Lamp

A lamp or light source with known, certified output characteristics, used to calibrate photometric test equipment or verify test setup accuracy.

Testing

Reference PointAerodrome Reference Point

The designated geographical coordinates identifying an aerodrome's location, published for navigation purposes.

Operations

Reflector

A component, typically a shaped mirrored surface, that redirects light from a source into the desired beam pattern.

Fixtures

REILRunway End Identifier Lights

Runway End Identifier Lights (REIL) provide rapid identification of the runway threshold by means of synchronized high-intensity flashing lights positioned near the runway threshold. See also: Runway End Identification Lights.

Fixtures

RELRunway Entrance Lights

Abbreviation for Runway Entrance Lights, the red in-pavement lights of the FAA Runway Status Lights (RWSL) system. See <a href="#term-runway-entrance-lights">Runway Entrance Lights</a>.

Operations

REL Activation Logic

Software/control rules that determine when Runway Entrance Lights illuminate or extinguish from surveillance-derived runway-status information.

Operations

Relay

An electrically operated switching device used to control or isolate circuits through a defined coil/control and contact arrangement.

Electrical

Reliability Run

Controlled operating period used to demonstrate stable AGL performance under representative conditions before final acceptance.

Testing

Remote Monitoring

Acquisition and display of equipment or system status at a location remote from the field equipment.

Systems

Remote Terminal Unit

A Remote Terminal Unit (RTU) is a field control and data-acquisition device that interfaces field inputs and outputs with a supervisory or control system and communicates operational data and commands over an approved communication network.

Systems

RepeatabilityMeasurement Repeatability

Repeatability is the closeness of agreement between repeated measurement results obtained under the same measurement conditions over a short period using the same method, instrument and operator where applicable.

Testing

Repeatability Study

Study of measurement agreement when the same method, instrument, operator and conditions are used over repeated measurements.

Testing

ReproducibilityMeasurement Reproducibility

The degree to which repeated measurements of the same quantity, taken under changed conditions such as a different operator, instrument or time, agree with one another.

Photometry

Reproducibility Study

Study of measurement agreement under changed conditions such as operators, instruments, locations or laboratories.

Testing

Residual Current

The current imbalance between line and neutral conductors, monitored by a residual current device to detect earth leakage and disconnect the circuit if it exceeds a safe threshold.

Electrical

Retest

Repeat test performed after correction, repair or clarification to demonstrate that the affected requirement is now satisfied.

Testing

Revision Control

The tracking of successive versions of a drawing or document, identified by revision letters or numbers, so changes can be traced and the current version identified.

Documentation

RFIRequest for Information

A formal query raised during design or construction to clarify a drawing, specification or requirement, along with the recorded response.

Documentation

Risk Assessment

A structured process of identifying hazards, evaluating the likelihood and severity of harm, and determining controls needed to reduce risk to an acceptable level.

Documentation

Risk Register

A document listing identified project or operational risks, their likelihood, impact and the controls or mitigations assigned to each.

Documentation

Root Cause Analysis

A structured investigation method used to identify the underlying cause of a nonconformance or failure, rather than stopping at its immediate symptom.

Maintenance

Route Conformance Monitoring

Function that compares actual surface movement against the assigned or expected route and detects deviations.

Systems

Routine Inspection

A scheduled, recurring inspection carried out at a fixed interval to confirm equipment remains in serviceable condition.

Maintenance

Routine Test

A test performed as standard practice on every unit or at every scheduled interval, as opposed to a special test carried out for a specific investigation.

Testing

Routing Guidance

Function that determines and communicates an approved taxi route between movement-area points.

Systems

Runway Centerline

The centre line of a runway, typically marked and, on precision runways, lit to guide an aircraft along the runway during landing, takeoff and roll-out.

Operations

Runway Centerline Light Alignment

The correct beam orientation of a runway centerline light fixture, aimed parallel to the runway centerline so it presents its designed intensity to an approaching or landing aircraft; verified during commissioning and periodic inspection.

Fixtures

Runway Centerline Light Color Transition

The change in runway centerline light color from white, to alternating red and white over the final 900 m of runway, to solid red over the final 300 m, providing the pilot a visual cue to remaining runway length.

Fixtures

Runway Centerline Light Spacing

The longitudinal interval between runway centreline lights: approximately 15 m on runways intended for operations in the lowest visibilities, and up to about 30 m otherwise, per ICAO Annex 14 and equivalent national criteria.

Fixtures

Runway Centerline Lighting in LVP

Use of runway centreline lights to provide longitudinal runway guidance during low-visibility operations.

Operations

Runway Closure

The temporary or permanent withdrawal of a runway from operational use, requiring notification and, where lighting is affected, appropriate switching or marking.

Operations

Runway Designation Sign

Sign displaying the runway designation associated with a runway holding or other aerodrome visual-aid location.

Signage

Runway Designator

A runway designator is the alphanumeric identifier assigned to a runway based primarily on its magnetic azimuth, expressed to the nearest 10 degrees, with additional identifiers used for parallel runways.

Operations

Runway Edge

The lateral boundary of the runway surface, typically marked and lit with runway edge lights.

Operations

Runway Edge Light Fixture Alignment

The correct aiming and leveling of a runway edge light fixture, ensuring its beam pattern is oriented as specified relative to the runway centerline and pavement surface.

Fixtures

Runway Edge Light Photometric Check

A field or bench measurement of a runway edge light fixture's luminous intensity, verifying it meets the minimum candela output required by its photometric classification.

Photometry

Runway Edge Light Spacing

The longitudinal interval between runway edge light fixtures, typically not exceeding 60 m, positioned in parallel rows along the full length of the runway.

Fixtures

Runway End

The physical extremity of the usable runway pavement. It may coincide with the threshold or be displaced from it, and it is marked at night by runway end lights (red, showing toward the runway).

