Runway Edge Light Troubleshooting

Equipment / System

Elevated omnidirectional or inset unidirectional/bidirectional runway edge light, isolating transformer (typically 6.6/6.6A or 200W/45W series-circuit type), series circuit loop fed from the runway edge CCR.

Possible Causes

Required Tools

Safety Precautions

• Runway edge series circuits operate at high voltage (up to several kV) under load — never open a transformer connector or fixture while the circuit is energised.
• Coordinate with ATC/airside operations before approaching the runway for inspection; obtain a runway inspection/works clearance.
• Apply LOTO at the CCR before any circuit continuity or insulation testing.

Diagnostic Procedure

1. ObservationFrom the CCR/ALCMS, confirm the series circuit is energised and the regulated current matches the commanded intensity step — this confirms the circuit itself is live.
2. ObservationConduct a visual runway inspection (or review the latest daily/periodic inspection record) to identify exactly which fixture(s) are dark and their position/circuit number.
3. DecisionSingle fixture dark → proceed to EDG-162 (Single Edge Light Failure). Multiple fixtures in a run dark → proceed to EDG-163 (Multiple Edge Lights Failure). Entire circuit/runway dark → proceed to EDG-164 (Runway Edge Lights Completely Off).
4. Fault LocationRecord the fixture position, circuit/loop identifier, and cable route reference to support the follow-on specific topic.

Test Points

Root Cause Verification

This topic is a triage entry point; verification is completed under the specific follow-on topic (EDG-162/163/164) once the fault scope has been confirmed.

Corrective Action

• No corrective action at this stage — route to the applicable specific topic based on the observed scope of the failure.

Preventive Action

• Maintain an up-to-date fixture position and circuit-loop reference map to speed scope triage.
• Ensure daily/periodic runway inspection records capture exact fixture identifiers, not just general location.

Related References

SOP: SOP-EDG-01 (Runway Edge Light Daily Inspection), SOP-EDG-02 (Runway Edge Fault Triage)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Individual elevated or inset runway edge fixture and its dedicated isolating transformer, fed in series from the runway edge circuit loop.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO the runway edge circuit at the CCR before disconnecting any primary connector.
• Verify zero energy at the transformer primary with a proven meter before handling — series circuits can retain induced voltage.
• Obtain airside/runway access clearance before working at the fixture location.

Diagnostic Procedure

1. ObservationConfirm only the single fixture is affected and adjacent fixtures on the same loop are operating normally, ruling out a loop-level fault.
2. MeasurementWith the circuit isolated and LOTO applied, measure the isolating transformer secondary output using a known-good primary current injection test set or a portable series circuit tester.
3. MeasurementIf the transformer output is present but the fixture does not light, test the LED module/lamp and driver (if fitted) directly.
4. MeasurementIf the transformer output is absent, disconnect the primary connector and inspect for corrosion, moisture, or a broken pin; megger the transformer primary and secondary windings.
5. DecisionTransformer output present, fixture dead → lamp/LED/driver fault. Transformer output absent, primary connector sound → transformer fault. Transformer output absent, primary connector damaged → connector/cabling fault.
6. Fault LocationIsolate to the transformer, the primary connector, or the fixture lamp/LED/driver assembly.
7. Root CauseConfirm the specific failed component by substitution with a known-good spare before closing out.

Test Points

Root Cause Verification

After replacement, re-energise the circuit and confirm the fixture lights at all intensity steps, and remains stable through a full step-up/step-down cycle.

Corrective Action

• Replace the failed LED module/lamp.
• Replace the failed isolating transformer.
• Clean, dry, and reseat the primary connector, or replace if corroded/damaged.
• Replace the failed LED driver.
• Repair or replace damaged fixture base wiring.

Preventive Action

• Include primary connector inspection and megger testing in the periodic runway edge light PM programme.
• Maintain isolating transformer and LED module spares at site stores for rapid single-fixture restoration.
• Log individual fixture/transformer failure history to identify recurring problem locations.

Related References

SOP: SOP-EDG-03 (Single Fixture Fault Isolation), SOP-EDG-05 (Isolating Transformer Test Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge circuit loop section, primary cable run, and multiple isolating transformer/fixture assemblies in that section.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO the full runway edge circuit before any cable joint or splice pit work.
• Treat all affected cable sections as potentially live until proven de-energised, given possible partial short conditions.
• Coordinate with airside operations and any concurrent civil works crews before excavation-related fault investigation.

Diagnostic Procedure

1. ObservationMap the exact fixtures affected and confirm they form a contiguous downstream section of the loop rather than being randomly distributed — this points toward a shared upstream cause.
2. MeasurementWith the loop isolated, measure primary cable continuity and insulation resistance section by section, working from the last known-good fixture toward the first affected fixture.
3. MeasurementWhere accessible, inspect splice pits/handholes in the affected section for water ingress, corrosion, or a physically damaged joint.
4. MeasurementIf a TDR is available, use it to localise a suspected open or short in the primary cable to a specific cable length from a known reference point.
5. DecisionOpen/high-resistance joint found → cable/joint fault at that location. Continuity and insulation normal at all joints → investigate individual transformers as coincidental multiple failures.
6. Fault LocationIsolate to the specific splice pit, joint, or cable section responsible for interrupting the downstream section.
7. Root CauseConfirm the physical cause — corrosion, water ingress, mechanical damage, or manufacturing defect — at the identified joint or cable section.

Test Points

Root Cause Verification

After repair, re-energise the loop and confirm all previously affected fixtures illuminate correctly at every intensity step, and re-megger the repaired section to confirm insulation resistance is within baseline.

Corrective Action

• Repair or replace the damaged primary cable section.
• Remake the faulty splice/joint using an approved airfield-rated jointing kit.
• Pump out and reseal a water-ingressed splice pit.
• Replace any individual transformers confirmed faulty in addition to the cable fault.

Preventive Action

• Include periodic insulation resistance testing of the full series circuit loop, section by section, in the PM programme.
• Inspect and reseal splice pit lids/gaskets on a scheduled basis to prevent water ingress.
• Coordinate with civil/works contractors before any excavation near known cable routes.
• Maintain an accurate as-built cable route drawing, updated after any repair.

Related References

SOP: SOP-EDG-06 (Series Circuit Loop Insulation Testing), SOP-EDG-07 (Splice Pit Inspection Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46, IEC 60364

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Splice Pit/Handhole Layout

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge CCR and its complete series circuit loop, including main isolator, primary feeder cable, and the full run of fixtures.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO the CCR output isolator before any loop-level testing.
• A complete loop-off condition with a tripped CCR protection relay may indicate a hazardous short — do not repeatedly reset the CCR without first confirming loop insulation resistance is within safe limits.
• Coordinate with ATC to confirm the runway lighting status and any operational impact before commencing fault-finding.

Diagnostic Procedure

1. ObservationCheck the CCR front panel/ALCMS for run status, output current, and any active alarm or trip indication.
2. DecisionCCR shows no output/fault indication → refer to Division 01 (CCR Troubleshooting) for the specific CCR fault topic before proceeding further.
3. MeasurementIf the CCR confirms normal regulated output but the entire runway remains dark, measure current at the CCR output terminals and again at the first fixture in the loop to confirm current is actually leaving the CCR cabinet.
4. MeasurementWith the loop isolated, megger the full series circuit loop to check for a low-resistance short that may be preventing normal circulation of current.
5. DecisionOutput confirmed leaving the CCR but not reaching the first fixture → break in the feeder between CCR and the runway. Output present at the first fixture but the rest of the loop dark → loop break further along the run.
6. Fault LocationProgressively test loop continuity moving along the runway from the CCR end to localise the specific break point.
7. Root CauseConfirm the exact cable section, joint, or connector responsible for the complete loop interruption.

