Root Cause Analysis / Failure Investigation

Equipment / System

L-830 series-circuit isolation transformers across CCR-fed loops; maintenance/CMMS failure records, insulation resistance test history, and transformer batch/procurement records.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before removing any transformer for forensic inspection.
• Treat a suspect transformer as potentially still energised by induced voltage from an adjacent live loop until confirmed isolated.
• Bag and tag failed units for lot traceability rather than discarding on site.

Investigation Procedure

1. Data CollectionPull the full failure history for the position/circuit/batch in question spanning at least the last 12–24 months from the CMMS or maintenance log.
2. Trend AnalysisPlot failures by base-can location, transformer batch/lot number, and calendar date to distinguish a location-specific pattern from a batch-specific one.
3. HypothesisDraft 5-Whys or fishbone (Ishikawa) branches for the leading candidate causes — wattage mismatch, batch defect, water ingress, and CCR-side stress — before inspecting the current failed unit.
4. InvestigationPhysically inspect the most recently failed transformer for wattage/tap rating, potting condition, and evidence of moisture versus thermal damage, and cross-check against the design load.
5. InvestigationVerify CCR output voltage and current at that circuit against the design spec, and check for harmonic distortion if the CCR is inverter-based.
6. Root CauseCorrelate the physical evidence with the trend data to select the single leading cause, ruling out the alternatives with specific evidence rather than by elimination alone.

Data Points Reviewed

Root Cause Verification

Install a correctly specified transformer from a known-good batch, correct any identified base-can drainage or CCR-side issue, and monitor insulation resistance and failure recurrence at that specific position for at least two full PM cycles before closing the investigation.

Corrective Action

• Replace the failed transformer with a unit of verified correct wattage/tap rating from a confirmed-good batch.
• Quarantine and return any remaining units from an implicated bad batch, and notify the supplier.
• Remediate the base can (drainage, gasket, can integrity) if water ingress is the confirmed cause.
• Correct CCR output voltage/harmonic issues at the source if the circuit itself is implicated.

Preventive Action

• Add batch/lot number capture to the transformer replacement record in the CMMS to enable early batch-defect detection.
• Set a CMMS trigger for repeat failure at the same position within a defined interval (e.g. two failures in 12 months) to auto-flag for RCA.
• Include transformer wattage/tap verification as a mandatory step on every changeout work order.
• Trend circuit-level insulation resistance rather than relying on single spot readings.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-RCL-12 (Transformer Test and Replacement Procedure)

Standards: FAA AC 150/5345-26 (isolation transformers), IEEE C57.12.91, ISO 9001:2015 Cl. 10.2 (nonconformity and corrective action)

Diagram: Circuit Design Specification and Base-Can Schedule for the affected loop

Case Study: Division 05 — Runway Centreline Light Troubleshooting (RCL-192 single transformer fault); Division 01 — CCR Troubleshooting

Equipment / System

CCR (transformer-type or TSCR/inverter-type), its protection relays/settings, the series circuit and loop it feeds, and the CCR failure/trip log or SCADA/ALCMS event history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the CCR before internal inspection; do not rely on the trip alone as proof of de-energisation.
• Allow discharge time for output capacitors per the manufacturer procedure before touching internal components.
• Coordinate any extended CCR outage with ATC given the runway/taxiway lighting it serves.

Investigation Procedure

1. Data CollectionExport the full trip history for the specific CCR, including trip type, timestamp, and any load/current data logged at the moment of trip.
2. Trend AnalysisPlot trip frequency against time of day, ambient temperature, weather (rain events for earth fault trips), and any recent maintenance activity on the loop.
3. HypothesisSeparate the candidate causes into loop-side (real fault) versus CCR-side (protection or component issue) branches for a fishbone diagram before further testing.
4. InvestigationWith the CCR isolated, megger the full series loop to rule in or out a genuine, still-present insulation fault as the trigger.
5. InvestigationVerify protection relay settings (overcurrent, earth fault threshold, trip delay) against the design calculation for the actual loop impedance and length.
6. Root CauseCross-reference the trip timestamps against the insulation and thermal data to isolate whether the pattern tracks a real loop fault, a settings mismatch, or CCR internal degradation.

Data Points Reviewed

Root Cause Verification

After the identified cause is corrected — loop repair, relay re-setting, or component replacement — monitor the CCR trip log for at least 30 days or one full PM cycle spanning varied load and weather conditions with zero recurrence before closing the RCA.

Corrective Action

• Repair the loop fault if a genuine, still-present insulation or cable fault is confirmed as the trigger.
• Re-calculate and re-set protection relay thresholds to match the actual loop impedance and length.
• Replace degraded CCR internal components identified during inspection.
• Improve CCR house/pit ventilation if thermal trips correlate with ambient conditions.

Preventive Action

• Require a documented fault-location step before any CCR trip reset is logged as resolved, rather than allowing reset-and-move-on.
• Add automatic trip-event logging with timestamp and load snapshot to the CCR/ALCMS configuration if not already present.
• Include protection relay setting verification in the periodic CCR maintenance checklist, not only at commissioning.
• Trend CCR house temperature as a standard PM data point.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-CCR-04 (CCR LOTO Procedure), SOP-CCR-07 (Protection Relay Verification)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5345-10 (CCRs), IEC 61439 (protection coordination)

Diagram: CCR Single-Line Diagram and Protection Coordination Study

Case Study: Division 01 — CCR Troubleshooting; Division 24 — Complete Runway Lighting Failure

Equipment / System

L-824 primary series cable, secondary cable to fixtures, duct banks, pull boxes, and field splices/joints; cable fault location and repair history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the CCR before any cable work; series circuits present a shock hazard beyond the immediate fault point.
• Obtain excavation clearance and utility locates before opening pavement or verge at the repeat-fault location.
• Coordinate airside access and any extended occupancy through ATC/airfield operations.

Investigation Procedure

1. Data CollectionCompile every fault and repair record for the route/joint in question with station chainage or GPS coordinates and dates, going back as far as records allow.
2. Trend AnalysisPlot the fault locations on the as-built route drawing to confirm whether failures cluster at one physical point or recur along a broader section.
3. HypothesisBuild a fishbone diagram separating environmental (water, thermal), mechanical (impact, civil works), and workmanship (splice quality, wrong cable spec) branches for the clustered location.
4. InvestigationExcavate and expose the clustered joint/section, inspect for standing water, splice kit condition, and cable insulation appearance versus a known-good reference sample.
5. InvestigationVerify the installed cable and splice kit specification against the design requirement for that circuit voltage and route.
6. Root CauseMatch the physical evidence at the excavation to the leading fishbone branch, confirming with insulation resistance testing before and after the section is isolated.

