How do you troubleshoot an ALCMS problem from the symptom?
The symptom shows which layer failed, from the screen down to the CCR and the circuit, and a short set of checks confirms it, starting with the simplest cause.
The ALCMS is built in layers: control positions, duplicated servers, two network paths, field controllers, the CCRs and the circuits they feed. Commands travel down and status and alarms travel back up, so the symptom points to a layer. A communication alarm or stale status points to the server, network or field controller. A command ignored may only mean the CCR selector is in Local or Off, which is not a fault. A CCR alarm or no output current points to the CCR or its circuit, and CCR normal but lights wrong moves the search to the circuit and fixtures.
A failed link can leave the screen blank or out of date, so a quiet screen is not proof of a healthy airfield and status is checked at the CCR or in the field. ATC is told first, only authorised engineers work on the equipment, and after repair and test the selector is returned to Remote and status confirmed before ATC is told control is restored. The failure flow entry shows what the system does when something fails, and the troubleshooting flow entry traces it layer by layer. This entry starts from what the operator sees. Alarm codes and exact checks come from the manufacturer and project documents.
Frequently Asked Questions
Q1Why does the ALCMS screen not always show the true state of the lights?
A failed link or field controller can leave the display blank or frozen on old values, so a quiet screen is not proof of a healthy airfield. Status is checked at the CCR or in the field, not read from the screen alone.
Q2Why do lights ignore a command from the ALCMS?
The CCR selector may be in Local or Off. A CCR in either position ignores remote commands, which is not a fault. The selector position is checked before looking for a communication or CCR fault, and it is returned to Remote after any work.
Q3What does a communication alarm point to?
A fault above the CCR: the server, the network path or the field controller. Servers and network paths are normally duplicated, so one failure does not remove control, but the alarm tells the operator that something needs repair.
Q4What if the CCR shows an alarm or no output current?
The fault is then in the CCR or its circuit, such as an open circuit, overcurrent or earth leakage, rather than in the control system. It is isolated and repaired under the airport procedure, using the CCR and series-circuit troubleshooting entries.
Q5What if the CCR output is normal but the lights are wrong?
The control layers are working and the search moves to the circuit and the fixtures: connectors, transformers, cable and the lights themselves. Circuit status shows the health of the whole loop, so a single failed light may not appear on the screen.
Q6What is done before and after ALCMS troubleshooting?
ATC is told first, only authorised engineers work on the equipment, and lighting pilots need is secured. After repair and test, the selector is returned to Remote and status is confirmed before ATC is told that control is restored.
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