Test Points

Root Cause Verification

After repair, re-energise the full circuit under supervision and confirm normal current regulation and full runway illumination at every intensity step before returning the runway to service.

Corrective Action

• Refer to and close out the applicable Division 01 CCR topic if the root cause is CCR-side.
• Repair the specific cable break/joint identified in the loop.
• Reset and re-energise the runway edge circuit from ALCMS/local panel once the fault is cleared.
• Replace a failed CCR output isolator/breaker.

Preventive Action

• Include full-loop insulation resistance testing as a scheduled PM activity, not only a reactive one.
• Maintain clear escalation procedure between CCR-side and loop-side fault diagnosis to avoid delay in a total-outage scenario.
• Ensure redundancy/backup CCR arrangements (where provided) are tested periodically.

Related References

SOP: SOP-EDG-08 (Total Runway Edge Outage Response), SOP-CCR-04 (CCR Isolation & LOTO Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, CCR Single Line Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge fixture (LED module or lamp), isolating transformer, and the associated primary series circuit connection.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture or transformer enclosure for internal inspection.
• Use appropriate eye protection when taking close-range light output readings on an energised fixture from outside the enclosure.

Diagnostic Procedure

1. ObservationVisually compare the affected fixture against immediately adjacent fixtures at the same intensity step, ideally at night or in a darkened hangar test setup.
2. MeasurementTake a luminous intensity/lux reading at a fixed distance and angle from the affected fixture and compare against a known-good reference fixture at the same step.
3. MeasurementWith the circuit isolated, measure isolating transformer secondary output and compare against nameplate rating.
4. ObservationInspect the lens/optical surface for dirt, haze, or discolouration that could account for reduced output even with normal electrical supply.
5. DecisionTransformer output normal, lens clean, output still low → LED module/lamp degradation. Transformer output below nameplate → transformer fault. Lens dirty/hazed → optical fouling, not an electrical fault.
6. Fault LocationIsolate to the LED module/lamp, the isolating transformer, or the optical surface as the source of reduced output.
7. Root CauseConfirm by substitution — swap in a known-good LED module or transformer and re-measure.

Test Points

Root Cause Verification

After corrective action, re-measure luminous intensity output and confirm it is within the manufacturer-specified tolerance of a known-good reference fixture at the same intensity step.

Corrective Action

• Replace the degraded LED module/lamp.
• Replace the underperforming isolating transformer.
• Clean the lens/optical surface if fouling is the confirmed cause.
• Clean and reseat a high-resistance primary connector.

Preventive Action

• Include periodic luminous intensity spot-checks against known-good reference fixtures in the PM programme.
• Track LED module lumen output trend over time to plan proactive replacement before it drops below tolerance.
• Include lens cleaning on a defined maintenance interval based on local environmental (dust/pollution) conditions.

Related References

SOP: SOP-EDG-09 (Light Output Verification Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46, IES LM-79 (LED photometric testing reference)

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge fixture (LED module), isolating transformer, and local/step selection wiring where fitted.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening any enclosure to check tap settings or driver configuration.
• An LED module driven above its rated current can overheat — handle with care immediately after de-energisation.

Diagnostic Procedure

1. ObservationConfirm the observation by comparing the reported fixture against multiple adjacent fixtures, not just one, to rule out the neighbouring-fixture-is-dim scenario.
2. MeasurementTake a luminous intensity reading on the reported fixture and compare against the expected value for the commanded intensity step per manufacturer photometric data.
3. MeasurementWith the circuit isolated, check the isolating transformer tap setting/wiring against the design step assignment for that fixture.
4. MeasurementIf an LED driver is fitted, measure driver output current and compare against the LED module's rated current.
5. DecisionTransformer tap mismatched to design → tap/wiring error. Driver output above rated LED current → driver fault. Correct module/tap but still bright → wrong-rated module fitted previously.
6. Fault LocationIsolate to the transformer tap/wiring, the LED driver, or an incorrectly specified LED module.
7. Root CauseConfirm against the original design intensity-step assignment and the correct part number for that fixture position.

Test Points

Root Cause Verification

After correction, re-measure luminous intensity output at the commanded step and confirm it matches manufacturer photometric data within tolerance, and matches adjacent fixtures.

Corrective Action

• Correct the isolating transformer tap setting to match the design intensity-step assignment.
• Replace a faulty LED driver with a correctly rated unit.
• Replace an incorrectly specified LED module with the correct part number.

Preventive Action

• Verify transformer tap settings against the design record whenever a transformer is replaced.
• Maintain a controlled parts list for LED conversion modules to prevent incorrect substitutions during maintenance.
• Include intensity-step verification in post-maintenance commissioning checks.

Related References

SOP: SOP-EDG-09 (Light Output Verification Procedure), SOP-EDG-10 (Isolating Transformer Tap Verification)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge fixture (LED module and driver), isolating transformer, and associated primary connections.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before tightening or inspecting any connector suspected of causing intermittent contact.
• Treat flicker accompanied by any unusual smell, heat, or discolouration as a potential fire risk — isolate immediately and inspect before re-energising.

Diagnostic Procedure

1. ObservationConfirm whether the flicker is isolated to a single fixture or observed across multiple fixtures on the same loop — the latter points toward a CCR-side cause (Division 01) rather than a local fixture fault.
2. MeasurementWith the fixture accessible and circuit isolated, gently flex/wiggle the primary connector and internal wiring (while de-energised) to check for looseness, then re-energise briefly under controlled conditions to observe if flicker correlates with connector position.
3. MeasurementIf an LED driver is fitted, check driver output for ripple/instability using a clamp meter with min/max hold or an oscilloscope if available.
4. MeasurementMeasure isolating transformer secondary output stability under load.
5. DecisionFlicker correlates with connector movement → loose connection. Driver output unstable independent of connections → driver fault. Transformer output unstable → transformer fault.
6. Fault LocationIsolate to the specific loose connector, the LED driver, or the isolating transformer.
7. Root CauseConfirm the failure mode — mechanical looseness, component degradation, or developing insulation fault — before closing out.

Test Points

Root Cause Verification

After corrective action, observe the fixture through at least one full intensity-step cycle and confirm stable, flicker-free operation with no recurrence over a sustained observation period.

Corrective Action

• Clean, tighten, or replace the loose primary connector.
• Re-terminate loose internal wiring connections.
• Replace a faulty LED driver.
• Replace a faulty isolating transformer.

Preventive Action

• Include connector torque checks in the periodic PM programme, particularly for fixtures in high-vibration areas (near touchdown zones).
• Track intermittent-fault fixtures across multiple reporting cycles to catch developing faults early.
• Use vibration-rated, locking-type connectors where specified for the fixture type.

Related References

SOP: SOP-EDG-03 (Single Fixture Fault Isolation), SOP-EDG-11 (Intermittent Fault Investigation)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 22 — Intermittent Fault Methodology; Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge fixture and isolating transformer, together with the primary series circuit connection and cable route to that fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before any physical inspection of a suspected intermittent connection.
• If water ingress is suspected as the intermittent trigger, do not attempt repeated re-energising to "test" the fault — investigate and dry the enclosure first.

Diagnostic Procedure

1. ObservationGather all available failure occurrence data — time of day, weather conditions, temperature, and any correlation with aircraft/vehicle movement — from maintenance logs or ALCMS event history.
2. MeasurementInstall a data logger on the affected fixture circuit to capture current/voltage behaviour over an extended period, ideally spanning the conditions under which the fault has previously occurred.
3. ObservationInspect the fixture and transformer for any sign of past moisture ingress (staining, corrosion, condensation residue) even if currently dry.
4. MeasurementPerform insulation resistance testing under both dry and (if safely possible) simulated damp conditions to check for a moisture-dependent leakage path.
5. DecisionFault correlates with temperature rise under load → thermal connection issue. Fault correlates with rain/high humidity → moisture ingress. No clear correlation → investigate driver/component-level intermittent fault.
6. Fault LocationIsolate to the specific connection, moisture entry point, or component identified through the correlation analysis.
7. Root CauseConfirm the root cause using the logged data and physical inspection findings together, rather than relying on a single test.

