AGL-CS-099 — Complete Runway Lighting Failure: From CCR to Fixture
The AGL Knowledge Hub | Engineering Case Study Series. A master-level investigation of a complete runway edge lighting failure — from ALCMS command through PLC, CCR, primary circuit, isolating transformers, secondary circuits, connectors, and fixtures — demonstrating the complete AGL troubleshooting methodology.
Important: This is an engineering simulation created for training. It is not presented as an actual airport incident. All readings, values, dates and outcomes are illustrative, and no airport, organisation, person or manufacturer is identified or implied.
1Case Study Overview
During routine night operations, Runway 09/27 edge lighting failed completely immediately after the runway lighting circuit was energized from the ALCMS.
The operations center reported:
- Entire runway edge circuit dark.
- CCR available but abnormal.
- ALCMS alarm active.
- Remote control unsuccessful.
- No visible runway edge lights.
Because the failure affected the entire runway lighting system, a comprehensive investigation was initiated covering:
- ALCMS commands.
- PLC control logic.
- SCADA communication.
- CCR operation.
- Primary cable integrity.
- Insulation resistance.
- Isolating transformers.
- Secondary circuits.
- L-823 connectors.
- Individual light fittings.
- Photometric verification.
The investigation identified multiple contributing failures, with the primary cause being a primary-circuit insulation failure combined with secondary-connector water ingress, resulting in total loss of runway edge lighting.
This case demonstrates the complete engineering methodology for investigating a full runway lighting system failure.
2Learning Objectives
After completing this case study, the learner should be able to:
- Troubleshoot a complete runway lighting failure.
- Follow a structured AGL investigation sequence.
- Diagnose CCR abnormalities.
- Test primary-circuit integrity.
- Locate insulation failures.
- Investigate transformer and secondary faults.
- Restore complete runway lighting operation.
- Verify electrical and photometric compliance.
3System Background
A complete runway lighting system includes:
- ALCMS.
- SCADA.
- PLC.
- CCR.
- Primary series circuit.
- Isolating transformers.
- Secondary cables.
- L-823 connectors.
- Light fittings.
- Optical systems.
- Photometric performance.
Failure may occur in:
- Control systems.
- Communication systems.
- Power systems.
- Primary distribution.
- Secondary distribution.
- Connectors.
- Fixtures.
- Optical systems.
Successful troubleshooting requires system-level thinking.
4Problem Statement
The reported condition was:
- Entire runway edge circuit OFF.
- ALCMS alarm active.
- CCR abnormal.
- Field lights dark.
- Operational impact critical.
Where has the runway lighting system failed between the ALCMS command and the individual light fixture?
5Initial Observations
| Runway edge lights | OFF |
| CCR availability | Healthy |
| CCR output | Abnormal |
| ALCMS alarm | Active |
| Communication | Available |
A complete system investigation was required.
6Investigation Strategy
The investigation followed the sequence:
This prevents unnecessary component replacement.
7Test Equipment
The investigation used:
- CCR diagnostics.
- Digital multimeter.
- Insulation resistance tester.
- TDR.
- Transformer test equipment.
- Earth-fault locator.
- PLC diagnostics.
- ALCMS diagnostics.
- Photometer.
- Thermal imaging camera.
8Investigation
Step 1: Verify ALCMS Command
Results:
- Command transmitted.
- PLC received command.
- CCR start command executed.
- ALCMS communication healthy.
The control system was operational.
Step 2: Verify CCR Operation
Measurements:
| Input supply | Normal |
| Output current | Unable to regulate |
| Output voltage | Excessively high |
| Protection | Active |
The CCR indicated an open-circuit or high-impedance condition.
Step 3: Primary-Circuit Continuity
Continuity testing showed:
Open circuit
The primary circuit was interrupted.
Step 4: Insulation Resistance Testing
Measured insulation resistance:
0.9 MOhm
Expected:
≥ 100 MOhm
A significant insulation failure existed.
Step 5: TDR Investigation
TDR identified a fault approximately:
1.42 km from the CCR
The fault was localized in the field.
Step 6: Field Excavation
Inspection revealed:
- Damaged primary cable.
- Water ingress.
- Cable sheath deterioration.
- Earth leakage.
The primary cable had failed.
Step 7: Transformer Inspection
The nearest transformer showed:
- Water contamination.
- Secondary-terminal corrosion.
- Reduced insulation.
The transformer had suffered environmental damage.
Step 8: Secondary-Circuit Testing
Measurements showed:
- Secondary continuity intermittent.
- Connector resistance elevated.
- Moisture inside the connector.
Secondary degradation was also present.
Step 9: L-823 Connector Inspection
Inspection revealed:
- Water ingress.
- Corrosion.
- Carbon tracking.
- Incomplete sealing.
The connector was unreliable.
Step 10: Fixture Verification
The fixture itself was electrically healthy.
No major optical damage was observed.
Step 11: Photometric Verification
After temporary circuit restoration:
- Intensity normal.
- Beam alignment acceptable.
- Color compliance acceptable.
Photometric performance remained acceptable.
9Root Cause
The complete runway lighting failure resulted from combined primary-circuit insulation failure and secondary-connector water ingress, including:
- Primary cable insulation breakdown.
- Water-related earth leakage.
- Open-circuit development.
- Transformer moisture contamination.
- Connector corrosion.
