What is fault indication?
How a fault is shown — by the lights, the CCR and the control screen — so the operator and maintainer know what kind of fault it is and where to start looking.
Fault indication is how the lighting system shows that something is wrong and where to start looking. It is built from three things read together: what the lights are doing, what the CCR reports (current, voltage, lamps, codes, contacts) and what the control system displays. Each fault type leaves a different pattern.
An open circuit darkens the whole circuit with no loop current. A short circuit bypasses part of the loop, so the lights in the shorted section go dark, and the CCR holds its current at a lower voltage. An earth fault usually leaves the lights on, so only leakage monitoring or testing shows it. A failed light sits on the transformer secondary, so only that light goes out. A communications fault leaves the screen stale while the field carries on. The indication gives a symptom and a zone; the cause is confirmed in the field after isolation. This page is the system-level picture; the CCR’s own lamps and codes are covered under CCR Fault Indication.
- Observe. Note the lights, output current and voltage, CCR indication and screen.
- Match. Compare the pattern with the fault types to find the likely fault and level.
- Record. Write down the indication, readings and time before any reset.
- Isolate. Lock out the supply and prove the circuit dead before field work.
- Confirm and fix. Test and inspect to find the cause, repair, then restore and verify.
Fault Indication Explorer
What is the symptom?
What is seen LIGHTS · CCR · SCREEN
What it suggests NOT A DIAGNOSIS
Teaching simulation. Patterns are typical for a series circuit with isolation transformers; actual indications and wording vary by equipment and project design.
Frequently Asked Questions
Q1What is fault indication?
The way the lighting system shows that something is wrong and where. It combines what the lights are doing, what the CCR reports and what the control system displays, so the operator and maintainer know the symptom and the zone to investigate.
Q2How is this different from CCR fault indication?
CCR fault indication covers the lamps, codes and contacts on the regulator itself. Fault indication here is the system-level picture: how those signals, the circuit behaviour and the control-system display are read together to tell an open circuit from a short circuit, an earth fault, a single light or a communications fault.
Q3Does an indication tell me the cause?
No. It points to a symptom and a place to start looking. The cause is confirmed by testing and inspection in the field, after the circuit has been isolated and proved dead.
Q4Why do some faults give no obvious sign?
A single earth fault leaves the series loop closed, so the lights usually stay on. Only leakage monitoring or insulation testing reveals it. Likewise a failed lamp sits on the transformer secondary, so the circuit stays up and only that light is out.
Q5What if the screen shows no fault but the field disagrees?
Trust the field. A lost link or field unit can leave the screen showing old values. A communications-lost alarm is itself a fault indication, and status should then be checked at the CCR or on the airfield.
Q6Should the fault be reset as soon as it is indicated?
No. Record the indication, readings and time first, then isolate and lock out and find the cause. A reset clears the evidence and can re-energise a circuit that still has the fault.
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