Test Points

Root Cause Verification

After corrective action, continue data-logging monitoring across at least one full cycle of the conditions previously associated with the fault (e.g., a full day/night thermal cycle, or a rain event) to confirm no recurrence.

Corrective Action

• Remake the thermally sensitive connection with a correctly rated, properly torqued terminal.
• Dry, inspect, and reseal the enclosure if moisture ingress is confirmed; replace any moisture-damaged components.
• Replace a developing-fault LED driver.
• Repair or replace damaged cable insulation.

Preventive Action

• Include thermal imaging of fixture/transformer connections in the periodic PM programme to catch marginal joints before they fail.
• Verify enclosure gasket and seal condition on a defined maintenance interval.
• Encourage systematic logging of intermittent fault conditions (time, weather) at first report to speed future correlation analysis.

Related References

SOP: SOP-EDG-11 (Intermittent Fault Investigation), SOP-EDG-07 (Splice Pit/Enclosure Inspection Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 22 — Intermittent Fault Methodology; Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Runway edge fixture LED module (or, in older installations, lamp with a coloured filter/lens), fixture lens/filter assembly.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before removing the lens/filter or LED module for inspection or replacement.

Diagnostic Procedure

1. ObservationConfirm the fixture position against the runway lighting design drawing to establish the correct required colour (white, or yellow in the applicable caution zone) for that specific location.
2. ObservationVisually compare the fixture against a known-good reference fixture of the same required colour, ideally at night.
3. MeasurementIf a colorimeter is available, measure chromaticity coordinates and compare against ICAO Annex 14 Appendix 2 chromaticity requirements for the relevant colour.
4. ObservationInspect the lens/filter for yellowing, cracking, or contamination that could shift the apparent colour.
5. DecisionCorrect module/filter for the position but colour still off → LED degradation or lens discolouration. Wrong module/filter type for the position → incorrect part fitted.
6. Fault LocationIsolate to the LED module, the lens/filter, or an incorrect part having been fitted at a previous maintenance visit.
7. Root CauseConfirm against the design record and, where available, chromaticity measurement, rather than visual judgement alone.

Test Points

Root Cause Verification

After correction, re-measure chromaticity (if equipment available) or perform a night-time visual comparison against a known-good reference, and confirm the fixture position matches the correct colour per the design drawing.

Corrective Action

• Replace a degraded/colour-shifted LED module with the correct-rated part.
• Replace a discoloured lens/filter.
• Correct a previously mis-fitted module or filter to the correct type for that position.

Preventive Action

• Maintain a strict controlled parts list distinguishing white versus yellow (and any other colour-coded) LED modules and filters to prevent mix-ups during maintenance.
• Include periodic chromaticity spot-checks in the PM programme, particularly for fixtures nearing their rated LED lifespan.
• Clearly mark caution-zone fixture positions on maintenance and as-built drawings.

Related References

SOP: SOP-EDG-09 (Light Output Verification Procedure), SOP-EDG-12 (Fixture Colour/Zone Verification)

Standards: ICAO Annex 14 Vol I & Appendix 2 (chromaticity), FAA AC 150/5340-30

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Runway Lighting Colour-Zone Plan

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Isolating transformer (multi-tap or auto-transformer type) and, where fitted, local step-sensing/LED driver electronics controlling that fixture's response to the series circuit current step.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before inspecting or correcting transformer tap wiring.

Diagnostic Procedure

1. ObservationCommand the CCR through each intensity step in turn and observe the affected fixture's response relative to known-good neighbouring fixtures at each step.
2. MeasurementWith the circuit isolated, check the isolating transformer tap wiring against the manufacturer's tap/current table for the design intensity-step assignment.
3. MeasurementIf a step-sensing LED driver is fitted, verify its current-sensing input and configuration against the manufacturer specification.
4. DecisionIf multiple fixtures across the loop show the identical wrong-step behaviour, escalate to Division 01 to rule out a CCR step-output fault before continuing fixture-level work. If isolated to this fixture, proceed with tap/driver correction.
5. Fault LocationIsolate to the specific transformer tap wiring error or driver configuration fault.
6. Root CauseConfirm the correct tap/configuration required and the point at which it was incorrectly set.

Test Points

Root Cause Verification

After correction, step the CCR through its full intensity range and confirm the fixture's output tracks correctly and matches known-good neighbouring fixtures at every step.

Corrective Action

• Rewire the isolating transformer tap to the correct terminal per the design intensity-step table.
• Reconfigure or replace a faulty step-sensing LED driver.
• Escalate to the applicable Division 01 CCR topic if the root cause is CCR-side.

Preventive Action

• Label transformer tap terminals clearly and verify against the design table during any tap-related maintenance.
• Include a full intensity-step verification check in post-maintenance commissioning for any fixture where the transformer or driver was disturbed.

Related References

SOP: SOP-EDG-10 (Isolating Transformer Tap Verification), SOP-EDG-09 (Light Output Verification Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Transformer Tap/Current Table

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Complete fixture optical assembly — LED module/lamp, reflector, lens, and prism (if fitted) — with electrical supply confirmed normal.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before internal inspection or cleaning of the optical assembly.

Diagnostic Procedure

1. MeasurementTake a luminous intensity reading at the manufacturer-specified test angle and distance, and compare against the fixture's rated photometric value for the commanded step.
2. ObservationConfirm electrical input to the fixture is normal (correct transformer output, correct driver current) before attributing the shortfall to the optical assembly — cross-reference EDG-165 if an electrical cause is suspected instead.
3. ObservationInspect the lens, reflector, and prism for dirt, discolouration, or physical displacement.
4. MeasurementClean the lens and re-measure luminous intensity to determine how much of the shortfall is attributable to surface contamination versus underlying LED/reflector degradation.
5. DecisionOutput restored to near-rated value after cleaning → optical fouling was the primary cause. Output remains low after cleaning → LED lumen depreciation or reflector degradation.
6. Fault LocationIsolate to lens contamination, reflector condition, prism alignment, or LED module ageing as the dominant contributor.
7. Root CauseConfirm against the manufacturer's L70 lumen-maintenance data where LED ageing is suspected as the primary cause.

Test Points

Root Cause Verification

After corrective action, re-measure luminous intensity output and confirm it meets the applicable minimum percentage of rated output per the site's maintenance standard.

Corrective Action

• Clean the lens, reflector, and prism assembly.
• Replace an LED module that has reached its L70 lumen-maintenance limit.
• Realign or reseat a displaced prism/lens.
• Replace an incorrectly specified lower-output LED module with the correct part.

Preventive Action

• Establish a defined lens-cleaning interval based on local environmental conditions (dust, rubber deposits, de-icing fluid exposure).
• Track LED module service hours against manufacturer L70 data to plan proactive replacement.
• Include periodic photometric spot-checks in the PM programme rather than relying on visual inspection alone.

Related References

SOP: SOP-EDG-09 (Light Output Verification Procedure), SOP-EDG-13 (Lens Cleaning Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46, IES LM-80/TM-21 (LED lumen maintenance reference)

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

LED module/array within the runway edge fixture, together with its mounting and interconnection to the driver or transformer secondary.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before removing the LED module for inspection or bench testing.
• Allow the module and heat sink to cool before handling, as LED modules can run hot even under normal operation.