Data Points Reviewed

Root Cause Verification

After repair with a correctly specified splice kit and, if required, duct/drainage remediation, megger the full loop end-to-end, re-energise, and re-test at the next two scheduled PM visits with no recurrence before closing the RCA.

Corrective Action

• Re-splice using the correct kit and technique for the circuit voltage class.
• Remediate duct/pull-box drainage or re-route the cable away from a chronically wet section if repair alone will not resolve recurrence.
• Replace cable found to be of incorrect insulation rating for the circuit.
• Improve route marking and depth of cover where mechanical damage is implicated.

Preventive Action

• Log fault location by station/GPS on every repair to make clustering visible over time rather than only after several repeats.
• Standardise splice kit selection and require photo documentation of every buried splice before backfill.
• Flag routes under active civil works for temporary cable protection or re-scheduling of works.
• Include periodic full-loop insulation resistance trending in the PM programme.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-RCL-02 (Series Circuit Fault Location Procedure)

Standards: IEC 60364 (insulation testing), ICAO Annex 14 Vol I, FAA AC 150/5340-30

Diagram: As-Built Duct and Cable Route Drawing

Case Study: Division 05 — Runway Centreline Light Troubleshooting (RCL-193 multiple light failure); Division 24 — Complete Runway Lighting Failure

Equipment / System

L-823 primary connectors, secondary lamp-to-transformer connectors, base cans, and the connector maintenance/replacement history for the affected population.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before disconnecting or handling any connector suspected of internal arcing or moisture contamination.
• Wear appropriate PPE when handling connectors with evidence of corrosion or chemical residue.
• Treat a wet base can as a potential shock hazard even after isolation, until confirmed dry and safe.

Investigation Procedure

1. Data CollectionPull the connector replacement/repair history for the affected population, noting base-can ID, connector type, and grease/torque records where logged.
2. Trend AnalysisDetermine whether failures cluster by base-can design, geographic/drainage zone, connector batch, or maintenance crew/shift.
3. HypothesisDraft fishbone branches for workmanship (grease, torque, seating), design (base-can drainage, connector compatibility), and material (batch defect) causes.
4. InvestigationPerform teardown inspection of several recently failed connectors, checking pin plating, seal condition, and evidence of grease application.
5. InvestigationInspect a sample of the implicated base cans for standing water or drainage defects independent of the connector condition.
6. Root CauseCorrelate teardown findings with the clustering pattern to confirm whether the dominant driver is workmanship, base-can design, or a connector batch defect.

Data Points Reviewed

Root Cause Verification

Reassemble with the specified grease and torque, or replace the base can/connector type where design is implicated, and re-check contact resistance at the next two PM visits with no recurrence before closing the RCA.

Corrective Action

• Re-terminate with correctly specified dielectric grease and connector torque.
• Replace connectors from an implicated defective batch and quarantine remaining stock.
• Remediate base-can drainage where a chronic moisture condition is confirmed.
• Retrain the maintenance crew where a workmanship pattern is confirmed as the driver.

Preventive Action

• Standardise and mandate the approved grease/torque procedure with sign-off on every connector work order.
• Add connector batch/date-code capture to the CMMS for early batch-defect detection.
• Include base-can drainage checks as a standard PM item independent of connector condition.
• Provide refresher training on connector assembly technique at defined intervals.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-RCL-03 (Fixture Replacement Procedure)

Standards: FAA AC 150/5345-26, FAA AC 150/5345-46 (L-852), ICAO Annex 14 Vol I

Diagram: Base-Can Detail Drawing and Connector Assembly Specification

Case Study: Division 05 — Runway Centreline Light Troubleshooting (RCL-192 fixture-level fault)

Equipment / System

Complete inset or elevated AGL fixture assemblies (housing, optics, lamp/LED module, base), and the fixture-level failure history across the affected population.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before fixture removal.
• Coordinate airside access and any extended occupancy through ATC/airfield operations.
• Use FOD-safe tools and account for every item before leaving the movement area.

Investigation Procedure

1. Data CollectionCompile the full failure history for the fixture position/model/batch across at least 12–24 months, noting failure mode for each event.
2. Trend AnalysisMap failure locations against known high-stress zones (jet blast, snow-plough routes, vehicle crossings) and against fixture batch/serial data.
3. HypothesisSeparate location-driven (environmental/mechanical) from fixture-driven (design/batch) candidate causes on a fishbone diagram.
4. InvestigationPhysically inspect the current failed fixture and, where available, a retained failed unit from the same position for a consistent damage signature.
5. InvestigationCompare the fixture model/duty-cycle rating installed at that location against the design requirement for that zone.
6. Root CauseConfirm whether the dominant driver is the location (supporting fixture-type upgrade or physical protection) or the fixture itself (supporting a batch/model-level corrective action).

Data Points Reviewed

Root Cause Verification

Install the corrected fixture type or remediate the location-specific stressor, then monitor that position specifically for at least two PM cycles or one full winter/summer season, whichever is more relevant to the confirmed cause, before closing the RCA.

Corrective Action

• Upgrade to a fixture model rated for the actual duty cycle/exposure at that location if a mismatch is confirmed.
• Add physical protection (frangible mounting, reinforced housing) where jet-blast or vehicle impact is confirmed as the driver.
• Replace remaining units from a confirmed defective batch and notify the supplier.
• Correct any confirmed power-quality issue on the feeding circuit.

