Airfield Ground Lighting is not just about installing lights. It is about controlling, monitoring, and ensuring every light performs exactly when required. This is where the Airfield Lighting Control and Monitoring System (ALCMS) comes in.
ALCMS connects the control-room operation with the field lighting infrastructure, allowing operators to set lighting requirements while continuously receiving information about system status and faults. In simple terms, ALCMS is the brain of the entire airfield lighting system.
- 01 What Is ALCMS?
- 02 Why ALCMS Is Critical
- 03 Main Functions of ALCMS
- 04 Fault Detection & Alarm System
- 05 Redundancy & Backup Logic
- 06 Key Components of ALCMS
- 07 How ALCMS Works – Simplified Flow
- 08 Common Field Issues
- 09 Best Practices for Reliability
- 10 ALCMS in Modern Airfield Operations
- 11 Key Takeaways
- 12 Frequently Asked Questions
ALCMS is the brain of the entire airfield lighting system. It brings operation, monitoring, fault indication, communication, and redundancy together into a single safety-critical system.
What Is ALCMS?
ALCMS is the central system used to:
- Control airfield lighting circuits
- Monitor real-time performance of AGL components
- Detect faults promptly
- Support safe aircraft operations at night and in low visibility
It connects the control-room operation with the field lighting infrastructure, allowing operators to set lighting requirements while continuously receiving information about system status and faults.
Why ALCMS Is Critical
Airfield lighting is directly linked to flight safety. Any delay, failure, or incorrect intensity can create serious risk during landing approach, take-off roll, and taxiing operations. ALCMS helps ensure:
- Correct light intensity matched to visibility (for example RVR), as selected by the operator or ATC procedure
- Prompt fault detection
- Reduced dependency on manual switching
- Faster response during emergencies
In modern airport operations, the ability to control and monitor AGL systems centrally is extremely important. For runways used in low-visibility operations, ICAO Annex 14 also expects a monitoring system that shows the operational status of the lighting, so that loss of serviceability beyond the permitted limits is known to the operator (confirm the clause and limits in your current edition and national regulation).
Main Functions of ALCMS
Remote control typically covers circuits such as the following, along with others like runway centreline and touchdown zone lights, stop bars, PAPI and signs where connected:
Fault Detection and Alarm System
A critical function of ALCMS is detecting faults and promptly notifying operators. Typical functions include:
- Open-circuit detection
- Earth-fault and insulation-resistance deterioration alarms
- CCR trip, overcurrent and load-deviation alarms
- Individual lamp failure indication, in advanced systems
- Audio-visual alarms for operators
Individual lamp indication needs a system with single-lamp monitoring; most circuit-level systems report load changes only. When an abnormal condition occurs, the system provides an indication so the responsible team can investigate and act — reducing the time between fault occurrence and operator awareness.
Redundancy and Backup Logic
A good ALCMS system should include appropriate redundancy and backup arrangements, including:
- Main + standby control system
- Automatic changeover
- Fail-safe operation, with local control at each CCR as a fallback if ALCMS fails
- Secondary power supply with switch-over within the times set in ICAO Annex 14
The reason is simple: system failure is not an option in aviation. Redundancy ensures that the loss of one control element does not unnecessarily compromise the operation of the airfield lighting system.
Regular testing of the standby, changeover, local-control fallback and secondary-power switch-over functions is an important maintenance activity.
Key Components of ALCMS
An ALCMS typically includes several interconnected elements that together form its communication and control architecture:
How ALCMS Works – Simplified Flow
The basic operating sequence can be understood in six steps, forming a continuous control-and-feedback loop between the operator, ALCMS, CCR, and field lighting system:
The ALCMS Control-and-Feedback Loop
Operator Command → PLC/SCADA → CCR → Field Lights → Feedback & Alarms
Common Issues Seen in the Field
From practical field experience, several issues can affect ALCMS performance:
- Communication failure between CCR and the control system
- Incorrect configuration of intensity steps
- False alarms caused by poor earthing
- Delay in fault indication due to system lag
- Lack of proper redundancy testing
ALCMS is only as good as its configuration and maintenance. Even a technically advanced control system can become unreliable if communication, configuration, earthing, redundancy, or maintenance practices are not properly managed.
Best Practices for ALCMS Reliability
To maintain reliable operation, several practices are important:
- Conduct regular system health checks
- Perform periodic redundancy testing
- Ensure proper integration with CCRs and field circuits
- Monitor and analyse event logs
- Provide proper training to operators
- Put circuits in local/off and locked out at the CCR during maintenance, so remote commands cannot energise them
Event logs are particularly valuable because they provide information about system behaviour and historical faults. Operator training is equally important, because the effectiveness of a control and monitoring system ultimately depends on the people responsible for operating and responding to it.