- Secondary-circuit degradation.
The primary failure mechanism was primary-circuit failure, while secondary deterioration contributed to system instability.
10Corrective Action
The engineering team:
- Replaced the damaged primary cable section.
- Repaired cable joints.
- Replaced the affected transformer.
- Replaced the damaged L-823 connectors.
- Replaced secondary cable sections.
- Restored enclosure sealing.
- Performed insulation testing.
- Tested CCR regulation.
- Verified ALCMS operation.
- Conducted photometric verification.
11Post-Repair Verification
Complete system operation was restored.
12Integrated Root-Cause Analysis
Runway lights failed
Healthy
Healthy
Abnormal
Open
Failed
Fault located
Damaged
Moisture damage
Water ingress
System retested operational
Pass
Primary insulation failure with secondary environmental degradation
13Why This Case Was Important
This case integrated:
- ALCMS diagnostics.
- SCADA communication.
- PLC verification.
- CCR analysis.
- Primary-circuit testing.
- Insulation diagnosis.
- TDR fault location.
- Transformer investigation.
- Connector analysis.
- Fixture verification.
- Photometric testing.
It represents the complete AGL troubleshooting methodology.
14Engineering Lessons
Always investigate from the control system toward the field.
Always investigate from the control system toward the field.
CCR behavior provides critical diagnostic information.
CCR behavior provides critical diagnostic information.
Primary insulation testing should precede transformer replacement.
Primary insulation testing should precede transformer replacement.
Water ingress often creates multiple simultaneous failures.
Water ingress often creates multiple simultaneous failures.
Electrical restoration should always be followed by photometric verification.
Electrical restoration should always be followed by photometric verification.
15Master Troubleshooting Checklist
16Engineer's Decision Point
You observe: Entire runway edge circuit OFF. CCR unable to regulate current. Output voltage extremely high. ALCMS communication healthy. What should you investigate first?
17Knowledge Check
18Interview Questions
Quick Reference: Runway Lighting CCR Current
Runway lighting CCR current is the series current the CCR holds in the loop, set by the brightness step. If the whole runway is dark, check that the CCR is on, that its output current is correct at the selected step and that its alarms are clear. The current reading tells you whether the fault is at the CCR or in the loop after it.
19Frequently Asked Questions
Quick answers about complete runway lighting failure and the CCR-to-fixture methodology.
Q1What is AGL-CS-099?
AGL-CS-099 is an engineering training case study. It covers a complete Runway 09/27 edge lighting failure, investigated from the ALCMS command through to the individual fixtures. It is an engineering simulation created for training, not a report of an actual airport incident.
Q2What investigation sequence was used?
ALCMS, SCADA, PLC, CCR, primary cable, insulation, transformer, secondary cable, connector, fixture and photometry. Working in order prevents unnecessary component replacement.
Q3Was the control system at fault?
No. The command was transmitted, the PLC received it and the CCR start command executed, with ALCMS communication healthy.
Q4What did the CCR show?
Input supply was normal, but the CCR could not regulate current and output voltage was excessively high with protection active, indicating an open-circuit or high-impedance condition.
Q5How was the fault found in the field?
Continuity testing showed an open primary circuit and insulation resistance was 0.9 MΩ against at least 100 MΩ. TDR located the fault about 1.42 km from the CCR, where excavation found a damaged cable with water ingress, sheath deterioration and earth leakage.
Q6Were other components affected?
Yes. The nearest transformer had water contamination and terminal corrosion. Secondary continuity was intermittent, and L-823 connectors showed moisture, corrosion and incomplete sealing.
Q7What was the root cause of AGL-CS-099?
Primary-circuit insulation failure combined with secondary-connector water ingress. The primary mechanism was primary-circuit failure, with secondary deterioration adding instability.
Q8How was the runway lighting restored?
The team replaced the damaged primary cable section, repaired joints and replaced the affected transformer, L-823 connectors and secondary cable sections. They restored enclosure sealing, tested insulation and CCR regulation, verified ALCMS operation and conducted photometric verification.
Q9What is the key lesson from this case?
Use a systematic top-to-bottom method. Complete failures can have several contributing faults, so test each layer instead of replacing parts by guesswork.
Engineering & Expert Notes
Follow a Fixed Order From Control to Field
MethodWork through control, CCR, primary circuit, transformer, secondary and fixture in turn.
Test Primary Insulation Before Replacing Transformers
SequenceThis avoids replacing healthy units.
Expect Combined Faults After Water Entry
Multiple FaultsWater can cause several failures at once. Keep going after the first repair.
Keep a Written Log of Each Step and Result
RecordsThe log supports the handover and later analysis.
20Case Study Conclusion
A complete runway lighting failure must be investigated as an integrated system failure from the ALCMS command through the PLC, CCR, primary circuit, isolating transformers, secondary circuits, connectors, and fixtures, and effective troubleshooting requires systematic elimination of each subsystem rather than replacement of individual components.
Systematic control-system verification, CCR diagnostics, primary-circuit testing, insulation analysis, TDR fault location, transformer evaluation, connector inspection, fixture verification, and photometric testing provide a complete engineering methodology for restoring runway lighting safely and efficiently.
In AGL engineering, the runway light is only the final visible component of a much larger electrical, control, and automation system, and the engineer who understands the entire chain from the CCR to the fixture can solve failures that others can only observe.
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