Operations

Runway End Identification Lights

A pair of synchronized flashing white lights installed laterally at the runway threshold to give pilots rapid, positive identification of the runway end, particularly where the runway lacks other approach aids. See also: REIL.

Fixtures

Runway End Light Alignment

The correct positioning and aiming of the red runway end lights so they face along the runway and are visible to an aircraft on its landing roll or take-off run, as designed.

Fixtures

Runway Entrance Lights

Flush-mounted, in-pavement, unidirectional red lights (REL) arranged at runway/taxiway intersections to indicate that entering or crossing the runway is unsafe. In the FAA Runway Status Lights (RWSL) system, the REL subsystem uses surveillance inputs and activation logic to illuminate the lights at equipped intersections.

Operations

Runway Exit Sign

A sign near a runway exit identifying the taxiway designation of the exit ahead, helping a landing aircraft anticipate and take the correct turn-off.

Signage

Runway Guard Light

Yellow lights that flash alternately at a taxiway/runway intersection to increase the conspicuity of the runway holding position: either a pair on each side of the taxiway (Configuration A) or a row of in-pavement lights across the taxiway (Configuration B). See also: Taxiway Holding Position Light.

Fixtures

Runway Guard Light in LVP

Use of runway guard lights to increase conspicuity of a runway holding position during reduced visibility.

Operations

Runway Holding Position

Runway Holding Position is a designated position on a taxiway or other movement route where an aircraft or vehicle is required to hold before entering or crossing a runway or another protected area.

Operations

Runway Incursion

Runway Incursion is an occurrence involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and takeoff of aircraft.

Operations

Runway Incursion Hotspot

A location on the aerodrome identified, from historical data or layout analysis, as having a higher-than-average risk of runway incursion.

Operations

Runway Light Base Can

The below-grade housing into which a runway light fixture and its frangible coupling are mounted, providing a sealed, structurally anchored point for the cable and isolation transformer.

Fixtures

Runway Light Base Elevation

The vertical positioning of a runway light's base can and fixture relative to the pavement surface, set so the fixture presents its correct beam height without creating a foreign object hazard.

Fixtures

Runway Light Beam Orientation

The direction and angle at which a runway light fixture's optical beam is aimed, set during installation to meet the photometric coverage required for approaching or taxiing aircraft.

Fixtures

Runway Light Circuit Segmentation

The division of a runway lighting circuit into separately switchable or controllable sections, for example by runway third or light type, to allow selective control, maintenance isolation, or partial-runway operation.

Systems

Runway Light Connector Lead

The factory pigtail cable on a runway light fixture that terminates in an L-823-style plug, used to connect the fixture to its isolation transformer's secondary lead.

Fixtures

Runway Light Frangible Mount

A coupling supporting a runway light fixture that is designed to break away at a predetermined low load if struck by an aircraft, reducing hazard to the aircraft while the fixture separates cleanly from its base.

Fixtures

Runway Light Intensity Step

The brightness level, selected from the CCR's available steps, at which a runway lighting circuit is currently operating.

Systems

Runway Light Lens

The optical component of a runway light fixture that shapes and directs the light source's output into the required beam pattern and color.

Fixtures

Runway Light Maintenance Interval

The scheduled period between inspections, cleaning or photometric checks of runway light fixtures, set by the aerodrome's maintenance program to sustain required output and reliability.

Maintenance

Runway Light Optical Axis

The centerline of a runway light fixture's beam, around which its intensity distribution is measured and to which its aiming is referenced.

Fixtures

Runway Light Photometric Degradation

The gradual reduction in a runway light fixture's luminous output over time, due to lamp or LED aging, lens fouling, or optical component wear.

Photometry

Runway Light Prism

A refractive optical element, used in some fixture designs, particularly older incandescent fixtures, that redirects and shapes the light source's output into the required beam.

Fixtures

Runway Light Secondary Lead

The cable from an isolation transformer's secondary winding to the runway light fixture, carrying the supply for that fixture's lamp or LED driver, isolated from the primary series circuit.

Electrical

Runway Light Series Circuit Loading

The cumulative electrical load, from the number and type of fixtures and their isolation transformers connected to a single constant-current series circuit, kept within the CCR's rated capacity.

Electrical

Runway Light Service Life

The expected operational lifespan of a runway light fixture or its lamp/LED source before replacement is required, typically stated by the manufacturer under specified operating conditions.

Fixtures

Runway Shoulder

A prepared surface adjoining the runway edge, provided to support occasional excursions by aircraft and to resist erosion.

Operations

Runway Status Lights

Fully automated runway-safety lighting system that uses surveillance-derived traffic information and control logic to activate red in-pavement Runway Entrance Lights and Takeoff Hold Lights when runway entry, crossing or takeoff is unsafe.

Operations

Runway Strip

A defined area including the runway and any stopway, provided to reduce risk of damage to aircraft running off the runway and to protect aircraft flying over it during takeoff or landing.

Operations

Runway Threshold

The beginning of the portion of runway usable for landing, typically marked with threshold markings and lighting.

Operations

Runway Threshold Identification

The set of lighting and marking used to positively identify the beginning of the usable runway to a pilot, principally the green threshold lights and threshold pavement markings.

Operations

Runway Threshold Light Alignment

The correct aiming of the green threshold lights across the runway end, ensuring their beam is oriented to be visible to an aircraft on final approach.

Fixtures

Runway Threshold Wing Bar

A row of additional green lights on each side of the runway at the threshold, extending outward at right angles to the runway edge lights (ICAO: at least five lights over at least 10 m), to make the threshold more conspicuous, particularly on precision approach runways.

Fixtures

Runway Touchdown Zone Light

One of the white lights, normally in barrettes of at least three lights, installed in symmetrical pairs on either side of the runway centreline in the touchdown zone of a precision approach runway to give distance and alignment guidance.

Fixtures

Runway Turn Pad

A defined area on a runway, adjacent to the end, provided to allow an aircraft to make a 180-degree turn.