Diagnostic Procedure

1. ObservationConfirm the transformer secondary output and/or LED driver output are within specification, isolating the fault to the LED module itself rather than its supply.
2. ObservationVisually inspect the removed module for discolouration, burn marks, corrosion, or physical damage.
3. MeasurementBench-test the module on a known-good driver/test jig at rated current to confirm the failure and, where the module has multiple strings, identify how many strings remain functional.
4. ObservationInspect the heat sink and thermal interface for blockage, degraded thermal compound, or damage that could indicate an overheating root cause.
5. DecisionConfirmed failed module with no external cause found → LED end-of-life/manufacturing defect. Corrosion present → moisture ingress root cause. Overheating signs present → thermal management root cause.
6. Fault LocationIsolate to the LED module as the failed component, and identify any contributing external cause (moisture, overheating, overdrive).
7. Root CauseConfirm whether the failure is a standalone component failure or symptomatic of a broader fixture-level issue requiring additional corrective action.

Test Points

Root Cause Verification

After replacement, confirm the new module operates correctly at all intensity steps and, where an external cause (overheating, overdrive) was identified, confirm that cause has also been corrected before closing out.

Corrective Action

• Replace the failed LED module with the correct-rated part.
• Correct an overdriving LED driver configuration if identified as a contributing cause.
• Restore thermal management — clean heat sink, replace thermal interface material — if overheating is confirmed as a contributing cause.
• Dry and inspect the fixture for further moisture-related damage if corrosion is found.

Preventive Action

• Track LED module failure rates by fixture position/environment to identify problem areas (e.g., high-moisture or high-vibration zones).
• Verify driver current settings match the LED module rating whenever either component is replaced.
• Include heat sink/thermal interface condition checks in periodic PM.

Related References

SOP: SOP-EDG-14 (LED Module Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46, IES LM-80/TM-21

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Sealed-beam filament lamp (e.g., PAR56, 6.6A/45W or 6.6A/200W series-rated) and its lampholder/socket within the fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before replacing the lamp.
• Allow the lamp to cool fully before handling — sealed-beam lamps retain heat and can cause burns.
• Handle new sealed-beam lamps by the rim, avoiding skin contact with the glass, to prevent oil deposits that can cause premature failure or breakage under thermal cycling.

Diagnostic Procedure

1. ObservationConfirm the isolating transformer secondary output is within specification, isolating the fault to the lamp itself.
2. ObservationVisually inspect the lamp for a visibly blown/broken filament, cracked lens, or discolouration.
3. MeasurementTest lamp continuity directly with a continuity tester if the filament condition cannot be confirmed visually.
4. ObservationInspect the lampholder/socket contacts for corrosion, arcing marks, or looseness.
5. DecisionLamp confirmed open-circuit with a sound socket → standard lamp failure, replace lamp. Socket shows arcing/corrosion → contact fault also requires correction.
6. Fault LocationIsolate to the lamp itself or, additionally, to a faulty lampholder/socket.
7. Root CauseNote the lamp's installed/service duration if recorded, to distinguish normal end-of-life failure from premature failure warranting further investigation (e.g., voltage surge, vibration).

Test Points

Root Cause Verification

After replacement, confirm the new lamp illuminates correctly at all intensity steps and that the lampholder makes secure, low-resistance contact.

Corrective Action

• Replace the lamp with the correct wattage/type-rated spare.
• Clean or replace a corroded/arced lampholder/socket.
• Investigate and correct the cause of premature failure (e.g., voltage regulation, vibration mounting) if the lamp failed well before its rated service life.

Preventive Action

• Track lamp service hours per fixture and replace proactively on a group-relamping basis where practical, rather than only on failure.
• Inspect lampholder contacts during scheduled relamping.
• Consider LED conversion for fixtures with a history of repeated premature lamp failure due to vibration, where approved by the applicable standard.

Related References

SOP: SOP-EDG-15 (Lamp Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

LED driver (constant-current or series-circuit-current-sensing type) within the fixture, converting the series circuit primary current into the correct drive current for the LED module.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before removing or replacing the driver.
• Allow driver capacitors to discharge before handling — treat as potentially energised for a short period after isolation per manufacturer guidance.

Diagnostic Procedure

1. ObservationConfirm isolating transformer secondary output (or series circuit current at the driver input) is within specification, isolating the fault to the driver itself.
2. MeasurementTest the driver output using a known-good LED module or bench load, to confirm whether the driver is producing no output, unstable output, or incorrect output current.
3. ObservationInspect the driver for physical signs of failure — bulging/leaking capacitors, burn marks, or corrosion.
4. MeasurementSubstitute a known-good spare driver with the original (suspect) LED module to confirm the fault follows the driver rather than the module.
5. DecisionFault follows the driver on substitution → confirmed driver failure. Physical damage/corrosion present → identify contributing environmental cause. No physical signs and isolated occurrence → standard component failure/end of life.
6. Fault LocationIsolate to the LED driver as the failed component.
7. Root CauseDetermine whether the failure is a standalone component failure, or attributable to a surge event, overheating, or moisture ingress requiring additional corrective action.

Test Points

Root Cause Verification

After replacement, confirm the fixture operates correctly and stably through a full intensity-step cycle, and confirm any identified contributing cause (surge, overheating, moisture) has also been addressed.

Corrective Action

• Replace the failed LED driver with the correct-rated part.
• Install or verify surge protection on the series circuit if a transient event is confirmed as a contributing cause.
• Improve driver ventilation/heat dissipation if overheating is confirmed as a contributing cause.
• Dry and reseal the enclosure if moisture ingress is confirmed.

Preventive Action

• Track driver failure rates and service life by fixture location/environment to identify problem areas.
• Include surge protection device condition checks in the PM programme where fitted.
• Verify driver enclosure seals during scheduled maintenance in high-moisture areas.

Related References

SOP: SOP-EDG-16 (LED Driver Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Lampholder/socket or LED module mounting terminal within the fixture, and its connection to the transformer secondary or driver output wiring.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before handling the lampholder/socket or terminal connection.
• Allow the lamp/module to cool before handling.

Diagnostic Procedure

1. ObservationWith power isolated, physically inspect the lamp/module seating in its holder — confirm it is fully inserted/locked per the manufacturer's fitting method.
2. MeasurementGently test for movement at the terminal screws/spring contacts; a connection that moves under light finger pressure indicates looseness.
3. ObservationInspect contact surfaces for corrosion, pitting, or discolouration from previous arcing at a loose connection.
4. MeasurementAfter cleaning and correctly re-seating/tightening, measure continuity/resistance across the connection to confirm a low-resistance, stable contact.
5. DecisionSimple looseness with clean contacts → re-seat and torque correctly. Corroded/pitted contacts present → clean or replace the holder/terminal in addition to re-seating.
6. Fault LocationIsolate to the specific loose terminal or improperly seated lamp/module.
7. Root CauseConfirm whether the looseness is an isolated installation/maintenance issue or a symptom of a worn/undersized holder requiring replacement.

Test Points

Root Cause Verification

After re-seating and securing the connection, confirm stable operation through a full intensity-step cycle with no recurrence of flicker or intermittent behaviour, and re-check torque/seating at a short-interval follow-up if the original cause was unclear.

Corrective Action

• Re-seat the lamp/module fully and correctly per the manufacturer fitting method.
• Clean corroded contact surfaces with an appropriate electrical contact cleaner.
• Tighten terminal screws to the correct torque specification.
• Replace a worn or damaged lampholder/socket that no longer grips securely.

Preventive Action

• Include correct lamp/module seating verification as a mandatory step in the relamping/module-replacement work instruction.
• Include terminal torque checks in the periodic PM programme, particularly for fixtures in high-vibration locations.
• Train maintenance staff on the correct seating/locking method for the specific fixture type in use.

