What happens when the ALCMS fails?
A failure in a server, network path, field controller or CCR has a different effect at each layer, and in every case ATC is told and the lighting is secured.
The effect of a failure depends on which layer fails. A failed server or a lost network path is covered by its duplicate, so remote control continues and an alarm tells the operator that something needs repair. If a field controller or its link is lost, the CCRs normally hold their last commanded state, remote commands stop, and the lighting is set by local control at the substation or CCR. A CCR or circuit fault affects that circuit directly and is isolated and repaired under the airport procedure.
In every case the order is the same: tell ATC, secure the lighting pilots need, have authorised engineers repair and test, and return to remote control only when status is confirmed. A failed link can leave a display blank or out of date, so status is checked at the CCR or in the field, not read from the screen alone. The exact behaviour depends on the system design and its fail-safe settings.
Frequently Asked Questions
Q1Does one ALCMS failure switch the airfield lights off?
Not normally. Servers and network paths are duplicated, and CCRs usually keep their last commanded state if communication is lost. The exact behaviour depends on the system design and its fail-safe settings, so it is confirmed from the project documents.
Q2What is the difference between losing communication and losing a CCR?
If communication is lost, the lights usually keep working but remote control and status feedback are lost for the affected part. If a CCR or circuit fails, the lights on that circuit are affected and an alarm is raised.
Q3How do operators know that a failure has happened?
Through alarms and status indications at the control positions, including communication-lost alarms. A lost link can also leave a display blank or out of date, so status is confirmed at the CCR or in the field and not taken from the screen alone.
Q4When is local control used?
When remote control is not available, or when the lighting must be set from site during a failure. It is done at the CCR or substation under the airport procedure and agreed with ATC, because the tower can no longer change the setting from its own position.
Q5Who must be told when the ALCMS has a failure?
ATC and airport operations first, because they rely on the lighting and may need to change operations or issue notices. The maintenance team and the responsible engineers are told next, and the failure is recorded.
Q6When can remote control be restored?
After authorised engineers have repaired and tested the faulty part, the status shown on the ALCMS matches the equipment at the CCR, and ATC has been told that remote control is back.
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