Operations

Runway Visual Range

Runway Visual Range (RVR) is the meteorological/operational measure of the horizontal distance over which a pilot on the runway centreline can see runway markings or lights used for approach and runway operations.

Operations

RVR Operating Condition

Defined runway visual range condition used to determine which low-visibility operating procedures and lighting configurations apply.

Documentation

RVR Sensor Interface

Data/control interface through which an RVR measurement system supplies visibility information to an airport operational or control system.

Systems

RWSLRunway Status Lights

Runway Status Lights (RWSL) is a fully automated runway-safety lighting system that uses surveillance-derived traffic information and control logic to activate red in-pavement Runway Entrance Lights and Takeoff Hold Lights when runway entry, crossing or takeoff is unsafe.

Operations

RWSL Controller

Control processor that receives surveillance information, executes RWSL logic and commands REL/THL field lighting.

Systems

RWSL Event Log

A time-stamped record of Runway Status Light system activity, including REL/THL light commands, target detections, mode changes, alarms and faults, used for operational review and troubleshooting.

Documentation

S

Safety Cone

A portable cone used to mark hazards, work areas or restricted zones on the airside.

Operations

Salt Spray Test

An accelerated corrosion test in which a component is exposed to a salt fog environment to assess its resistance to corrosion, relevant for coastal or humid-climate installations.

Testing

Sampling Plan

A defined method for selecting a subset of items from a batch for inspection or testing, used when testing every item is impractical.

Testing

SATSite Acceptance Test

The abbreviation for Site Acceptance Test, commonly used in contract documents and test procedures. See also: Site Acceptance Test.

Testing

SCADASupervisory Control and Data Acquisition

Supervisory Control and Data Acquisition system used to supervise, monitor, alarm and record distributed equipment and process information.

Systems

SCADA Alarm

An alert generated within the supervisory control and data acquisition layer of an ALCMS when a monitored AGL parameter, such as current, voltage or fault status, falls outside its defined limit.

Systems

Schematic Diagram

A simplified drawing showing the electrical connections and logic of a circuit or system without representing physical layout.

Documentation

Secondary AGL Cable

Secondary AGL Cable is the cable connecting the secondary winding of an isolating transformer to the associated AGL light fixture or load. See also: Secondary Cable.

Electrical

Secondary CableSecondary Fixture Cable

The short length of cable connecting an isolating transformer's secondary winding to the fixture itself. See also: Secondary AGL Cable.

Electrical

Secondary Connector

An FAA L-823 (or equivalent) quick-disconnect plug-and-socket joining an isolation transformer's secondary lead to a fixture's plug lead, rated for submersible outdoor service with a low maximum contact voltage drop.

Fixtures

Selective Coordination

Protection arrangement in which the protective device nearest a fault operates before upstream devices, where the design requires selectivity.

Electrical

Selector Switch

A manually operated switch used to select among defined control modes, sources, intensity steps or operating states.

Electrical

Series Circuit

An AGL series circuit is a closed-loop lighting power circuit in which individual light loads are connected in series and supplied from a constant-current regulator.

Systems

Series Circuit Continuity

The unbroken electrical path through every lamp and isolation transformer wired in series on an AGL circuit; the CCR relies on this continuity to maintain its regulated current, and a break registers as an open-circuit fault.

Electrical

Series Circuit Current

The single current value common to every fixture connected in a series AGL circuit, set by the CCR and unaffected by the number of fixtures.

Systems

Series Circuit Isolation

Electrical separation within the AGL series-circuit architecture that limits direct electrical connection between circuit sections or equipment as required by the design.

Electrical

Series Circuit Power Factor

The ratio of real to apparent power drawn by a series airfield lighting circuit, governed mainly by the reactive (magnetizing) current of the isolation transformers and the CCR's own regulating transformer.

Electrical

Series Circuit Resistance

The total electrical resistance of a series AGL circuit, comprising cable, connector and transformer resistance, measured to detect degradation or faults.

Electrical

Shallow Base

A base can with reduced burial depth, used where ground conditions or ducting depth limit installation depth.

Fixtures

Shop Drawing

A detailed fabrication or installation drawing prepared by a contractor or supplier, submitted for approval before manufacture or construction.

Documentation

Short-Circuit Level

Available short-circuit current or fault level at a defined point in the electrical system.

Electrical

Sign Access Panel

Removable panel providing access to specified internal electrical or optical components.

Signage

Sign Base

Structural support/base connecting the sign assembly to its foundation or mounting system.

Signage

Sign Brightness

Controlled visual output level of an illuminated sign, normally adjusted to maintain adequate conspicuity for operating conditions.

Signage

Sign Cable Entry

Sealed point where the sign power/control cable enters the housing or base.

Signage

Sign Chromaticity

Quantitative specification of the sign's emitted or reflected color using an applicable chromaticity system.

Photometry

Sign Circuit Isolation

Electrical separation of the sign from its supply/circuit for safe maintenance or fault isolation.

Signage

Sign Cleaning

Removal of dirt, dust, deposits or other contamination from sign optical surfaces to restore intended visibility and photometric performance.

Signage

Sign Connector

Electrical connector used to connect the sign to its supply or internal wiring while maintaining the required electrical and environmental performance.

Signage

Sign Contrast

Difference in luminance or visual appearance between the sign legend and its background that supports legibility.

Signage

Sign Door

Access door or removable panel providing maintenance access to internal sign components.

Signage

Sign Drainage

Provision for removing accumulated water from the sign housing or base assembly.

Signage

Sign External Illumination

Illumination applied to the sign from an external light source rather than an internal optical system.

Signage

Sign Face

Front visual surface of an airfield sign carrying the legend, color and optical elements visible to the intended observer.

Signage

Sign Foundation

Civil/structural foundation transferring sign loads to the ground while maintaining required position and stability.

Signage

Sign Framing

Structural members that support the sign panel and maintain dimensional rigidity.