Related References

SOP: SOP-EDG-14 (LED Module Replacement Procedure), SOP-EDG-15 (Lamp Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Internal wiring, terminal blocks, and splice connections within the runway edge fixture housing, between the cable entry gland and the lamp/module/driver.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture housing or handling any internal wiring.
• Verify zero energy with a proven meter before touching terminals, even after isolation.

Diagnostic Procedure

1. ObservationWith power isolated, open the fixture housing and visually inspect all internal terminal blocks, ring lugs, and splices for looseness, discolouration, or corrosion.
2. MeasurementGently test each terminal for movement under light finger pressure; a connection that shifts indicates looseness even if visually intact.
3. MeasurementMeasure contact resistance across suspect terminals where practical, comparing against an adjacent known-good connection.
4. ObservationCheck ring lug/ferrule sizing against the conductor gauge to confirm correct fit.
5. DecisionSimple looseness with no corrosion → re-torque to specification. Corrosion or discolouration present → clean or replace the terminal/lug in addition to re-torquing.
6. Fault LocationIsolate to the specific loose terminal, splice, or incorrectly sized lug.
7. Root CauseConfirm whether the cause is an installation/torque issue, vibration, or a developing corrosion problem, to guide the appropriate preventive action.

Test Points

Root Cause Verification

After re-terminating, confirm stable operation through a full intensity-step cycle and re-check torque at a short-interval follow-up if the original cause of loosening was not conclusively identified.

Corrective Action

• Re-torque all internal terminals to the manufacturer-specified value.
• Replace an incorrectly sized ring lug/ferrule with a correctly sized one, and re-crimp.
• Clean corroded terminal surfaces before re-terminating.
• Replace a damaged terminal block if it can no longer hold a secure connection.

Preventive Action

• Include internal terminal torque checks in the periodic PM programme, particularly for fixtures in high-vibration locations.
• Use spring-loaded or vibration-resistant terminal types where specified for the fixture type.
• Verify correct ring lug/ferrule sizing as a standard step in any internal wiring work.

Related References

SOP: SOP-EDG-17 (Internal Wiring Inspection & Torque Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 22 — Intermittent Fault Methodology; Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture housing, cable gland/entry, gasket/seal system, and drainage provision (if fitted) of the runway edge fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening a fixture found or suspected to contain water — do not energise a wet fixture.
• Treat all internal components as contaminated until dried and insulation-tested; water ingress significantly increases shock/short-circuit risk.
• Allow full drying and confirm insulation resistance is within acceptable limits before considering re-energisation.

Diagnostic Procedure

1. ObservationWith power isolated, open the fixture and visually confirm the presence and approximate volume of standing water.
2. ObservationInspect the gasket, cable gland, housing joints, and lens for the specific entry point — look for a visible water track or staining leading from the entry point.
3. MeasurementRemove the water and dry the fixture thoroughly before performing insulation resistance testing on all internal wiring and components.
4. ObservationCheck for a drainage provision (weep hole or drain channel) and confirm whether it is present, clear, and functioning, or blocked/missing.
5. DecisionClear entry point identified (gasket/gland/crack) → seal fault, proceed to seal/component repair. No clear entry point but drainage blocked/absent → drainage design/blockage issue.
6. Fault LocationIsolate to the specific gasket, gland, crack, or drainage deficiency responsible for the water accumulation.
7. Root CauseConfirm the entry mechanism and, separately, whether inadequate drainage contributed to accumulation even if the initial ingress volume was otherwise minor.

Test Points

Root Cause Verification

After repair and thorough drying, confirm insulation resistance across all internal circuits meets the minimum acceptable value before re-energising, and re-inspect after the next significant rainfall event to confirm no recurrence.

Corrective Action

• Replace the failed or missing gasket.
• Repair or replace a damaged/incorrectly fitted cable gland.
• Clear a blocked drainage path or add a drainage provision where the design allows.
• Repair or replace a cracked housing/lens.
• Thoroughly dry and insulation-test the fixture before re-energising.

Preventive Action

• Include gasket, gland, and drainage condition checks in the periodic PM programme.
• Inspect fixtures in known low-lying/poor-drainage areas more frequently, particularly after heavy rainfall.
• Replace gaskets proactively on a defined service interval rather than only on failure.

Related References

SOP: SOP-EDG-18 (Fixture Water Ingress Response Procedure), SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Sealing/Gasket Detail

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture housing, gasket/seal system, and any fitted breather/vent provision of the runway edge fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture for inspection.
• Treat elevated internal moisture as a precursor to insulation degradation — verify insulation resistance before returning the fixture to service.

Diagnostic Procedure

1. ObservationWith power isolated, open the fixture and assess the degree of internal dampness/haze on surfaces, and check for any odour indicative of prolonged moisture presence.
2. MeasurementPerform insulation resistance testing on internal wiring/components to confirm moisture has not yet caused measurable insulation degradation.
3. ObservationInspect the gasket compression and condition around the full perimeter of the housing joint, looking for uneven compression or hardened/cracked gasket material.
4. ObservationIf a desiccant/breather element is fitted, check its condition (colour-indicating desiccant, if used, typically changes colour when saturated).
5. DecisionInsulation resistance within acceptable limits, gasket marginal → early-stage seal degradation, replace gasket proactively. Insulation resistance reduced → treat with the same urgency as EDG-177 and dry fully before re-energising.
6. Fault LocationIsolate to the gasket condition, seal compression, or a depleted desiccant/breather element as the source of internal humidity.
7. Root CauseConfirm whether this is an early-stage seal issue to be corrected proactively, or has already progressed to a level requiring the fuller response used for EDG-177.

Test Points

Root Cause Verification

After gasket replacement/correction, re-inspect the fixture at the next scheduled interval to confirm internal humidity has returned to a normal, dry condition with no recurrence of haze or dampness.

Corrective Action

• Replace the gasket to restore a full, even seal.
• Replace a depleted desiccant/breather element where fitted.
• Dry the fixture interior before closing up.

Preventive Action

• Include gasket compression checks (not just presence/absence) in the periodic PM programme, since a gasket can be present but no longer sealing effectively.
• Replace gaskets proactively on a defined service interval based on local climate severity.
• Monitor and replace desiccant/breather elements on a defined schedule where fitted.

Related References

SOP: SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Sealing/Gasket Detail

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture lens (inner surface), housing internal surfaces, and any fitted breather/vent provision.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture for inspection or intervention.
• Condensation directly on live components presents a shock/short risk — do not assume light misting is harmless without inspecting proximity to energised parts.

Diagnostic Procedure

1. ObservationNote the time and conditions under which condensation was observed (e.g., cold morning, after rain, following recent maintenance) to help distinguish normal thermal-cycling condensation from a seal-related cause.
2. ObservationWith power isolated, open the fixture and inspect the gasket seal condition and compression, as for EDG-178, to rule out an underlying seal fault before attributing the condensation to normal thermal cycling alone.
3. MeasurementPerform insulation resistance testing to confirm the condensation has not caused any measurable insulation degradation.
4. ObservationIf the fixture was recently opened for maintenance, review whether it may have been closed up in humid conditions or without adequate drying time, which would explain isolated condensation without an ongoing seal fault.
5. DecisionGasket sound, condensation explained by recent maintenance/thermal cycling → isolated occurrence, dry and reseal. Gasket marginal or condensation recurring without a clear one-off cause → treat as early-stage seal degradation per EDG-178.
6. Fault LocationIsolate to normal thermal-cycling behaviour in an otherwise sound fixture, a one-off closure-in-humid-conditions event, or an underlying seal issue.
7. Root CauseConfirm through insulation resistance testing and gasket inspection whether further corrective action beyond drying is required.