Preventive Action

• Flag high-stress zones in the CMMS so repeat failures there are recognised as a pattern rather than treated as isolated events.
• Capture fixture batch/serial on every installation and replacement for future traceability.
• Review fixture specification against zone duty-cycle requirements at design/procurement stage for future projects.
• Reinforce PM inspection thoroughness at flagged high-stress locations.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-RCL-03 (Fixture Replacement Procedure)

Standards: FAA AC 150/5345-46 (L-852), ICAO Annex 14 Vol I, ISO 9001:2015 Cl. 8.7

Diagram: Runway/Taxiway High-Stress Zone Map

Case Study: Division 05 — Runway Centreline Light Troubleshooting; Division 25 — Field Case Study Troubleshooting

Equipment / System

LED light-emitting modules and their drivers within AGL fixtures, plus LED failure and photometric test history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before removing any LED module or driver.
• Allow LED driver capacitors to discharge per manufacturer procedure before handling.
• Use appropriate PPE when handling modules with suspected moisture or chemical contamination.

Investigation Procedure

1. Data CollectionCompile the LED/driver failure history for the position/batch/model, including hours in service where duty logging is available.
2. Trend AnalysisCompare actual hours-to-failure against the manufacturer's rated LED life to quantify the severity of the shortfall, and check for batch or location clustering.
3. HypothesisDraft fishbone branches for driver mismatch, thermal design, batch defect, and power-quality causes.
4. InvestigationMeasure driver output current/voltage against the LED module's rated range under actual field conditions.
5. InvestigationUse thermal imaging on an operating fixture at that position to check for elevated junction/heat-sink temperature versus a known-good reference fixture.
6. Root CauseCorrelate the electrical and thermal measurements with the failure-mode evidence from teardown to isolate driver mismatch, thermal design, or batch defect as the leading cause.

Data Points Reviewed

Root Cause Verification

Install a correctly matched driver/LED combination or corrected thermal design, then re-test photometric output immediately and again at the next scheduled photometric survey, with hours-in-service tracked at that position to confirm life has returned to expected range.

Corrective Action

• Replace the driver with one correctly matched to the LED module's rated current/voltage range.
• Improve thermal management at the fixture design/location if elevated temperature is confirmed.
• Replace remaining modules from a confirmed defective batch and notify the supplier.
• Correct any confirmed power-quality issue at the CCR/driver interface.

Preventive Action

• Capture LED/driver batch and installation date in the CMMS to enable hours-to-failure trending against rated life.
• Include a driver-to-module compatibility check as a standard step whenever either component is replaced independently.
• Add thermal imaging of a sample of fixtures to the periodic PM programme in warmer climates or high-ambient locations.
• Trend photometric survey results by fixture batch, not only by division.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-PHM-01 (Photometric Survey Procedure)

Standards: FAA AC 150/5345-46 (L-852 LED), ICAO Annex 14 Vol I Appendix 2 (chromaticity/intensity), IESNA LM-80/TM-21 (LED lumen maintenance)

Diagram: LED Fixture Thermal and Electrical Design Specification

Case Study: Division 05 — Runway Centreline Light Troubleshooting; Division 26 — Photometric Compliance Troubleshooting

Equipment / System

L-858 illuminated signs (mandatory instruction and information signs), their internal light sources/drivers, panel assemblies, and sign failure/repair history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before opening the sign housing.
• Confirm the sign structure is stable and properly anchored before working at height or in proximity to moving traffic.
• Coordinate airside access through ATC/airfield operations.

Investigation Procedure

1. Data CollectionCompile the failure/repair history for the specific sign ID or sign class over the available record period.
2. Trend AnalysisDetermine whether failures cluster at one physical sign, a sign design/batch, or a circuit-wide pattern affecting all signs on that CCR.
3. HypothesisDraft fishbone branches for thermal, moisture ingress, component mismatch, and location/vibration causes.
4. InvestigationOpen the sign housing and inspect for heat discolouration, moisture staining, seal condition, and cooling fan operation.
5. InvestigationVerify the fitted ballast/driver specification against the light source actually installed.
6. Root CauseCorrelate the internal inspection findings with the failure-history pattern to confirm the leading cause before closing on a corrective action.

Data Points Reviewed

Root Cause Verification

After repair or component correction, re-inspect the sign at the next two scheduled PM visits and confirm no recurrence of the same failure mode, with an interim inspection at approximately 90 days if the sign is in a high-risk category.

Corrective Action

• Replace the failed internal component with one of correct specification for the fitted light source.
• Restore door seal/gland integrity where moisture ingress is confirmed.
• Improve ventilation or cooling-fan reliability where thermal build-up is confirmed.
• Replace panel/harness from a confirmed defective batch.

Preventive Action

• Add sign ID-level failure tracking to the CMMS to make repeat-failure patterns visible earlier.
• Include door seal and cooling-fan checks as standard PM items for illuminated signs.
• Verify ballast/driver-to-light-source compatibility whenever either component is serviced.
• Review sign siting relative to known vibration/traffic-proximity zones for future placements.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-SGN-01 (Illuminated Sign Maintenance Procedure)

Standards: FAA AC 150/5345-44 (L-858 signs), ICAO Annex 14 Vol I

Diagram: Sign Internal Wiring and Ventilation Detail Drawing

Case Study: Division 09 — Illuminated Sign Troubleshooting; Division 25 — Field Case Study Troubleshooting

Equipment / System

AGL earthing/grounding system — CCR earth bar, transformer secondary earthing, fixture body earthing, and earth-loop/earth-fault protection settings, plus the earth-fault trip and earth resistance test history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before testing or working on earthing connections.
• Treat any exposed conductive part as potentially live until earth continuity and isolation are confirmed.
• Use appropriate PPE when excavating to expose buried earth electrodes or ring conductors.

Investigation Procedure

1. Data CollectionCompile the earth-fault trip and earth-loop resistance test history for the circuit/location over the available record period.
2. Trend AnalysisCheck whether the pattern correlates with season/rainfall (soil resistivity) or is stable regardless of weather, pointing instead to a persistent physical defect.
3. HypothesisDraft fishbone branches for corrosion/bonding, soil resistivity, a genuine insulation fault, and protection-setting causes.
4. InvestigationInspect and test each earth bonding point along the suspect section for continuity, torque, and corrosion, working outward from the last reported location.
5. InvestigationMegger the circuit to rule in or out a genuine insulation-to-earth fault distinct from the earthing system itself.
6. Root CauseCorrelate the bonding/continuity findings and the seasonal trend with the trip pattern to isolate whether the earthing system, the insulation, or the protection setting is the true driver.

Data Points Reviewed

Root Cause Verification

After remediation, re-test earth-loop resistance immediately and again after the next significant rainfall event or seasonal change, confirming the reading remains within the acceptable threshold before closing the RCA.

