Dedicated Monitoring System Solution for PAPI and SFLS

01  Background and Necessity

PAPI: Having the Equipment Is Not the Same as Having Monitoring

Operations management is concerned not only with whether the lights are lit, but also with seeing abnormalities in time, identifying the affected object and organising a follow-up check. Although some airports already have PAPI or a lighting monitoring system, the existing PAPI itself often does not include dedicated monitoring of angle, light source and communication status; the fact that a unit is still lit does not mean that all related feedback is normal.

For brownfield upgrades, the specific model and site conditions should be used to assess native-interface connection or external monitoring, to bring project-confirmed status into the station platform, identify the affected object first, and then carry out verification in accordance with airport procedures.

SFLS: Receiving a Control Command Is Not the Same as Confirming Flashing Status

SFLS is the sequenced flashing portion of the approach lighting system. Multiple flasher units normally flash in sequence from the outermost end toward the runway threshold, creating a dynamic visual cue that moves toward the runway, helping the crew identify runway direction and supporting the transition from instrument flight to visual flight.

This solution proposes that, based on the signals available to the project, a distinction be made between control commands, drive/electrical feedback, confirmed optical feedback, operating mode, timing feedback and communication status; when a link is lost, the system displays “communication unavailable or status unknown”, avoiding misinterpreting a communication break as a luminaire fault. The system only provides verification clues and does not replace on-site optical inspection or operational clearance.

Safety risk  The CAAC East China Regional Administration notice No. 5 of 2024 records that failure of a single PAPI light unit at an airport once had a certain impact on operational safety, and that existing monitoring did not cover secondary cable faults or PAPI light failure; this solution lists the alarming, locating and confirmation of a single-unit failure as a high-priority item for project verification (internal ranking of the solution).

02  Dedicated PAPI Monitoring

PAPI: From Seeing the Light to Early Warning

Supplementing the Monitoring Capability of an Existing PAPI

Background of the notice and priority for rectification  The CAAC East China Regional Administration Aviation Safety Notice No. 5 of 2024 (HDCAAC-SB-2024-05, 2024-02-22) records that failure of a single PAPI light unit at an airport had a certain impact on operational safety; thermal ageing and an exposed short circuit in the secondary cable/connector caused loss of supply to the luminaire incoming line, and existing monitoring did not cover secondary cable faults or PAPI light failure and raised no alarm. The notice was forwarded as an urgent plain-language telegram, requiring immediate investigation, insulation testing, replacement of affected parts and completion of single-unit failure monitoring/alarming or alternative measures. This solution lists it as a high-priority item for project verification (internal ranking of the solution).

A/B/C/D Status and Angle Warning

Where the existing PAPI does not include monitoring, a status acquisition and transmission unit can be assessed for retrofitting according to the model and site conditions. The platform displays project-confirmed feedback by A/B/C/D unit and gives an alert when angular deviation reaches a preset warning threshold, providing clues for inspection, calibration and maintenance planning.

· Applicability must be confirmed item by item according to the specific LED or halogen PAPI model;

· Displays the light source, angle-related feedback and communication status of connected units;

· Records warnings, alarms, acknowledgements, recovery and historical events.

What Operations Personnel Focus On

Early warning of light source and angle abnormalities  When key components such as the light source or angle deviate beyond a set threshold, the system gives an early warning, notifying the lighting station to pay attention and take early action in the light of operating status.

Safety boundary of the retrofit  The monitoring retrofit is used for maintenance prompts only; it does not adjust the optical angle or mechanical structure of the PAPI and has no effect on its calibration, photometric checks or the airport's clearance decision.

Communication status  Displays the various abnormal states accurately and in detail, without treating a communication break directly as a luminaire fault.

03  Dedicated SFLS Monitoring

Sequenced Flashing Lights System（SFLS）Status Monitoring

Flasher units, timing feedback and communication status brought together on one screen

When an abnormality occurs in the SFLS, operations personnel most need to know first: which flasher unit is affected, and whether it is a device-feedback problem or a communication problem. Based on the confirmed device mapping, the system presents the connected status, helping to narrow the scope of on-site verification.

· Displays the commands of connected flasher units;

· Displays the number of units and the operating mode according to project configuration;

· Presents device feedback abnormalities and communication abnormalities separately.

Pointing Abnormalities to a Specific On-Site Object

Unit locating  Displays flasher unit status by unit code, helping to locate the point requiring verification.

Communication status  Monitors the on-site units, the main control device and the data aggregation link; when a link is lost, it clearly displays status unknown.

04  Project Applications and Interfaces

PAPI Monitoring Project Application at Beijing Capital Airport

Project application interface of the PAPI monitoring system at Beijing Capital Airport (functions and scope subject to approved project documentation)

The project interface organises project-confirmed angle-related feedback, light source status and event information by A/B/C/D unit, so that operations and maintenance personnel can verify around the same object. The interface is used for status monitoring and O&M assistance; whether it includes control functions, and the specific permissions and interface boundaries, are subject to the approved project design. This interface is an illustration of the solution application only and does not constitute proof that the notice's rectification has been completed or a compliance assessment.

Power line carrier  Uses the existing lighting circuit to carry monitoring communication.

Standalone dedicated platform (optional)  Where the existing platform does not yet have the interface conditions, status, alarms and historical queries can be deployed independently.

Existing ALCMS interface (optional)  After the open interface, protocol, point list and network boundary are confirmed, a status interface can be provided.

05  Operational Value and Implementation

What Operations Management Ultimately Gains

Keep the technical complexity inside the system and the information operations personnel need on the interface: the affected object is clearer, angle risk can be flagged in advance, the event process is traceable, and the retrofit path can be chosen in the light of existing conditions.

Enhanced monitoring  For scenarios where a PAPI already exists but without monitoring, the monitoring capability can be effectively strengthened.

Early warning  Flags light source and angle-related changes at preset warning points, buying time for on-site verification and maintenance planning.

Abnormalities have direction  Distinguishes status abnormalities, communication abnormalities and unknown states by device identifier, reducing undirected troubleshooting.

Project practice  The project interface and application experience at Beijing Capital Airport can serve as a reference for similar retrofits.

Closed loop for safety risk  Against the blind spot exposed by the notice — a single-unit failure with no monitoring alarm — our solution can achieve a complete closed loop.

From Site Survey to System in Service

1. Confirm current state and objectives  Confirm the PAPI and SFLS models, the existing system and available interfaces.

2. Retrofit and interface design  Determine the communication method, the warning or alarm logic and the system architecture.

3. Staged installation and verification  Implement within the approved window and verify acquisition, link loss, warning, recovery and the impact on existing functions.

4. Training, handover and operation  Hand over approved drawings, software or configuration baselines and test records, and put the system into service in accordance with airport procedures.