Signage

Sign Frangible Support

Support designed to meet the applicable frangibility requirement for an aerodrome visual-aid sign installation.

Signage

Sign Functional Test

Test confirming correct sign legend illumination, brightness control, electrical operation and relevant monitoring functions.

Signage

Sign Housing

Enclosure that protects the sign optical, electrical and structural components from environmental exposure.

Signage

Sign Internal Illumination

Illumination produced within the sign housing to light the legend or sign face.

Signage

Sign LED Module

LED light source/module used to provide the required internal illumination of an illuminated sign.

Signage

Sign Legend

Letters, numbers, symbols or combinations displayed on the sign face to convey the required aerodrome information.

Signage

Sign Legend Height

Specified character height of the sign legend, selected to provide required readability from the intended viewing distance.

Signage

Sign Legend Stroke

Specified width of the strokes forming letters, numerals or symbols in the sign legend.

Signage

Sign LGP

Light-guide plate used in an edge-lit sign to distribute LED light across the sign face.

Signage

Sign Maintenance

Planned and corrective activities used to preserve sign structure, optics, illumination, electrical connections and legibility.

Signage

Sign Module Replacement

Controlled replacement of a failed or degraded illuminated sign module while maintaining the approved optical and electrical configuration.

Signage

Sign Panel

Structural/visual panel forming the main body of an airfield sign and supporting the legend and optical system.

Signage

Sign Sealing

Sealing arrangement that limits water and contaminant ingress into the sign housing and electrical compartments.

Signage

Sign Transformer

Isolation transformer or other specified power component used to supply an illuminated airfield sign circuit.

Signage

Sign Uniformity

Degree to which the required illuminated sign area maintains consistent luminance without unacceptable bright/dark regions.

Signage

Signal Light

An aerodrome visual aid capable of transmitting defined light signals to aircraft when the applicable operational system requires them.

Operations

Single Line Diagram

A simplified drawing representing a three-phase electrical system using a single line, showing major equipment, protective devices and circuit connections.

Documentation

Site Acceptance Test

A controlled test performed after site installation to verify the installed equipment/system against the approved site acceptance criteria. See also: SAT.

Testing

SMGCSSurface Movement Guidance and Control System

Surface Movement Guidance and Control System (SMGCS) is the set of procedures, facilities, equipment and operational arrangements used to support the safe movement of aircraft and vehicles on the aerodrome surface, particularly under reduced-visibility or complex operating conditions.

Documentation

SMGCS RouteSurface Movement Guidance Route

A defined route, part of a Surface Movement Guidance and Control System, established for aircraft or vehicle movement during low-visibility conditions.

Systems

SMR Surface Movement Radar

Surface radar used to detect and track aircraft and vehicles on or near the movement area.

Operations

Solid Angle

A three-dimensional angular measure, expressed in steradians, describing the extent of a beam or field of view from a point source, used in luminous flux and intensity calculations.

Photometry

Special Test

A test carried out outside the routine schedule, typically to investigate a specific fault, verify a repair, or satisfy a particular contractual requirement.

Testing

Spectral Power Distribution

Distribution of optical power of a light source as a function of wavelength.

Photometry

Stand Lead-In Line

A marking, sometimes accompanied by lighting, guiding an aircraft into its parking stand.

Signage

Stand Lead-Out Line

A marking guiding an aircraft out of its parking stand toward the taxiway system.

Signage

Stop Bar Clearance

The air traffic control authorization required before an aircraft or vehicle may cross an illuminated stop bar; the stop bar lighting itself is a visual indication and does not substitute for the controller's instruction.

Operations

Stop Bar Control

The switching function, typically via CCR or ALCMS, that illuminates or extinguishes a stop bar to indicate whether an aircraft or vehicle is cleared to cross a runway-holding position.

Systems

Stop Bar Interlocking

A control logic that prevents a stop bar and the taxiway centreline lights beyond it from being illuminated at the same time, so a crossing is never shown as both stopped and cleared.

Operations

Stop Bar Light

A red, controlled lighting element installed at a holding position to indicate that movement beyond the stop bar is not permitted when the stop bar is illuminated.

Fixtures

Stop Bar Operation in LVP

Controlled use of stop bars during low visibility to provide positive visual control of movement across protected taxiway/runway holding positions.

Operations

Stop Bar Status in A-SMGCS

Status information indicating whether a stop bar is illuminated, extinguished, unavailable or otherwise reported by the lighting-control interface.

Systems

SubmittalTechnical Submittal

A document, drawing or sample provided by a contractor to the engineer or client for review and approval before proceeding with the related work.

Documentation

Surface Movement

The movement of aircraft and vehicles on the ground area of an aerodrome, monitored and controlled to maintain safety.

Operations

Surface Movement Control

Control function that authorizes, sequences or restricts aircraft and vehicle movement on the aerodrome surface.

Operations

Surface Movement Guidance

Information, visual aids, systems or procedures that guide aircraft and vehicles along approved movement-area routes.

Documentation

Surface Movement Sensor

Sensor system providing aircraft/vehicle position or movement information for surface surveillance.

Operations

Surge Arrester

A device that limits transient overvoltage and diverts surge current to a suitable discharge path to protect connected electrical equipment.

Electrical

Surge Protection

Devices installed to limit transient overvoltages, such as those from lightning or switching, from damaging AGL equipment.

Electrical

Surge Protective DeviceSPD

A Surge Protective Device (SPD) is a protective device that limits transient overvoltage and diverts or clamps surge current away from connected electrical equipment to reduce damage caused by lightning-induced or switching transients. Also commonly called a surge protection device.

Electrical

Surveillance Function

A-SMGCS function that determines the position and movement of aircraft and vehicles using the adopted surveillance sources.

Systems

Systematic Error

Component of measurement error that remains constant or changes predictably under repeated conditions.