Corrective Action

• Re-terminate corroded or loose bonding points with correctly rated, compatible-metal hardware and corrosion protection.
• Add supplementary earth electrodes or improve the ring conductor where soil resistivity is confirmed as a contributing factor.
• Repair the genuine insulation fault if confirmed, separate from any earthing system work.
• Re-calculate and adjust the earth-fault protection threshold if it is confirmed tighter than the circuit's design tolerance.

Preventive Action

• Include earth-loop resistance testing and trending as a standard PM item, not only a response to a trip.
• Standardise bonding hardware and corrosion-protection method for dissimilar-metal joints.
• Flag locations with historically marginal earth resistance for closer seasonal monitoring.
• Review earth-fault protection settings against actual circuit leakage characteristics at commissioning and after any circuit modification.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-EARTH-01 (Earthing System Test and Bonding Procedure)

Standards: IEC 60364-5-54 (earthing arrangements), IEEE 142 (grounding practice), ICAO Annex 14 Vol I

Diagram: As-Built Earthing and Grounding Ring Drawing

Case Study: Division 01 — CCR Troubleshooting; Division 22 — Lightning and Surge Protection Troubleshooting

Equipment / System

Base cans, pull boxes, duct entries, sign housings, and CCR house/pit drainage systems across the affected location(s), plus the moisture-related inspection and repair history.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before opening any can, box, or pit suspected of water ingress.
• Treat standing water in an electrical enclosure as an electrocution hazard until isolation and de-energisation are confirmed.
• Use appropriate PPE and confined-space precautions where applicable for pit entry.

Investigation Procedure

1. Data CollectionCompile the moisture inspection and repair history for the specific location, including what remediation was attempted at each visit.
2. Trend AnalysisCheck whether the recurrence correlates with rainfall events, season, or is present even in dry periods, pointing to a persistent groundwater or drainage issue rather than surface infiltration.
3. HypothesisDraft fishbone branches for site drainage/grading, absent drainage path, seal/gasket quality, and duct-entry sealing.
4. InvestigationWith the enclosure isolated and pumped out, inspect the seal, duct entries, and any drainage provision (weep hole, sump) for function versus design intent.
5. InvestigationReview or survey the local site grading and drainage relative to the can/pit to identify whether surface water is being directed toward it.
6. Root CauseCorrelate the seasonal/rainfall pattern with the physical inspection findings to distinguish a groundwater/grading issue from a seal-only issue.

Data Points Reviewed

Root Cause Verification

After remediation — corrected drainage, re-sealed duct entries, or improved site grading — inspect the location after the next significant rainfall event and again at the following PM visit to confirm no recurrence before closing the RCA.

Corrective Action

• Install or restore a functional drainage path (weep hole, gravel sump, drain line) at the affected can/pit.
• Re-seal duct entries with correctly rated sealant/boot to stop water tracking along the cable route.
• Regrade the local surface to direct water away from the enclosure where site drainage is implicated.
• Replace with correctly specified gasket/seal material and confirm proper seating.

Preventive Action

• Include drainage function checks, not just visual seal inspection, in the periodic PM programme for cans, boxes, and pits.
• Flag chronically wet locations in the CMMS for closer seasonal monitoring and priority in drainage improvement projects.
• Standardise sealant/gasket specification for duct entries and enclosure lids.
• Review site grading as part of any nearby civil works or resurfacing project.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-CIVIL-02 (Drainage and Base-Can Remediation Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, local civil/drainage design codes

Diagram: Site Drainage and Grading Survey; Base-Can Detail Drawing

Case Study: Division 05 — Runway Centreline Light Troubleshooting (RCL-199 base-can water ingress)

Equipment / System

Primary and secondary cable insulation, transformer winding insulation, and the insulation resistance test/trend history across the affected population.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before insulation testing or component work.
• Ensure the correct test voltage is used for the rated insulation class to avoid inducing damage during testing itself.
• Use appropriate PPE when working in areas of known chemical exposure.

Investigation Procedure

1. Data CollectionCompile the full insulation resistance trend for the affected location/component, including test voltage, technician, and date for each reading.
2. Trend AnalysisPlot the trend to distinguish a genuine progressive decline from test-to-test variability, and check whether the decline resumed immediately after the last repair or only after a delay.
3. HypothesisDraft fishbone branches for moisture, age/end-of-life, mechanical stress, electrical overstress, and chemical exposure.
4. InvestigationPhysically inspect the insulation at the failing location for visible degradation signature (cracking, discolouration, tracking) consistent with one of the candidate causes.
5. InvestigationCross-check installation date against design life and compare with insulation trends at comparable-age locations elsewhere on the field.
6. Root CauseCorrelate the visible degradation signature and trend shape with the leading candidate cause, distinguishing genuine physical decline from a measurement-consistency artefact.

Data Points Reviewed

Root Cause Verification

After remediation (moisture elimination, component replacement, or mechanical stress correction), re-test insulation resistance immediately and trend it at every subsequent PM visit for at least one year to confirm the decline has stopped before closing the RCA.

Corrective Action

• Eliminate the confirmed moisture source rather than repairing only the visible symptom.
• Replace insulation/cable or transformer confirmed to have reached genuine end of design life.
• Correct the mechanical stress condition (support, routing, or vibration isolation) at the affected point.
• Address confirmed CCR overvoltage/harmonic issues at the source.

Preventive Action

• Standardise test voltage and procedure across all technicians to remove measurement inconsistency as a confounding factor.
• Trend insulation resistance by installation-date cohort to anticipate end-of-life replacement needs proactively.
• Include chemical exposure risk in site risk assessments for de-icing and fuelling areas.
• Review CCR output quality periodically against insulation withstand ratings for older cable generations.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-TEST-03 (Insulation Resistance Test Procedure)

Standards: IEC 60364, IEEE 43 (recommended practice for insulation testing), ICAO Annex 14 Vol I

Diagram: Circuit Insulation Trend Chart by Installation Cohort

Case Study: Division 05 — Runway Centreline Light Troubleshooting; Division 21 — Preventive Maintenance Troubleshooting

Equipment / System

AGL fixture optics, lamp/LED modules, and the photometric survey history (intensity, chromaticity, beam pattern) across the affected population.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before optic cleaning, lamp replacement, or alignment work.
• Coordinate airside access and survey timing through ATC/airfield operations.
• Use appropriate PPE when handling contaminated optics (de-icing fluid, fuel residue).