Test Points

Root Cause Verification

After drying and resealing, monitor the fixture over the next few thermal cycles (day/night transitions) to confirm condensation does not recur; recurrence indicates the underlying cause was a seal fault rather than an isolated event.

Corrective Action

• Fully dry the fixture interior before resealing.
• Reseal the fixture ensuring the gasket is correctly seated and compressed.
• Where the design permits, install or replace a desiccant/breather element to manage internal humidity.

Preventive Action

• Ensure fixtures are only closed up when dry and, where practical, in low-humidity conditions during maintenance.
• Include a moisture/condensation check as a specific item in the periodic PM inspection checklist.
• Track fixtures with recurring condensation reports separately, as they may indicate a developing seal issue rather than normal behaviour.

Related References

SOP: SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture lens assembly (glass or polycarbonate), including its retaining ring/frame and seal against the fixture housing.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before removing a broken lens — sharp edges and potential exposure to live components underneath.
• Wear cut-resistant gloves when handling broken glass/polycarbonate lens fragments.
• Inspect for and remove all loose fragments from inside the fixture before reassembly to prevent future rattling/damage.

Diagnostic Procedure

1. ObservationDocument the extent and pattern of the crack/break, and inspect the surrounding area for evidence of the cause (impact mark, FOD nearby, mower proximity).
2. ObservationWith power isolated, remove the lens and inspect the internal components (LED module/lamp, reflector) for any damage or contamination from the broken lens or resulting exposure.
3. ObservationInspect the lens retaining ring and housing seating surface for damage or incorrect fitment that may have contributed to the failure.
4. DecisionClear impact/FOD cause identified → replace lens, no further investigation needed beyond confirming internal components are undamaged. No clear external cause, retaining ring over-torqued or seating surface uneven → investigate installation-induced stress as a contributing cause.
5. Fault LocationIsolate to the specific cause of breakage where determinable, and confirm the condition of internal components exposed by the broken lens.
6. Root CauseConfirm whether the cause was external damage (isolated event) or an installation/design factor likely to recur.

Test Points

Root Cause Verification

After lens replacement, confirm the new lens is correctly seated, the retaining ring is torqued to specification, and the seal is intact by insulation-resistance testing following the next rainfall or a controlled water-spray check where practical.

Corrective Action

• Replace the broken lens with the correct part number.
• Replace the lens gasket/seal at the same time as lens replacement.
• Clean and inspect internal components exposed by the break before closing up.
• Correct retaining ring torque to the manufacturer specification.

Preventive Action

• Maintain adequate clearance/marking around fixtures in mowing/vehicle-access areas.
• Include lens condition (cracks, chips, UV degradation) as a specific item in routine visual inspection.
• Torque-check lens retaining rings to specification during any maintenance that involves lens removal.

Related References

SOP: SOP-EDG-20 (Lens Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Prism element and its mounting/retention within the fixture optical assembly, positioned between the LED module/lamp and the outer lens.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before accessing the internal optical assembly.
• Handle prism fragments carefully — sharp edges possible on broken polycarbonate/glass elements.

Diagnostic Procedure

1. ObservationWith power isolated, remove the lens and inspect the prism for the extent and location of the damage.
2. ObservationCheck the LED module/lamp position and heat sink condition to assess whether excess heat could have contributed to thermal stress damage.
3. ObservationInspect the prism retention/mounting for correct fit, ruling out a mounting fault that could have caused mechanical stress on the prism.
4. DecisionClear physical impact damage → isolated event, replace prism. No impact evidence, heat/mounting-related signs present → investigate contributing thermal or mounting cause in addition to replacement.
5. Fault LocationIsolate to impact damage, thermal stress, or a mounting-induced stress as the cause.
6. Root CauseConfirm whether the cause is isolated or likely to recur with the replacement prism unless the contributing factor is also corrected.

Test Points

Root Cause Verification

After replacement, verify the fixture produces the correct beam pattern for its position type (compare against the manufacturer photometric/beam pattern reference or a known-good fixture) before returning to service.

Corrective Action

• Replace the damaged prism with the correct part number.
• Correct the prism mounting/retention if a fit issue is identified.
• Address a thermal management issue (heat sink, driver current) if confirmed as a contributing cause.

Preventive Action

• Handle internal optical components with care during any maintenance requiring lens/prism removal — use a clean, padded work surface.
• Include prism condition in the internal inspection checklist whenever the fixture is opened for other work.

Related References

SOP: SOP-EDG-21 (Prism Replacement & Alignment Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Beam Pattern/Photometric Reference

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Prism element and its mounting/retention clips or frame within the fixture optical assembly.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before accessing the internal optical assembly.

Diagnostic Procedure

1. ObservationWith power isolated, remove the lens and observe the prism position relative to its correct mounted location and orientation per the technical manual.
2. ObservationInspect the retention clips/frame for damage, wear, or incorrect engagement.
3. ObservationConfirm the prism part number and profile match what is specified for that fixture type/position.
4. DecisionRetention clips sound, simply not engaged → re-seat and confirm engagement. Retention clips damaged/worn → replace before re-seating. Wrong part number fitted → replace with correct part.
5. Fault LocationIsolate to a simple mis-seating, a damaged retention system, or an incorrect part having been fitted previously.
6. Root CauseConfirm the prism will remain securely seated by testing engagement before closing up the fixture.

Test Points

Root Cause Verification

After re-seating (or replacing the retention system/prism), confirm the fixture produces the correct beam pattern and that the prism remains securely seated when the fixture is gently handled.

Corrective Action

• Re-seat the prism fully into its correct mounted position and orientation.
• Replace damaged or worn retention clips/frame.
• Replace an incorrect prism part with the correct type for that fixture position.

Preventive Action

• Confirm full prism engagement as a mandatory checklist item whenever a fixture is opened for lens/prism-related work.
• Maintain a controlled parts list for prism types to prevent incorrect substitutions.

Related References

SOP: SOP-EDG-21 (Prism Replacement & Alignment Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Beam Pattern/Photometric Reference

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture lens outer surface.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before cleaning if the cleaning procedure requires close contact with the fixture (recommended even for exterior-only cleaning to prevent accidental contact with energised parts).
• Use only cleaning agents approved for the lens material (glass or polycarbonate) — some solvents can craze or degrade polycarbonate lenses.
• Follow airside safety and FOD-control procedures during cleaning, ensuring no debris or cleaning material is left on the movement area.

Diagnostic Procedure

1. ObservationVisually assess the type and extent of contamination (dust, rubber, fluid residue) to select the appropriate cleaning approach.
2. MeasurementIf a light output meter is available, take a luminous intensity reading before cleaning to quantify the impact of the contamination.
3. ObservationClean the lens using the approved method and solution for the contamination type and lens material.
4. MeasurementRe-measure luminous intensity output after cleaning, if equipment is available, to confirm the improvement and rule out an underlying component-level cause (cross-reference EDG-171 if output remains low after cleaning).
5. DecisionOutput restored to near-rated value after cleaning → contamination was the primary cause, closed as a cleaning action. Output remains low after cleaning → investigate further per EDG-171.
6. Fault LocationConfirm the lens surface as the sole cause, or identify a residual underlying cause requiring further investigation.

Test Points

Root Cause Verification

After cleaning, visually confirm the lens is clear of contamination and, where measured, confirm luminous intensity output is restored to an acceptable value relative to a known-good reference fixture.

Corrective Action

• Clean the lens using an approved method and solution for the contamination type and lens material.

Preventive Action

• Establish a defined lens-cleaning interval based on local environmental conditions, increasing frequency near touchdown zones or de-icing pad areas.
• Include lens condition as a specific visual-inspection checklist item during routine and periodic PM.
• Coordinate cleaning schedules with airfield rubber-removal and de-icing operations where practical.

