ALCMS Event Logger

The ALCMS Event Logger is the central logging and audit trail subsystem of the Airfield Lighting Control and Monitoring System. It is responsible for capturing every significant occurrence within the AGL network — from CCR status changes and circuit switching actions to operator logins, alarm activations, and system health events — and storing them in a secure, searchable, and tamper‑evident database. The Event Logger provides the foundation for compliance reporting, fault analysis, predictive maintenance, and operational transparency.

Key characteristics of the ALCMS Event Logger include:

• Comprehensive Event Capture: Logs all system events including CCR power changes, brightness step selections, circuit ON/OFF transitions, alarm activations and clears, operator commands, system startup/shutdown, communication status, and configuration changes.
• High‑Resolution Timestamping: Each event is timestamped with sub‑second precision (typically 1 ms or better) using a synchronized time source (GPS/NTP), enabling accurate sequence‑of‑events (SOE) reconstruction.
• Immutable Storage: Logs are stored in a write‑once, read‑many (WORM) database or with cryptographic hashing to prevent tampering, ensuring audit trail integrity for regulatory compliance.
• Scalable Retention: Supports configurable retention policies — from weeks to years — with automatic archiving and purging to manage storage capacity.
• Powerful Query & Filtering: Provides advanced search, filtering, and reporting capabilities based on time range, event type, device, user, and severity, enabling rapid fault diagnosis and trend analysis.
• Real‑Time and Historical Views: Offers both real‑time event streaming (for live monitoring) and historical retrieval (for post‑event analysis) through a unified interface.
• Export & Reporting: Supports export of logs in standard formats (CSV, XML, PDF) for regulatory submissions, maintenance records, and incident reports.
• Integration with ALCMS: Seamlessly integrates with the ALCMS server, workstations, and other subsystems, receiving events via system bus (e.g., OPC UA, MQTT, or proprietary API).

The Event Logger is typically implemented as a software service running on the ALCMS server or on a dedicated database server, with optional hardware acceleration for high‑throughput environments. It is a critical component for maintaining operational safety, regulatory compliance (FAA, ICAO), and continuous improvement of airfield lighting operations.

The event logger exists because, without it, everything the AGL system does happens and then simply vanishes — a fault clears, an operator issues a command, a circuit switches, and none of it can be proven to have happened a certain way at a certain moment once it's over. That absence becomes a real problem the moment something goes wrong: an incident investigation, a regulatory audit, or a pattern of recurring faults all depend on being able to reconstruct exactly what the system was doing and when. By capturing every event with sub-second, synchronised timestamps and storing them in a tamper-evident form, the logger turns operation that would otherwise be unverifiable after the fact into a permanent, trustworthy record — which is what allows root causes to be found with confidence rather than guessed at, and what gives regulators and the airport operator demonstrable evidence of compliant operation rather than an unverified claim of it.

The ALCMS Event Logger is deployed in every airfield that requires a robust audit trail for its AGL system. Key applications include:

• ALCMS Server Core: Running as a background service on the ALCMS server to capture all system‑wide events.
• Regulatory Compliance: Providing the documented evidence required by FAA, ICAO, and other regulatory bodies for AGL system operation and maintenance.
• Incident Investigation: Enabling post‑event reconstruction of system behavior to determine root causes of failures, alarms, or operational errors.
• Predictive Maintenance: Analysing event patterns (e.g., repeated fault occurrences, gradual performance degradation) to predict and prevent equipment failures.
• Operator Accountability: Recording all operator actions (logins, commands, parameter changes) to ensure traceability and accountability in critical operations.
• System Performance Monitoring: Tracking system response times, communication latencies, and resource utilization to optimize AGL system performance.
• Data Integration: Feeding logged data into higher‑level airport management systems, enterprise asset management (EAM) systems, or big data analytics platforms.
• Training and Simulation: Using historical event logs to create realistic training scenarios for operators and maintenance personnel.