Investigation Procedure

1. Data CollectionCompile the photometric survey trend for the affected fixture group across all available survey cycles, noting intensity, chromaticity, and beam-spread results.
2. Trend AnalysisDetermine whether the decline resumes at the same rate after each cleaning/re-lamp cycle, pointing to a re-accumulation or lumen-depreciation cause rather than a one-off fault.
3. HypothesisDraft fishbone branches for contamination re-accumulation, lumen depreciation/end of life, optic degradation, alignment drift, and equipment calibration.
4. InvestigationPhysically inspect the optics under magnification/UV light for damage not visible to the naked eye, and check mounting hardware for looseness.
5. InvestigationCross-check the photometric test equipment's calibration date and, where practical, cross-validate with a second calibrated instrument.
6. Root CauseCorrelate the survey trend shape, physical inspection, and equipment calibration status to isolate whether re-accumulation, end-of-life, or a measurement artefact is the true driver.

Data Points Reviewed

Root Cause Verification

After the corrected cause is addressed — revised cleaning interval, fixture/lamp replacement, optic replacement, or mounting correction — re-survey at the next scheduled cycle and confirm the decline rate has normalised before closing the RCA.

Corrective Action

• Shorten the cleaning interval for fixtures in the confirmed high-contamination zone.
• Replace lamp/LED modules confirmed to be at or beyond rated lumen-maintenance life.
• Replace optics showing confirmed UV or mechanical degradation.
• Re-torque and, where recurring, upgrade the mounting hardware for fixtures with confirmed alignment drift.

Preventive Action

• Segment the PM cleaning schedule by contamination-risk zone rather than applying a single field-wide interval.
• Trend photometric results by fixture installation cohort to anticipate end-of-life replacement proactively.
• Include mounting hardware torque-check as a standard step whenever a fixture is re-aligned.
• Maintain photometric test equipment calibration on a documented schedule and cross-validate periodically.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-PHM-01 (Photometric Survey Procedure)

Standards: ICAO Annex 14 Vol I Appendix 2, FAA AC 150/5340-30, IESNA measurement practice

Diagram: Photometric Survey Trend Chart by Fixture Cohort

Case Study: Division 26 — Photometric Compliance Troubleshooting; Division 21 — Preventive Maintenance Troubleshooting

Equipment / System

Elevated and inset AGL fixtures with adjustable aim, PAPI/APAPI units, and the alignment survey/adjustment history for the affected unit(s).

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before working on or near an energised elevated fixture.
• Use fall-protection and stable access equipment when working on elevated units.
• Coordinate airside access through ATC/airfield operations, particularly for PAPI/approach lighting units.

Investigation Procedure

1. Data CollectionCompile the alignment survey and adjustment history for the specific unit, including the magnitude and direction of drift at each cycle.
2. Trend AnalysisDetermine whether the drift is consistently in the same direction (pointing to settlement or a directional vibration source) or random (pointing to a loose mechanism or measurement inconsistency).
3. HypothesisDraft fishbone branches for foundation settlement, aiming mechanism wear, vibration source, procedure inconsistency, and survey measurement error.
4. InvestigationInspect the foundation for visible settlement, cracking, or tilt, and check the aiming mechanism hardware for wear or inability to hold torque.
5. InvestigationCross-check the survey reference points and equipment used at that location for consistency with the standard procedure.
6. Root CauseCorrelate the drift direction/pattern with the physical foundation and hardware inspection findings to isolate the true driver from a measurement artefact.

Data Points Reviewed

Root Cause Verification

After remediation — foundation repair, mounting hardware replacement, or procedure correction — re-survey at the next scheduled cycle and confirm the drift has stopped or fallen within normal tolerance before closing the RCA.

Corrective Action

• Repair or reinforce the foundation where settlement is confirmed.
• Replace worn aiming mechanism hardware with a unit that reliably holds torque.
• Relocate or add vibration isolation if a specific external vibration source is confirmed.
• Standardise and retrain on the aiming procedure if inconsistency is confirmed as a contributing factor.

Preventive Action

• Flag units with a history of repeat drift for closer-interval survey until the pattern is resolved.
• Include foundation visual inspection as a standard item during every alignment survey.
• Standardise aiming mechanism hardware specification across the fleet to reduce hold-torque variability.
• Periodically cross-validate survey equipment and reference points.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-PAPI-01 (PAPI/APAPI Alignment Procedure)

Standards: ICAO Annex 14 Vol I (PAPI/APAPI alignment tolerance), FAA AC 150/5345-28

Diagram: PAPI/Fixture Foundation and Aiming Mechanism Detail Drawing

Case Study: Division 10 — PAPI/APAPI Troubleshooting; Division 26 — Photometric Compliance Troubleshooting

Equipment / System

The complete circuit — CCR, series/parallel loop, all fixtures and transformers on it — and the circuit-level fault and repair history distinct from individual component records.

Possible Causes

Required Tools

Safety Precautions

• LOTO the CCR before any full-loop testing or circuit-wide work.
• Coordinate any extended circuit outage with ATC given its runway/taxiway function.
• Treat the full loop as energised until confirmed isolated at the CCR.

Investigation Procedure

1. Data CollectionCompile the circuit-level fault history (not just individual component swaps) for the specific circuit over the available record period.
2. Trend AnalysisCheck whether the circuit's current/output has trended downward over time even between discrete fault events, suggesting a cumulative margin issue rather than isolated faults.
3. HypothesisDraft fishbone branches for cumulative component degradation, original design undersizing, CCR calibration, and unauthorised topology change.
4. InvestigationCompare the current as-built fixture count and loop length against the original design calculation to check for unreconciled additions.
5. InvestigationPerform a full-loop insulation resistance test and CCR output verification, rather than testing only the most recently faulted component.
6. Root CauseCorrelate the design-margin calculation, CCR calibration status, and full-loop test results to determine whether the circuit is operating within its intended margin or has been pushed beyond it.

Data Points Reviewed

Root Cause Verification

After the design margin is restored (CCR recalibration, circuit re-design/derating, or component upgrade), monitor circuit-level fault frequency for at least two full PM cycles and confirm it has returned to a rate consistent with the wider field before closing the RCA.