Related References

SOP: SOP-EDG-13 (Lens Cleaning Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Internal reflector, prism inner surface, and lens inner surface within the fixture optical assembly.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before accessing internal optical surfaces.
• Use only cleaning agents confirmed compatible with reflector coatings — some solvents can strip or dull reflective coatings, permanently reducing reflector performance.

Diagnostic Procedure

1. ObservationWith power isolated and the lens removed, inspect the reflector, prism inner surface, and lens inner surface for contamination, discolouration, or coating degradation.
2. ObservationDistinguish removable surface contamination (dust, residue film) from a permanently degraded/discoloured reflector coating by attempting a light, approved cleaning test on a small area.
3. MeasurementWhere a light output meter is available, measure before and after cleaning to quantify the contribution of internal optical contamination separately from any electrical cause.
4. ObservationIf moisture-related residue is suspected, check for a history of EDG-178/179 reports on this fixture and inspect the gasket/seal condition.
5. DecisionContamination removable by cleaning → internal cleaning resolves the issue. Coating degraded/discoloured and not improved by cleaning → reflector component-level replacement required.
6. Fault LocationIsolate to removable internal contamination versus underlying reflector coating degradation.
7. Root CauseWhere moisture residue is confirmed as the contamination source, address the underlying seal issue (EDG-177/178/179) in addition to cleaning, to prevent recurrence.

Test Points

Root Cause Verification

After cleaning or reflector replacement, re-measure luminous intensity output and confirm it is restored to an acceptable value relative to a known-good reference fixture, and address any underlying seal issue identified.

Corrective Action

• Clean the internal reflector, prism, and lens inner surfaces using an approved, coating-compatible method.
• Replace the reflector if its coating is confirmed degraded rather than simply contaminated.
• Address the underlying seal/moisture-ingress cause if internal contamination is traced to EDG-177/178/179.

Preventive Action

• Include internal optical surface condition as a specific check whenever the fixture is opened for any other maintenance.
• Correct any underlying seal deficiency promptly to prevent internal contamination from recurring.
• Track fixtures with recurring internal contamination to identify a systemic seal or component quality issue.

Related References

SOP: SOP-EDG-13 (Lens Cleaning Procedure), SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Lens/housing gasket (typically silicone or EPDM rubber) and its seating groove within the fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture for gasket replacement.
• Inspect for and address any moisture or water ingress (EDG-177/178/179) that may have occurred as a result of the broken gasket before closing up the fixture again.

Diagnostic Procedure

1. ObservationWith power isolated, remove the lens/cover and inspect the gasket for the extent and pattern of the damage — full-perimeter perishing versus a localised tear.
2. ObservationInspect the gasket seating groove for damage, debris, or an incorrect gasket profile that may have contributed to the failure.
3. ObservationCheck for evidence of moisture ingress inside the fixture resulting from the broken gasket, per EDG-177/178/179 as applicable.
4. DecisionAge/UV-related full-perimeter perishing → standard end-of-service-life replacement. Localised tear from a specific installation event → correct the installation practice in addition to replacement. Wrong part number found → replace with correct part.
5. Fault LocationIsolate to gasket age, installation damage, chemical attack, or an incorrect part as the cause.
6. Root CauseConfirm the cause to guide the appropriate preventive action, particularly if a wrong part or installation practice issue is found.

Test Points

Root Cause Verification

After replacement, confirm even gasket compression around the full perimeter, correct retaining torque, and — following the next rainfall or a controlled water-spray check where practical — confirm no water ingress.

Corrective Action

• Replace the gasket with the correct part number.
• Clean and, if necessary, lightly recondition the gasket seating groove before fitting the new gasket.
• Correct retaining ring/housing bolt torque to the manufacturer specification.
• Address any moisture ingress found inside the fixture as a result of the failed gasket.

Preventive Action

• Replace gaskets proactively on a defined service interval based on local climate/UV exposure severity, rather than only on failure.
• Use only cleaning agents confirmed compatible with the gasket material.
• Maintain a controlled parts list for gasket types to prevent incorrect substitutions.

Related References

SOP: SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Sealing/Gasket Detail

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Lens/housing gasket and its compression/retention system (retaining ring, housing bolts, clips) within the fixture.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before opening the fixture for inspection or gasket work.

Diagnostic Procedure

1. ObservationWith power isolated, remove the lens/cover and inspect the gasket for visible compression marks around the perimeter — an uneven compression pattern indicates uneven sealing pressure.
2. MeasurementCheck retaining ring/housing bolt torque at multiple points around the perimeter, comparing against the manufacturer specification and looking for inconsistency.
3. ObservationInspect the gasket seating groove for debris, old sealant, or corrosion preventing full contact.
4. ObservationInspect the housing/lens frame for warping or distortion that could prevent even gasket contact even with correct torque applied.
5. DecisionUneven/incorrect torque found → correct torque application. Groove contamination found → clean groove and re-seat. Housing/frame warped → component-level repair or replacement required beyond gasket work alone.
6. Fault LocationIsolate to torque application, groove contamination, or housing/frame distortion as the cause of the leak despite an intact gasket.
7. Root CauseConfirm the specific mechanical cause preventing effective sealing, since simply replacing the gasket without addressing this cause will not resolve a leak of this type.

Test Points

Root Cause Verification

After correction, confirm even, correctly torqued compression around the full perimeter and, following the next rainfall or a controlled water-spray check where practical, confirm no further water ingress.

Corrective Action

• Correct retaining ring/housing bolt torque to an even, specified value around the full perimeter.
• Clean the gasket seating groove of debris, old sealant, or corrosion before re-seating.
• Replace a warped or distorted housing/lens frame component.
• Replace the gasket with the correct thickness/profile if an undersized part is found.

Preventive Action

• Use a torque sequence (e.g., star pattern) when tightening retaining rings/bolts to achieve even gasket compression.
• Include seating groove cleanliness as a specific step in the gasket replacement work instruction.
• Inspect housing/lens frames for distortion whenever recurring leak issues are reported on a specific fixture despite gasket replacement.

Related References

SOP: SOP-EDG-19 (Gasket & Seal Replacement Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Sealing/Gasket Detail

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture housing/body structure (elevated fixture riser/base or inset fixture body/frame).

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before handling a damaged fixture — structural damage may have also compromised internal wiring insulation.
• Treat a damaged elevated fixture as a FOD and safety hazard — assess whether immediate removal/temporary marking is required pending repair, per site safety procedure.
• For inset fixtures with pavement-level damage, assess and coordinate any pavement surface hazard with airfield operations before leaving the location.

Diagnostic Procedure

1. ObservationDocument the extent, location, and likely cause of the body damage, including any associated pavement or surrounding surface damage.
2. ObservationWith power isolated, inspect internal wiring and components for damage or displacement resulting from the impact, not just the visible external damage.
3. MeasurementPerform insulation resistance testing on the fixture's internal wiring to rule out damage-induced insulation degradation even where internal components appear undamaged.
4. ObservationFor inset fixtures, check frame flatness/level against the surrounding pavement to confirm correct seating is still achievable, or whether frame replacement is required.
5. DecisionBody damage cosmetic/minor with sound internals and insulation → assess for repair versus replacement based on structural integrity. Body damage affecting fixture mounting, sealing, or internal component safety → replace the fixture body/complete assembly.
6. Fault LocationIsolate to the specific damaged component — body/housing, mounting frame, or riser — and confirm whether the damage is repairable or requires replacement.
7. Root CauseConfirm and record the likely cause to inform relevant preventive/coordination action (e.g., with mowing contractors or snow-removal operations).

Test Points

Root Cause Verification

After repair or replacement, confirm the fixture is securely mounted/seated, insulation resistance is within acceptable limits, and the fixture operates correctly through a full intensity-step cycle before returning to service.