Testing

T

Takeoff Hold Lights

In-pavement, unidirectional red lights arranged in longitudinal rows near the runway centreline that indicate to a departing aircraft that takeoff is unsafe because conflicting traffic occupies or is about to occupy the runway.

Operations

Taxi Route Display

Display of the approved or assigned taxi route for use by an operator or controller.

Systems

Taxiway Centerline

The centre line of a taxiway, along which taxiway centreline lights or markings are positioned to guide aircraft.

Operations

Taxiway Centerline Guidance

The visual path formed by taxiway centreline lights that a pilot follows to keep the aircraft on the taxiway centreline during taxi.

Operations

Taxiway Centerline Guidance in A-SMGCS

Integration of taxiway centreline lighting or related guidance with the surface-movement guidance function.

Systems

Taxiway Centerline Light

An in-pavement or otherwise approved taxiway lighting element used to provide longitudinal centreline guidance along a taxi route.

Fixtures

Taxiway Centerline Light Alignment

The correct physical positioning and levelling of a centreline fixture so its beam is oriented along the taxiway centreline as designed.

Fixtures

Taxiway Centerline Light Color

The specified colour of taxiway centreline lights: green, except along a runway exit taxiway, where ICAO calls for alternating green and yellow from the runway centreline out to the edge of the ILS/MLS critical/sensitive area (or the inner transitional surface, whichever is farther), then green.

Fixtures

Taxiway Centerline Light Spacing

The maximum distance permitted between successive taxiway centreline fixtures, set by the applicable standard to maintain continuous visual guidance.

Fixtures

Taxiway Centerline Lighting in LVP

Use of taxiway centreline lights to provide continuous or controlled routing guidance when surface visibility limits ordinary visual navigation.

Operations

Taxiway Clearance Bar

A row of yellow lights installed across a taxiway at an intersection to indicate the holding position for aircraft awaiting clearance.

Fixtures

Taxiway Closure

The temporary or permanent withdrawal of a taxiway from operational use.

Operations

Taxiway Curve Lighting

Reduced-spacing taxiway centreline or edge lighting installed through a curve to give pilots earlier and clearer indication of the turn.

Operations

Taxiway Designation Sign

A yellow-on-black location sign displaying a taxiway's alphanumeric designator, mounted at intersections to confirm which taxiway an aircraft is currently on.

Signage

Taxiway Designator

The alphanumeric identifier assigned to a taxiway, used in markings, signage and radio communication.

Signage

Taxiway Edge

The lateral boundary of a taxiway's usable surface, marked and often delineated with taxiway edge lights.

Operations

Taxiway Edge Delineation

The marking of the physical edges of a taxiway using edge lights or reflective markers so pilots and vehicle operators can identify the usable pavement width.

Signage

Taxiway Edge Light

A light fixture used to define the lateral limits of a taxiway and provide visual guidance for aircraft ground movement.

Fixtures

Taxiway Edge Light Alignment

The correct physical positioning of taxiway edge fixtures relative to the pavement edge, per the design layout.

Fixtures

Taxiway Edge Light Color

The specified colour, typically blue, that a taxiway edge fixture must emit.

Fixtures

Taxiway Edge Light Spacing

The maximum distance permitted between successive taxiway edge fixtures.

Fixtures

Taxiway Guidance in LVP

Integrated visual and procedural guidance used to keep aircraft/vehicles on approved taxi routes during low visibility.

Operations

Taxiway Holding Position

A designated position intended to protect a runway, obstacle limitation surface, or ILS critical or sensitive area, at which taxiing aircraft and vehicles must stop unless authorised.

Operations

Taxiway Holding Position Light

A yellow light installed at a runway holding position to show pilots and vehicle drivers where they must stop. The usual form is the runway guard light. See also: Runway Guard Light.

Fixtures

Taxiway Intersection

The point where two or more taxiways, or a taxiway and runway, meet.

Operations

Taxiway Intersection Lighting

Additional or modified lighting installed at a taxiway intersection to clearly indicate the junction and guide the correct turn.

Operations

Taxiway Lead-Off Lighting

Lighting that guides an aircraft from the runway onto a connecting taxiway after landing.

Operations

Taxiway Lead-On Lighting

Lighting that guides an aircraft from a taxiway onto the runway before takeoff.

Operations

Taxiway Light Base

The below-ground housing, deep or shallow base, into which a taxiway fixture is mounted and through which its cable is connected.

Fixtures

Taxiway Light Fixture Elevation

The height a taxiway light fixture protrudes above the pavement surface, controlled to remain within tolerances that avoid aircraft or vehicle strike risk.

Fixtures

Taxiway Light Prism Condition

The physical state, clean, cracked or discoloured, of the internal prism of a taxiway inset fixture, assessed during inspection.

Maintenance

Taxiway Light Transformer

The isolation transformer connected to an individual taxiway fixture in a series circuit. It passes the regulated series current to the fixture's secondary circuit while keeping the fixture electrically isolated, so a failed lamp does not open the whole series loop.

Electrical

Taxiway Lighting Circuit

A series or parallel electrical circuit dedicated to powering a defined group of taxiway lighting fixtures.

Fixtures

Taxiway Lighting Commissioning

The testing and verification process performed before a newly installed or modified taxiway lighting circuit is brought into operational service.

Testing

Taxiway Lighting Failure

The loss of function of one or more taxiway lighting fixtures or a circuit, requiring reporting and corrective action.

Maintenance

Taxiway Lighting Inspection

A scheduled visual or functional check of taxiway lighting fixtures and circuits to confirm serviceability.

Maintenance

Taxiway Lighting Intensity

The luminous intensity setting, or brightness step, applied to a taxiway lighting circuit, adjustable via the CCR to suit visibility conditions.

Systems

Taxiway Lighting Maintenance

Routine and corrective work performed to keep taxiway lighting fixtures and circuits within their required performance limits.

Maintenance

Taxiway Routing Status

Current state of a taxi route, including active, blocked, unavailable or otherwise constrained segments.