ALCMS and Modern Airfield Operations
Modern airfield operations require more than simply switching lights ON and OFF. The system must know:
- What lighting has been commanded
- What intensity has been selected
- Whether the equipment is responding correctly
- Whether a circuit or fitting has developed a fault
- Whether the operator needs to take action
ALCMS provides this centralised control and monitoring capability, particularly under low-visibility conditions where managing the airfield lighting system becomes significantly more difficult without it.
Key Takeaways
- ALCMS is the central control and monitoring brain of the airfield lighting system, not just a control panel
- It works with CCRs to deliver step-wise intensity control, typically 3 or 5 steps, set by the project specification and applicable ICAO/FAA guidance
- Real-time monitoring and fault detection identify developing issues before they become complete failures
- Redundancy and fail-safe backup logic are essential — system failure is not an option in aviation
- Field issues usually trace back to communication, configuration, earthing, or maintenance gaps rather than the technology itself
- Reliable ALCMS operation depends as much on event-log analysis and operator training as it does on hardware
Conclusion
ALCMS is not just a control panel. It is a safety-critical system that helps ensure the right light, at the right intensity, at the right time.
Without effective control and monitoring, managing modern airfield lighting systems becomes significantly more difficult, particularly under low-visibility conditions.
ALCMS therefore plays a central role in connecting the operator, CCR, communication network, and field lighting infrastructure. In this article, I share practical insights on how ALCMS works, based on real field and project execution experience.
AGL provides the visual guidance, CCR controls the current, and ALCMS controls and monitors the complete operation.
Frequently Asked Questions
What is an Airfield Lighting Control and Monitoring System (ALCMS)?
ALCMS is the central system used to control airfield lighting circuits, monitor the real-time performance of AGL components, detect faults promptly and support safe aircraft operations at night and in low visibility. It connects the control room with the field lighting infrastructure, so operators can set lighting requirements while receiving continuous status and fault information.
Why is ALCMS critical to airfield operations?
Airfield lighting is directly linked to flight safety, and any delay, failure or incorrect intensity can create serious risk during approach, take-off roll and taxiing. ALCMS helps ensure correct intensity matched to visibility, prompt fault detection, reduced dependency on manual switching and faster emergency response. For low-visibility runways, ICAO Annex 14 also expects a monitoring system showing the operational status of the lighting, so confirm the clause and limits in your current edition and national regulation.
How does ALCMS control light intensity?
ALCMS works with Constant Current Regulators (CCRs), typically providing 3-step or 5-step brightness control, with 5 steps common on precision-approach and low-visibility runways. ALCMS sends the command and the CCR adjusts the current in the series circuit. Steps are selected for visibility and ambient light under the aerodrome's approved procedures.
What faults can an ALCMS detect?
Typical functions include open-circuit detection, earth-fault and insulation-resistance deterioration alarms, CCR trip, overcurrent and load-deviation alarms, and audio-visual alarms for operators. Individual lamp failure indication needs a system with single-lamp monitoring, because most circuit-level systems report load changes only.
What redundancy and backup logic should an ALCMS have?
A good ALCMS should include a main and standby control system, automatic changeover and fail-safe operation, with local control at each CCR as a fallback if ALCMS fails. It should also include a secondary power supply with switch-over within the times set in ICAO Annex 14, and the standby, changeover, local-control fallback and power switch-over functions should be tested regularly.
What are the key components of an ALCMS?
A typical ALCMS includes operator workstations with an HMI/SCADA interface, PLC-based control panels, a communication network such as fibre or Ethernet, CCR interface panels and field monitoring units that report actual field conditions back to control.
How does ALCMS work in simple steps?
The operator selects the lighting requirement based on ATC instruction or visibility, the command is sent through the PLC/SCADA control system, and the CCR changes the series-circuit current. The lights respond, field and equipment status signals return to the control system, and any fault is displayed to the operator with an alarm.
What common issues affect ALCMS reliability and how are they avoided?
Common field issues include communication failure between the CCR and the control system, incorrect configuration of intensity steps, false alarms caused by poor earthing, delayed fault indication and lack of redundancy testing. Good practice includes regular health checks, periodic redundancy testing, event-log analysis, operator training, and putting circuits in local/off and locked out at the CCR during maintenance so remote commands cannot energise them.