Corrective Action

• Replace the damaged fixture body/housing or complete fixture assembly.
• Repair minor cosmetic damage where structural integrity and sealing are confirmed unaffected.
• Replace damaged internal wiring identified during inspection.
• Re-level/re-seat an inset fixture frame where pavement seating has been affected.

Preventive Action

• Coordinate fixture location awareness with mowing, snow-removal, and ground-equipment operators to reduce impact risk.
• Include structural condition as a specific item in routine visual inspection, particularly after any known ground equipment incident.
• Consider more impact-resistant fixture types for locations with a history of repeated body damage.

Related References

SOP: SOP-EDG-22 (Fixture Body/Housing Replacement Procedure), SOP-EDG-23 (Damage Reporting & FOD Hazard Response)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture housing, mounting hardware, internal metallic brackets/terminals, and (for inset fixtures) the frame/base assembly.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before working on a corroded fixture, particularly where corrosion is near electrical terminals or wiring.
• Use appropriate PPE when removing corrosion products, which may include fine particulates.

Diagnostic Procedure

1. ObservationAssess the extent and location of corrosion — surface-only, or affecting structural sections, mounting hardware, or electrical terminals.
2. ObservationIdentify the fixing/mounting hardware material and check for evidence of dissimilar-metal contact that could indicate galvanic corrosion.
3. MeasurementWhere corrosion is near electrical terminals, measure contact resistance/insulation resistance to confirm whether the corrosion has affected electrical performance.
4. ObservationAssess whether corrosion is consistent with the general environmental exposure at this location (e.g., near a de-icing pad, coastal airfield) or appears localised/premature.
5. DecisionSurface corrosion only, no structural/electrical impact → clean and treat. Corrosion affecting structural integrity or electrical terminals → component/hardware replacement required in addition to treatment.
6. Fault LocationIsolate to the specific components affected and the level of severity — surface, structural, or electrical.
7. Root CauseConfirm the corrosion mechanism (moisture, de-icing fluid, galvanic, coating damage) to guide the appropriate preventive/material selection response.

Test Points

Root Cause Verification

After treatment/replacement, confirm mechanical integrity of the affected component, and confirm electrical contact resistance/insulation resistance is within acceptable limits where terminals were involved.

Corrective Action

• Remove surface corrosion and apply an approved anti-corrosion treatment/coating.
• Replace structurally compromised housing or mounting components.
• Replace corroded electrical terminals/hardware and re-terminate.
• Replace dissimilar-metal fixing hardware with a compatible material grade.

Preventive Action

• Specify corrosion-resistant materials/coatings appropriate to the local environment (coastal, de-icing exposure) for fixture and hardware replacement.
• Include corrosion assessment as a specific PM checklist item, particularly for fixtures in known high-exposure areas.
• Address the underlying moisture-ingress cause (EDG-177/178/179) promptly to limit ongoing corrosion risk.

Related References

SOP: SOP-EDG-24 (Corrosion Assessment & Treatment Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

LED module/driver, lamp (legacy fixtures), heat sink/thermal management system, and fixture housing.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before handling a fixture confirmed or suspected to be overheating, and allow it to cool before close physical inspection.
• Treat a fixture showing discolouration/burning odour as a potential fire risk — isolate immediately and do not re-energise until fully investigated.

Diagnostic Procedure

1. ObservationTake a surface/component temperature reading (thermal camera or infrared thermometer) and compare against a known-good reference fixture under the same operating and ambient conditions.
2. ObservationWith power isolated and the fixture cooled, inspect the heat sink for blockage, debris, or physical damage.
3. ObservationInspect the thermal interface between the LED module and heat sink for degradation, gaps, or incorrect application.
4. MeasurementMeasure LED driver output current and compare against the LED module's rated current to rule out overdrive as a contributing cause.
5. DecisionHeat sink blocked/degraded thermal interface found → thermal management fault, correct directly. Driver output above rated current → driver configuration/fault, correct per EDG-174. Heat sink and driver both normal → investigate ambient/environmental contribution.
6. Fault LocationIsolate to heat sink condition, thermal interface, driver overdrive, or ambient/environmental factors.
7. Root CauseConfirm the dominant contributing factor(s) — overheating is frequently multi-causal (e.g., a marginal thermal interface combined with high ambient temperature).

Test Points

Root Cause Verification

After corrective action, re-measure temperature under representative operating conditions (including peak ambient temperature if practical) and confirm the fixture runs within the manufacturer's rated operating temperature range.

Corrective Action

• Clean and clear the heat sink and ventilation path of debris/blockage.
• Replace degraded thermal interface material with correctly applied, correctly rated material.
• Correct LED driver configuration to the module's rated current.
• Consider a fixture/location-specific mitigation (e.g., shading, alternate part rating) where ambient conditions are a significant contributing factor.

Preventive Action

• Include heat sink/ventilation path condition in the periodic PM programme.
• Verify driver current settings match the LED module rating whenever either is replaced.
• Track fixtures with recurring overheating reports to identify a location-specific or batch-related thermal issue.

Related References

SOP: SOP-EDG-16 (LED Driver Replacement Procedure), SOP-EDG-25 (Thermal Inspection Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)

Equipment / System

Fixture mounting/base (elevated fixture riser and frangible coupling, or inset fixture frame/leveling system) and its aiming/orientation reference.

Possible Causes

Required Tools

Safety Precautions

• De-energise and LOTO before adjusting or working on the fixture mounting.
• For elevated fixtures on a frangible coupling, inspect the coupling condition before applying force to straighten/realign the fixture — a partially sheared coupling may fail completely under load.
• Obtain airside/runway access clearance before working at the fixture location.

Diagnostic Procedure

1. ObservationVisually assess the fixture's tilt/rotation relative to adjacent, correctly aligned fixtures and the runway centreline.
2. MeasurementUse an inclinometer/level and the design aiming diagram to quantify the deviation from the specified elevation and azimuth angle for that fixture position.
3. ObservationFor elevated fixtures, inspect the frangible coupling for damage or partial shearing before attempting realignment.
4. ObservationFor inset fixtures, check the surrounding pavement/frame level for settlement or heave that may be the underlying cause rather than a simple loose fixing.
5. DecisionFrangible coupling intact, fixing loose → re-align and re-torque. Frangible coupling damaged/partially sheared → replace coupling as part of the correction. Ground/pavement settlement confirmed → broader pavement/foundation correction may be required beyond the fixture itself.
6. Fault LocationIsolate to a loose fixing, a damaged frangible coupling, or underlying ground/pavement movement.
7. Root CauseConfirm whether the misalignment is an isolated mounting issue or symptomatic of a broader ground/pavement condition affecting multiple fixtures in the area.

Test Points

Root Cause Verification

After realignment, re-measure elevation and azimuth angle against the design aiming diagram to confirm the fixture is within tolerance, and visually confirm consistency with adjacent fixtures at night.

Corrective Action

• Re-align the fixture to the design aiming angle and re-torque mounting/base fixings.
• Replace a damaged or partially sheared frangible coupling.
• Coordinate broader pavement/foundation correction where ground settlement or heave is confirmed as the underlying cause.

Preventive Action

• Include fixture aiming/alignment verification in the periodic PM programme, not only after a reported incident.
• Coordinate with mowing/vehicle operators on fixture locations to reduce impact-related misalignment risk.
• Monitor known settlement-prone areas for recurring alignment drift and address the underlying ground condition proactively.

Related References

SOP: SOP-EDG-26 (Fixture Aiming & Alignment Verification Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46

Diagram: Runway Edge Circuit Single Line Diagram, Fixture Wiring Diagram, Fixture Aiming Diagram

Case Study: Division 25 — Field Case Study Troubleshooting (cross-reference where applicable)