Systems

Taxiway Shoulder

A prepared surface adjoining the taxiway edge, provided to resist erosion and support occasional aircraft excursions.

Operations

Taxiway Stop Bar

A set of unidirectional red lights installed across a taxiway at a runway-holding position to indicate that crossing is not authorised.

Operations

Taxiway Straight Section

A length of taxiway centreline or edge lighting installed on a straight run, where spacing follows the standard interval rather than the reduced curve spacing.

Fixtures

TDZLTouchdown Zone Lights

Touchdown Zone Lights providing visual reference to the runway touchdown zone during landing.

Fixtures

Technical Data Sheet

A document specifying the technical parameters, tolerances and test values applicable to a particular material, component or installation.

Documentation

Technical Query

A question raised by site or design personnel seeking clarification on a technical point, tracked until formally answered and closed.

Documentation

Temperature Rise Test

A test measuring the temperature increase of a component such as a transformer or CCR under rated load, to confirm it stays within its thermal design limits.

Testing

Temperature Test

A controlled measurement or test used to verify equipment temperature or temperature-related performance under the defined condition.

Testing

Test Certificate

A signed document recording the results of a specific test, confirming pass/fail status, used as formal evidence for acceptance or handover.

Testing

Test Data Sheet

Controlled form for recording measured values, test conditions, instrument identification and acceptance results.

Testing

Test Deviation

Documented departure from the approved test method or acceptance requirement, including technical justification and approval where permitted.

Testing

Test Exemption

Formally approved exclusion from a specified test requirement when the governing procedure allows such an exemption.

Testing

Test Instrument Register

Controlled list of instruments used for testing, including identification, range, calibration status and ownership.

Testing

Test Method Statement

Approved document describing how a specific AGL test will be performed, including equipment, sequence, safety controls and acceptance criteria.

Testing

Test Procedure

Controlled sequence of steps for performing a defined AGL inspection or measurement consistently.

Testing

Test Report

A document recording the procedure, results and pass/fail outcome of a test performed on AGL equipment or a circuit.

Testing

Test Witness

A person, often the client's representative or the certifying authority, present to observe and confirm a test was performed correctly and its results are valid.

Testing

Thermal Derating

The planned reduction in a component's rated output or current-carrying capacity as ambient or operating temperature rises, applied to avoid overheating.

Electrical

THLTakeoff Hold Lights

Takeoff Hold Lights used within the FAA Runway Status Lights system to provide a red warning to an aircraft when takeoff is unsafe or should not be initiated.

Operations

THL System

Takeoff Hold Lights subsystem of RWSL that uses traffic information and control logic to indicate an unsafe takeoff condition.

Systems

Threshold Crossing Height

The height of the glide path above the runway threshold. For visual slope indicators such as PAPI it is set so the aircraft's wheels clear the threshold by an adequate margin (minimum eye height over the threshold).

Operations

Time Domain Reflectometry

Time Domain Reflectometry (TDR) is a cable diagnostic and fault-location technique that transmits a controlled electrical pulse or signal into a cable and analyzes reflected energy caused by impedance discontinuities to estimate the location and nature of a fault.

Electrical

Toolbox Talk

A short, informal briefing given to a work team before starting a task, covering the specific hazards and controls relevant to that day's work.

Operations

Torque TestTorque Verification Test

A verification of applied fastener torque using a suitable calibrated torque tool against the specified installation torque.

Testing

Touchdown Zone

The portion of a runway, beyond the threshold, where landing aeroplanes are intended first to contact the runway (ICAO). FAA practice treats the first 3,000 ft (about 900 m) from the threshold as the touchdown zone. On precision approach runways it is marked by touchdown zone markings and lit by touchdown zone lights.

Operations

Touchdown Zone Light Spacing

The longitudinal and lateral arrangement of touchdown zone light barrettes: pairs symmetric about the runway centreline, spaced 30 m or 60 m apart longitudinally, extending up to 900 m from the threshold (less on short runways), per ICAO Annex 14 and equivalent FAA criteria.

Fixtures

TraceabilityMeasurement Traceability

Property of a measurement result that can be related to a stated reference through an unbroken documented chain of calibrations, each contributing to measurement uncertainty.

Testing

Transformer Acceptance Criteria

Defined limits and conditions used to determine whether a transformer is acceptable for the intended application.

Testing

Transformer Ambient Temperature

Temperature of the surrounding environment used when evaluating transformer thermal performance and rating.

Electrical

Transformer Batch Test

Test applied to a defined production batch according to the applicable quality-control or specification requirements.

Testing

Transformer Connector Polarity

Defined relationship of connector contacts/leads that must be maintained for correct circuit connection.

Electrical

Transformer Copper Loss

Winding I²R loss produced by current flowing through transformer winding resistance.

Electrical

Transformer Core

The laminated magnetic material, typically silicon steel, around which a series isolation transformer's windings are wound, providing the flux path that couples current between primary and secondary.

Electrical

Transformer Core Loss

Power loss in the transformer magnetic core caused primarily by hysteresis and eddy-current effects.

Electrical

Transformer Dielectric Strength

Ability of the transformer insulation system to withstand a specified electrical stress without breakdown.

Electrical

Transformer Encapsulation

Surrounding a component or winding assembly with an insulating material to provide electrical and environmental protection.

Electrical

Transformer Enclosure

Physical housing or construction protecting the transformer from mechanical and environmental exposure.

Electrical

Transformer Frequency

Rated AC supply frequency for which the transformer is designed to operate within its specified performance.

Electrical

Transformer Impulse Withstand

Ability of the transformer insulation system to withstand specified transient impulse voltage.

Electrical

Transformer Insulation

The dielectric materials and encapsulation, such as cast epoxy or a synthetic rubber compound, that separate a series isolation transformer's windings from each other, from the core, and from earth, rated for the circuit voltage and for buried or wet-location service.