Corrective Action

• Recalibrate or replace CCR components confirmed to be degraded.
• Re-validate and, if necessary, re-design the circuit for its current actual fixture count and loop length.
• Replace marginal components identified during full-loop testing, not only the most recently failed one.
• Formalise the topology change record and re-issue the circuit design calculation.

Preventive Action

• Require full-loop verification, not just point-fix testing, whenever a circuit records more than one fault within a defined period.
• Establish a change-control process requiring circuit re-calculation whenever fixtures are added or the loop is extended.
• Include CCR output calibration checks in the periodic PM programme.
• Track circuit-level (not only fixture-level) fault frequency in the CMMS to catch this pattern earlier.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-CCR-04 (CCR LOTO Procedure), SOP-DESIGN-02 (Circuit Design Change Control)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-10 (CCR)

Diagram: Circuit Design Calculation and As-Built Topology Drawing

Case Study: Division 01 — CCR Troubleshooting; Division 24 — Complete Runway Lighting Failure

Equipment / System

ALCMS/SCADA communication network — fibre, copper, or wireless links between the control room and field CCR/monitoring nodes — and the communication fault/downtime log.

Possible Causes

Required Tools

Safety Precautions

• Follow LOTO/isolation procedures appropriate to the specific equipment being tested, particularly where communication hardware shares a cabinet with live power equipment.
• Use fibre-optic safety precautions (no direct eye exposure) when testing with an OTDR or visual fault locator.

Investigation Procedure

1. Data CollectionCompile the communication downtime log for the specific node/link, including duration and time of day/environmental conditions at each event.
2. Trend AnalysisCheck whether the outages correlate with temperature extremes, specific equipment operating nearby (EMI), or firmware update events.
3. HypothesisDraft fishbone branches for physical layer defect, EMI, configuration drift, power supply instability, and firmware/software fault.
4. InvestigationTest the physical link (OTDR for fibre, cable tester for copper) end-to-end rather than only at the point of the most recent apparent repair.
5. InvestigationCheck the remote node's power supply/UPS condition and firmware version against the current approved baseline.
6. Root CauseCorrelate the outage pattern with the physical layer test results and power/firmware findings to isolate the true driver of the recurring dropout.

Data Points Reviewed

Root Cause Verification

After the physical, power, or configuration issue is corrected, monitor the communication uptime log for the specific node for at least 30 days including a range of temperature/weather conditions with no recurrence before closing the RCA.

Corrective Action

• Re-splice or replace the physical link segment confirmed to have a recurring defect.
• Relocate or shield the link from a confirmed EMI source.
• Replace the degraded UPS/battery at the remote node.
• Standardise and re-apply the correct firmware/configuration baseline across affected devices.

Preventive Action

• Include physical-layer link testing (not just ping/uptime checks) in the periodic network maintenance programme.
• Establish a configuration management baseline with change-control for firmware and network settings.
• Add UPS/battery health monitoring to the remote node PM checklist.
• Track communication downtime by node in the CMMS to catch repeat-node patterns earlier.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-COMMS-01 (ALCMS/SCADA Network Maintenance Procedure)

Standards: ICAO Annex 14 Vol I (monitoring requirements), relevant network/telecom standards (e.g. TIA/EIA-568 for cabling)

Diagram: ALCMS/SCADA Network Topology Diagram

Case Study: Division 20 — ALCMS/SCADA Troubleshooting

Equipment / System

The maintenance process itself — work order records, PM checklists, technician assignment history, and spares/parts records — cross-referenced against the equipment fault history it is meant to resolve.

Possible Causes

Required Tools

Safety Precautions

• Apply standard LOTO and access procedures for any physical re-inspection performed as part of the RCA.
• Ensure any process change identified does not compromise established safety steps in pursuit of speed.

Investigation Procedure

1. Data CollectionIdentify the set of work orders where the same fault recurred within a defined short interval (e.g., 90 days) of closure, and pull the full work order detail for each.
2. Trend AnalysisCheck whether the repeat pattern clusters around a specific technician, crew, shift, part number, or checklist/SOP version.
3. HypothesisDraft fishbone branches for checklist/SOP adequacy, technician competency, parts availability/specification, closure verification practice, and time/access pressure.
4. InvestigationCompare the closure notes and parts used against the SOP requirement for that fault type to check for deviation.
5. InvestigationInterview the technician(s) involved (non-punitively, focused on process) to understand constraints faced at the time of the original repair.
6. Root CauseCorrelate the work-order pattern, SOP compliance check, and technician input to identify whether the process, training, parts, or verification step is the leading driver.

Data Points Reviewed

Root Cause Verification

After the process gap is corrected (checklist update, training, parts stocking, or closure-verification requirement), monitor the specific fault type's recurrence rate for at least two PM cycles and confirm it has dropped to the expected baseline before closing the RCA.

Corrective Action

• Update the PM checklist/SOP to include the missing root-cause verification step for that fault type.
• Provide targeted retraining where a technician/crew-specific pattern is confirmed.
• Correct spares stocking to ensure the correct part specification is available when needed.
• Add a mandatory post-repair verification step before work-order closure for that fault category.

Preventive Action

• Introduce a repeat-fault flag in the CMMS that auto-escalates any fault recurring within a defined interval of a prior closure.
• Periodically audit closed work orders against SOP compliance, not only open/overdue ones.
• Review technician competency on high-repeat-rate fault types as part of ongoing training planning.
• Foster a non-punitive reporting culture so time/access pressures are surfaced rather than hidden in closure notes.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-QA-01 (Work Order Closure and Verification Procedure)

Standards: ISO 9001:2015 Cl. 10.2 (corrective action), ISO 55001 (asset management)

Diagram: Work Order Process Flow Diagram

Case Study: Division 21 — Preventive Maintenance Troubleshooting

Equipment / System

Not equipment-specific — applies across CCR, cable, fixture, and sign work; relevant records are the specific work order, procedure/SOP in force at the time, and training records for the individual(s) involved.

Possible Causes

Required Tools

Safety Precautions

• Conduct the investigation and interviews in a non-punitive, just-culture manner to encourage honest input rather than defensive answers.
• Do not use the RCA process to assign blame; focus on identifying and correcting systemic contributing factors.
• Where an immediate safety risk is identified during investigation, address it without waiting for the full RCA to conclude.