The Event Logger is installed as a software service on the ALCMS server itself or on a dedicated database server in the main control centre, so it has a direct, low-latency path to the system bus events it captures rather than being deployed at any remote field location. Its storage — whether local disk, a SAN volume, or the ALCMS database server's own storage — is sized for the retention period specified (weeks to years) and is included in the facility's backup and archiving regime, since the write-once audit trail has no value if the storage holding it is lost to a single hardware failure. Where WORM (write-once, read-many) storage or cryptographic hashing is used for tamper-evidence, that storage is configured at installation time and is not something reconfigured casually afterward, since doing so would undermine the integrity guarantee the logger exists to provide. Time synchronisation to the facility's GPS/NTP reference is confirmed as part of commissioning, since the sub-second timestamp accuracy the logger depends on for sequence-of-events reconstruction is only as good as the time source feeding it.

The ALCMS Event Logger operates as a high‑performance event processing and storage engine. Key functional aspects include:

• Event Source Integration: The logger subscribes to event streams from various AGL subsystems via standard communication protocols (OPC UA, MQTT, Modbus, or proprietary APIs). It listens for events such as status changes, alarms, operator commands, and system health messages.
• Event Validation and Enrichment: Each incoming event is validated for completeness and correctness. The logger enriches the event with additional metadata — such as the source device type, location, operator ID (if applicable), and a system‑wide unique event ID.
• Timestamping: The logger applies a precise timestamp (typically from the system’s synchronized time source) to each event. If the event already carries a timestamp from the source, the logger may use either the source timestamp or its own, depending on the configuration.
• Event Classification and Prioritization: Events are classified into categories (e.g., alarm, status, command, system, informational) and assigned a severity level (critical, major, minor, warning, info). This enables efficient filtering and reporting.
• Persistent Storage: Events are stored in a robust database (SQL or NoSQL) with write‑ahead logging and transaction support to ensure data integrity. The storage engine is optimized for high‑throughput insertion (thousands of events per second) and fast retrieval.
• Indexing and Compression: To support fast queries, the logger maintains indexes on key fields (timestamp, device, event type, user). Data compression techniques (e.g., columnar storage, delta encoding) are applied to reduce storage footprint without sacrificing query performance.
• Retention Management: The logger enforces configurable retention policies — for example, keeping detailed logs for 90 days and aggregated summaries for 5 years. Automatic archiving to cheaper storage (tape, cloud) or purging of old data is performed to manage capacity.
• Real‑Time Streaming and Query API: The logger provides both a real‑time event stream (for live dashboards and alarm monitoring) and a historical query API (for reports, investigations, and data exports). Access is secured with role‑based permissions.
• Audit Trail Integrity: To prevent tampering, the logger may employ cryptographic hashing (blockchain‑like chaining) of events or store logs in a WORM (write‑once, read‑many) file system. All modifications (e.g., manual annotations) are also logged with full traceability.

The Event Logger is designed for high availability, with redundant storage and failover capabilities. It is typically backed up regularly to off‑site storage to protect against data loss. The system includes comprehensive monitoring of its own health (disk space, throughput, error rates) and can generate alerts if the logging service is degraded.

The event logger runs on a rack-mount server (typically 1U to 2U) or as a virtual appliance on shared server infrastructure, built with the same rack-rail mounting, hot-swappable power supply, and RAID 10 storage conventions as other server-room AGL computing equipment. SSD storage handles the high-ingest write path for incoming events, while larger HDD volumes are used for long-term tiered archive storage within the same chassis, allowing the retention policy to span from fast recent-event queries to multi-year compliance archives without moving hardware platforms. Network interfaces are brought out through rear panel-mounted RJ-45 or SFP connectors, and where the logger is deployed as a physical appliance rather than a virtual machine, dual power supplies are fed from independent circuits so a single power-path failure does not interrupt event capture. The unit is installed in the same conditioned server room or data-centre rack as the ALCMS server it supports, with the standby node in an active-passive cluster sited in a separate rack to preserve redundancy against a single local fault.