Electrical

Transformer Insulation Class

Thermal/electrical insulation classification of the transformer winding system according to the applicable specification.

Electrical

Transformer Lead Identification

Marking used to distinguish transformer leads and maintain correct circuit connection.

Electrical

Transformer Lead Length

Specified physical length of the transformer connection lead between the transformer body and termination/connector.

Electrical

Transformer Leakage Reactance

The reactance representing magnetic flux that links only one winding of a transformer rather than both, which limits fault current and contributes to voltage drop under load.

Electrical

Transformer Load Voltage

Secondary voltage measured while the transformer supplies its specified connected load.

Electrical

Transformer Mechanical Integrity

Condition of the transformer body, leads, seals, terminals and construction against physical damage or loosening.

Electrical

Transformer Moisture Resistance

Ability of the transformer construction and insulation system to resist performance degradation from moisture exposure.

Electrical

Transformer No-Load Voltage

Secondary voltage measured with the specified primary applied and no external secondary load connected.

Electrical

Transformer Overload

Operation beyond the transformer's specified current or VA capability.

Electrical

Transformer Potting

Process of filling an electrical assembly with insulating compound to improve environmental protection and mechanical support.

Electrical

Transformer Power Factor

The ratio of real to apparent power at a series isolation transformer's primary, determined mainly by its magnetizing (reactive) current.

Electrical

Transformer Primary

The winding of a series isolation transformer that is connected directly into the constant-current series circuit and carries the CCR's regulated current.

Electrical

Transformer Primary Voltage

The voltage across a series isolation transformer's primary winding while it carries the circuit current. Because the primary is fed with constant current (for example 6.6 A), this voltage is not a fixed rating; it depends on the connected load. The transformer is rated by primary current and VA.

Electrical

Transformer Rated Current

Maximum or nominal current for which the transformer is designed under its specified operating conditions.

Electrical

Transformer Rated VA

Apparent-power rating of the transformer based on its specified current and voltage/load conditions.

Electrical

Transformer Rating

A series isolation transformer's specified primary current, secondary VA capacity and voltage class, selected to match the CCR output and the connected lamp per AC 150/5345-47.

Electrical

Transformer Regulation

Change in secondary voltage between defined no-load and load conditions, expressed according to the applicable transformer definition.

Electrical

Transformer Replacement

The removal and replacement of a failed or out-of-tolerance isolating transformer in a series circuit.

Electrical

Transformer Routine Test

Production test performed on each transformer or defined production unit to verify specified characteristics.

Testing

Transformer Secondary

Transformer Secondary is the winding or output side of an isolating transformer that supplies the connected AGL fixture or secondary circuit while remaining electrically isolated from the primary series-circuit side.

Electrical

Transformer Secondary Load

Electrical load connected to the transformer secondary, normally the AGL fixture or designated load.

Electrical

Transformer Secondary Voltage

Voltage appearing at the transformer secondary under the defined load and operating condition.

Electrical

Transformer Serial Number

Unique identifier assigned to an individual transformer for traceability.

Electrical

Transformer Short-Circuit Withstand

Ability of the transformer to withstand specified short-circuit stresses without unacceptable damage.

Electrical

Transformer Total Loss

The sum of a transformer's no-load (core/iron) loss and load (copper/I²R) loss under its defined operating condition, representing total power dissipated as heat.

Electrical

Transformer Turns Ratio

Ratio of primary to secondary winding turns, which sets the relationship between primary and secondary current and voltage. Many series isolation transformers are 1:1 (6.6 A / 6.6 A); others, such as 20 A / 6.6 A types, step the current down.

Electrical

Transformer Type Test

Design-verification test performed on a representative transformer type to demonstrate compliance with specified requirements.

Testing

Transformer Voltage Drop

Difference between a defined transformer/input voltage and the corresponding loaded output voltage.

Electrical

Transformer Winding

A coil of insulated conductor, primary or secondary, wound around a series isolation transformer's core to transfer power between the constant-current circuit and the lamp by mutual induction while maintaining electrical isolation.

Electrical

Transformer Winding Resistance

Electrical resistance of a transformer winding, used for loss, temperature and condition assessment.

Electrical

Transient Overvoltage

Short-duration overvoltage caused by switching, lightning or other transient events.

Electrical

Trend Data

Historical measurement or performance data plotted over time to identify gradual changes, such as declining fixture intensity or rising cable resistance.

Testing

True Bearing

A direction measured relative to true, geographic north, as distinct from magnetic heading, used in some navigation and survey contexts.

Operations

Type A Uncertainty

Measurement uncertainty evaluated by statistical analysis of repeated observations.

Testing

Type B Uncertainty

Measurement uncertainty evaluated from sources other than repeated statistical observations, such as calibration certificates, specifications or prior data.

Testing

Type Test

A test performed once on a representative sample of a product design, to demonstrate the design itself meets a standard, as distinct from testing every individual unit produced.

Testing

U

UniformityPhotometric Uniformity

A measure of how evenly light intensity is distributed across a runway, taxiway or fixture's beam, usually expressed as a ratio between minimum and maximum or minimum and average values.

Photometry

UV ResistanceUltraviolet Resistance

A material's ability to withstand degradation such as cracking, discoloration or loss of strength from prolonged ultraviolet exposure, relevant to outdoor AGL cable jackets, lenses and housings.

Electrical

V

VASIVisual Approach Slope Indicator

Visual Approach Slope Indicator providing visual glide-path information to an approaching aircraft.

Fixtures

VASISVisual Approach Slope Indicator System

Visual Approach Slope Indicator System providing visual glide-path guidance through light indications viewed from the approach.

Fixtures

Vehicle Access Control

The system of permits, escorts and physical controls governing which vehicles may enter the airside movement area and under what conditions.

Documentation

Vehicle Tracking

Continuous or periodic determination of a vehicle's identity and movement position on the aerodrome surface.