Investigation Procedure

1. Data CollectionGather the factual timeline of the event — what was done, by whom, using which procedure and parts, and under what conditions (time, access window, fatigue).
2. InterviewConduct a structured, non-punitive interview with the individual(s) involved, focused on understanding the conditions and decision points rather than assigning fault.
3. 5-WhysAsk "why" repeatedly against the immediate action to trace back from the error itself to the systemic condition that made it possible or likely.
4. ClassificationClassify the contributing factors using a human-factors framework (e.g., procedure adequacy, training adequacy, environmental/workload conditions, design/error-proofing) rather than stopping at "operator error."
5. DistinctionExplicitly distinguish an unintentional slip/lapse/mistake from a deliberate procedural violation, since the two require different corrective paths.
6. Root CauseConfirm the systemic root cause (procedure, training, workload, or design) that, if corrected, would prevent a similarly-conditioned individual from making the same error.

Data Points Reviewed

Root Cause Verification

After the systemic contributing factor is corrected (procedure revision, training, workload adjustment, or design/error-proofing change), monitor for recurrence of the same error type across the team, not just the individual, over the following review period before closing the RCA.

Corrective Action

• Revise the SOP/procedure if it was unclear, outdated, or mismatched to actual field conditions.
• Provide targeted training to close the specific competency gap identified.
• Adjust scheduling/workload where fatigue or unreasonable time pressure was a contributing factor.
• Address the specific event outcome (equipment repair, safety correction) independently of the systemic corrective action.

Preventive Action

• Introduce error-proofing (poka-yoke) design changes where a look-alike or ambiguous component/connector contributed to the error.
• Build the lesson into onboarding and refresher training for the wider team, not only the individual involved.
• Review scheduling practices to avoid systemic fatigue or excessive time pressure on safety-relevant tasks.
• Maintain a just-culture reporting environment so similar near-misses are reported early rather than hidden.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-HR-01 (Just Culture and Non-Punitive Investigation Procedure)

Standards: ISO 9001:2015 Cl. 10.2, ICAO Doc 9859 (Safety Management Manual — human factors principles)

Diagram: HFACS or Equivalent Human-Factors Classification Chart

Case Study: Division 25 — Field Case Study Troubleshooting

Equipment / System

Applies across newly installed or recently reworked fixtures, cable, transformers, CCRs, and signs; relevant records are the installation work package, inspection/test records (ITP), and as-built documentation from the original installation.

Possible Causes

Required Tools

Safety Precautions

• LOTO the circuit before any re-inspection or rework of the suspect installation.
• Treat any newly discovered installation defect as potentially affecting adjacent or similar installations from the same work package, pending wider inspection.

Investigation Procedure

1. Data CollectionPull the original installation work package, ITP records, and as-built drawing revision used for the specific item, and confirm which drawing revision was current at the time.
2. 5-WhysTrace from the physical defect found back through the installation steps to identify at which stage the deviation from specification occurred.
3. ClassificationDetermine whether the root cause is a documentation gap (wrong/ambiguous drawing), a process gap (ITP did not catch it), a training gap, or an unauthorised site change.
4. InvestigationInspect a sample of similar installations from the same work package or installation crew/date to determine whether the error is isolated or systemic.
5. Cross-CheckCompare the ITP sign-off record against what was physically found to identify whether the inspection step was skipped, performed incorrectly, or the criteria itself was inadequate.
6. Root CauseConfirm whether the root cause sits with the design documentation, the ITP/inspection process, installer competency, or an unauthorised site substitution.

Data Points Reviewed

Root Cause Verification

After rework to the correct specification and, where a systemic pattern is found, re-inspection of the full affected batch, confirm compliance across the sample and monitor for recurrence of the same defect type on any subsequent installation work before closing the RCA.

Corrective Action

• Rework the specific item to the correct current specification.
• Extend inspection to the full batch/work package if a systemic pattern is confirmed, and rework any further non-conforming items found.
• Correct the design documentation if it was found to be ambiguous or outdated at the time of installation.
• Formalise any site substitution that was made without proper change-control approval, or reverse it if not acceptable.

Preventive Action

• Strengthen the ITP to explicitly cover the specific defect type found, with hold/witness points where appropriate.
• Implement document control to ensure only the current drawing revision is available to installation crews.
• Provide targeted training on the specific technique found deficient.
• Require formal change-control sign-off for any on-site material or method substitution.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-QA-02 (Inspection and Test Plan Procedure), SOP-DESIGN-02 (Design Change Control)

Standards: ISO 9001:2015 Cl. 8.5/8.7, ICAO Annex 14 Vol I, applicable FAA AC/IS installation standards for the component type

Diagram: Original Installation Work Package and As-Built Drawing

Case Study: Division 25 — Field Case Study Troubleshooting

Equipment / System

Applies at the system/design level — circuit design calculations, component specification selection, and design drawings — rather than to any single physical unit; relevant records are the original design calculation package and any design change history.

Possible Causes

Required Tools

Safety Precautions

• Where a design error has immediate safety implications (e.g., undersized protection, structural inadequacy), flag for urgent interim mitigation without waiting for the full RCA to conclude.
• LOTO affected circuits before any physical verification testing.

Investigation Procedure

1. Data CollectionPull the original design calculation package, design basis, and the standard/version in force at the time of design.
2. Independent Re-CalculationIndependently re-calculate the parameter in question using current methodology and compare against the original design figure.
3. Trend AnalysisCheck whether the defect appears consistently across all units designed to the same specification, confirming a design-level (not installation-level) cause.
4. ClassificationDetermine whether the root cause is an assumption/methodology error, a superseded standard not yet reviewed, a missing design-check step, or an invalidating field change made without design review.
5. Cross-CheckReview the design review/checking sign-off record to determine whether an independent check was performed and what it covered.
6. Root CauseConfirm the specific design element and cause, and quantify the population of installed units affected by the same design.

Data Points Reviewed

Root Cause Verification

After the design is corrected and the affected population is identified and remediated (or a phased remediation plan is in place), verify a sample of remediated units against the corrected design and confirm the defect does not recur on any new installation using the corrected design before closing the RCA.

Corrective Action

• Issue a corrected design calculation/specification and re-issue affected drawings.
• Remediate installed units within the affected population according to a risk-prioritised plan.
• Update the design standard reference if a superseded version was in use.
• Add or strengthen the independent design-check step if that was found to be the gap.

Preventive Action

• Require formal design review against any field changes (added load, circuit extension) that could invalidate the original design basis.
• Establish a periodic review cycle to check installed designs against current standard revisions.
• Validate design calculation tools/software against known reference cases periodically.
• Maintain a register of standard design specifications and their applicable population for efficient future updates.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-DESIGN-01 (Design Calculation and Review Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, applicable IS/IEC design standards for the component

Diagram: Original Design Calculation Package and Corrected Design Drawing

Case Study: Division 24 — Complete Runway Lighting Failure

Equipment / System

Applies to the specific material/component in question (cable insulation compound, transformer potting, connector polymer, fixture housing alloy, LED encapsulant) and the batch/supplier record for that material.

Possible Causes

Required Tools

Safety Precautions

• Handle failed material samples appropriately, particularly where thermal or chemical decomposition products may be present.
• LOTO the circuit before removing any sample for analysis.
• Package and label retained samples for chain-of-custody if supplier/warranty claims may follow.

Investigation Procedure

1. Data CollectionRetain a properly documented sample of the failed material/component and record its batch/lot number, installation date, and service conditions.
2. Laboratory AnalysisArrange metallurgical, polymer, or chemical analysis of the failed sample as appropriate, comparing against the original material specification and a known-good reference sample.
3. Trend AnalysisCheck failure incidence against batch/lot number and installation date to determine whether the defect is confined to an identifiable population.
4. Statistical AnalysisWhere enough data exists, perform a Weibull or similar life-distribution analysis to determine whether failures are occurring earlier than the expected distribution for genuine end-of-life wear-out.
5. Supplier VerificationCross-check the material specification and qualification certificate against what was actually supplied and installed, including any unauthorised substitution.
6. Root CauseConfirm whether the material defect is a supplier/batch issue, a specification-adequacy issue, a storage/handling issue, or in fact normal expected end-of-life behaviour.

Data Points Reviewed

Root Cause Verification

After replacement with verified-conforming material and, where a batch defect is confirmed, removal or monitoring of the remaining affected population, track failure incidence in that population over the following review period and confirm it returns to the expected baseline rate before closing the RCA.

Corrective Action

• Replace the failed component with material verified against a current, conforming certificate.
• Quarantine and, where warranted, proactively replace remaining stock or installed units from a confirmed defective batch.
• Pursue a supplier corrective action / warranty claim where the batch defect originates with the manufacturer.
• Correct the material specification if it was found to be inadequate for the actual duty, independent of the batch issue.

Preventive Action

• Require batch/lot traceability capture at installation for materials with known criticality, to enable faster batch-level RCA in future.
• Add incoming material inspection/certificate verification as a standard receiving step for critical components.
• Periodically request supplier quality data and any known field-issue notifications for qualified materials.
• Review material specifications against actual field duty conditions periodically, not only at initial qualification.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-QA-03 (Incoming Material Inspection Procedure)

Standards: ISO 9001:2015 Cl. 8.4/8.7, relevant material standards (e.g. IEC/IS cable and polymer standards) for the component

Diagram: Material Specification and Batch Traceability Record

Case Study: Division 05 — Runway Centreline Light Troubleshooting

Equipment / System

Applies to the specific manufactured component (transformer, CCR module, connector, fixture, LED driver) and its manufacturing/quality record — production batch, factory acceptance test (FAT) data, and quality escape history.

Possible Causes

Required Tools

Safety Precautions

• Handle and store the failed unit for teardown analysis with appropriate LOTO and PPE for any residual stored energy (capacitors, potted assemblies).
• Package and label the unit for chain-of-custody if a manufacturer warranty/quality claim will follow.

Investigation Procedure

1. Data CollectionRecord the manufacturer, model, batch/production date, and serial number of the failed unit, and pull FAT records if available.
2. Teardown AnalysisPerform a controlled teardown of the failed unit to identify the specific defect signature — assembly, soldering, potting, or component placement issue.
3. Trend AnalysisCheck failure incidence against production batch/date range to determine whether the defect is confined to an identifiable manufacturing run.
4. BenchmarkWhere possible, obtain and inspect a unit from a different, unaffected batch of the same model to confirm the defect is batch-specific rather than inherent to the design.
5. Manufacturer LiaisonShare the teardown findings with the manufacturer and request their internal quality/process records for the implicated batch.
6. Root CauseConfirm whether the defect originates from a process control failure, a FAT coverage gap, a design-for-manufacture weakness, or an isolated single-unit assembly error.

Data Points Reviewed

Root Cause Verification

After replacement with a unit confirmed from an unaffected batch or corrected production, and any manufacturer corrective action (process fix, expanded FAT coverage) is confirmed in place, track failure incidence in the remaining installed population for the following review period before closing the RCA.

Corrective Action

• Replace the failed unit and any remaining units confirmed from the same defective batch.
• Formally notify the manufacturer and pursue warranty replacement/quality corrective action for the implicated batch.
• Increase incoming inspection or FAT witnessing for future deliveries of the same product until manufacturer corrective action is verified.
• Escalate to design-for-manufacture review with the manufacturer if the issue is confirmed to stem from a marginal design rather than a one-off process lapse.

Preventive Action

• Capture manufacturer batch/production date at installation for critical components to enable faster future batch-level RCA.
• Request and review manufacturer quality escape data periodically for key product lines.
• Where volume justifies it, negotiate FAT witnessing or expanded sampling for future orders of a product line with a known quality history.
• Maintain a supplier/manufacturer quality scorecard informed by field failure RCA outcomes.

Related References

SOP: SOP-RCA-01 (Root Cause Analysis and FRACAS Procedure), SOP-QA-03 (Incoming Material Inspection Procedure), SOP-QA-04 (Supplier Quality Management)

Standards: ISO 9001:2015 Cl. 8.4/8.7/10.2, applicable FAA AC/IS product standards for the component

Diagram: Manufacturer Teardown Report and Batch Traceability Record

Case Study: Division 05 — Runway Centreline Light Troubleshooting