Operations

Vibration Test

A test in which a component is subjected to controlled vibration to verify it withstands the mechanical stresses of transport, jet blast or ground operation without failure.

Testing

Viewing Angle

The angle, relative to a fixture's optical axis, from which an observer sees the light, used to define the angular range over which a signal must remain visible.

Fixtures

Visual Docking Guidance System

A system that provides visual guidance and stopping information to assist an aircraft in reaching its designated parking position.

Operations

Visual Guidance

The general term for information conveyed to pilots and vehicle drivers through lights, markings and signs to support safe ground movement and approach and landing.

Operations

Visual Inspection

A systematic examination of physical condition, identification, installation, cleanliness, damage, alignment and other observable characteristics.

Maintenance

Voltage Calculation

Voltage calculation is the determination of expected electrical voltage, voltage drop or circuit voltage from the source voltage, load, conductor characteristics, resistance or impedance and the applicable circuit configuration.

Electrical

Voltage Disturbance

Temporary or transient deviation of supply voltage from its nominal condition.

Electrical

Voltage Drop

The reduction in voltage along a conductor or circuit caused by its impedance and the current flowing through it.

Electrical

Voltage Measurement

The recording of actual voltage present at a defined point in an AGL circuit, taken to verify it matches design or rated values.

Testing

Voltage Sag

A short-duration reduction in RMS supply voltage. Its effect on AGL equipment depends on the duration, magnitude, source and equipment characteristics and should be evaluated against the applicable power-quality requirements.

Electrical

Voltage Swell

A short-duration increase in RMS supply voltage. Its effect on AGL equipment depends on the duration, magnitude, source and equipment characteristics and should be evaluated against the applicable power-quality requirements.

Electrical

W

Warning Light

A light, of a distinct colour or flash pattern, used to indicate a hazard, fault or restricted condition rather than to provide navigational guidance.

Operations

Warning Tape

Buried identification tape placed above an underground cable/duct route to warn future excavation personnel.

Electrical

Waterproof Connector

A connector, typically an L-823 style, designed and sealed to prevent water ingress at below-ground or exposed cable connections.

Electrical

White-on-Red Sign

Airfield sign presentation using a white legend on a red background, associated with mandatory-instruction sign applications where specified.

Signage

Wind Direction Indicator

A visual device that indicates wind direction and provides a practical surface reference for pilots during aerodrome operations.

Operations

Wiring Diagram

A drawing showing the physical wiring connections between components, including terminal numbers and cable references, used for installation and fault-finding.

Documentation

Witness Point

A stage in an Inspection Test Plan at which a specified party may observe the work or test but is not required to, and work may proceed if they choose not to attend.

Testing

Work Permit

The document, once issued and signed, that authorises named personnel to carry out defined work under specified conditions and time limits.

Documentation

Working at Height

Any work carried out where a person could fall a distance liable to cause injury, subject to specific controls such as fall protection or safe access equipment.

Operations

X

Xenon Flash Tube

A gas-discharge lamp filled with xenon gas used in strobe-type warning and obstruction lights to produce a brief, intense flash of light.

Fixtures

Y

Yellow-on-Black Sign

Airfield sign with a yellow legend on a black background, used for location signs such as the taxiway designation, so the pilot knows which surface the aircraft is on. Direction and destination signs use the reverse arrangement (black on yellow).

Signage

Z

Zero CheckInstrument Zero Check

A calibration step in which a test instrument is confirmed to read zero with no input signal present, performed before measurements to catch offset errors.

Testing

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Keyword Reference

Airfield Lighting Terminology & Glossary Notes

Airfield lighting terminology

Airfield lighting terminology is the shared vocabulary of the field: the names of lights, circuits, equipment, tests and standards. Using the same terms in specifications, drawings and fault reports avoids confusion between designers, contractors and maintenance staff.

Airfield lighting glossary

This airfield lighting glossary lists terms, abbreviations and short definitions across electrical systems, fixtures, photometry, testing, maintenance and standards. Use the search box and the category filters above to find a term, then follow the related pages for the full engineering explanation.

Runway touchdown zone lights

Runway touchdown zone lights are the rows of white lights in the touchdown zone of a precision approach runway, helping pilots judge the touchdown point and keep the aircraft aligned in low visibility. Their arrangement and use follow the applicable standard and the runway category.

Approach lighting spacing

Approach lighting spacing is the distance between lights or light bars along the approach lighting system. It is fixed by the system type and the standard, and it affects the pilot's visual cues and the length of cable needed on each circuit.

AGL maintenance records

AGL maintenance records are the logs of inspections, tests, faults, repairs and replacements for the lighting system. Good records show trends, support defect analysis and prove that the maintenance programme was carried out.

Frequently Asked Questions

Quick answers about using the AGL Glossary.

Q1How many terms are in the AGL Glossary?

1,033 terms, abbreviations, components and technical definitions used across Airfield Ground Lighting engineering, standards and field operations, organized into 27 letter groups and 10 categories.

Q2What categories does the glossary use?

Electrical, Fixtures, Systems, Photometry, Testing, Maintenance, Operations, Signage, Documentation and Standards. Each term is tagged with one of these categories, colour-coded for quick scanning.

Q3How do I find a specific term?

Use the search box to search across all 1,033 entries, or use the letter groups and category filters to browse. The Clear Filters option resets your search.

Q4Are abbreviations included, or just full terms?

Both. The glossary includes abbreviations and acronyms (such as A-SMGCS, AAI and ALCMS) alongside full terms and their definitions, so you can look up either form.

Q5Is the glossary a substitute for the official standards definitions?

No. It's a searchable reference for engineering and field terminology. For a definition that matters for compliance or a live project, confirm it against the current, officially published ICAO, FAA or national standard.

Q6Who compiled the AGL Glossary?

Precision AGL Academy, as part of the AGL Knowledge Hub, drawing on the terminology used across its training material and standards references.

Go Further

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