Division 06 — Touchdown Zone Light Troubleshooting

01 · Touchdown Zone Light Faults

15 of 15 topics published

TDZ-206 TDZ Light Not Working

Symptom — A touchdown zone light (or a defined group) fails to illuminate when its series circuit is energised, reported via pilot report, ALCMS status, or routine night inspection.

Equipment / System

Touchdown Zone Lights (TDZ) — inset, bi-directional white L-850/L-852-style fixtures arranged in transverse light bars either side of the centreline within the touchdown zone, fed via individual isolation transformers off a dedicated TDZ series circuit, in-pavement base cans (L-867), primary series cable loop back to the CCR.

Possible Causes

HighIsolation transformer failure at the fixture (open primary/secondary winding)

HighLamp/LED source failure inside the fixture

MediumSeries circuit primary cable fault or bad connection between fixtures on the same light bar

MediumBase can or L-823 connector failure — moisture ingress, corroded pin, or plug not fully seated

LowCCR at reduced/zero output — check whether other TDZ fixtures on the same circuit are also affected

LowFixture physically damaged or displaced by jet blast, heavy braking, FOD, or vehicle strike, given the TDZ's high-wear location

Required Tools

Clamp-on series circuit ammeterTrue-RMS multimeter (CAT III)1000V insulation resistance tester (megger)Series circuit fault locator / TDRTDZ as-built circuit and base-can layout drawingBase-can lifting tool and PPE for airside work

Safety Precautions

Coordinate all airside access through ATC/airfield operations and obtain a runway closure or inspection slot before approaching the light.
Treat the series circuit as energised until confirmed isolated at the CCR and locked out.
Use FOD-safe tools and account for every item before leaving the runway strip — the touchdown zone carries the highest FOD sensitivity on the runway.

Diagnostic Procedure

ObservationCheck the ALCMS/CCR panel to see whether this is a single light or part of a wider dark bar, and confirm actual current output of the affected TDZ series circuit.
ObservationConfirm with a runway inspection whether only the reported fixture is affected or a full transverse bar / longitudinal run is also out — a single dark light with the rest of the bar lit points to that fixture; a dark bar points to the loop upstream of it.
MeasurementWith the circuit isolated and LOTO applied, disconnect the fixture's L-823 plug and megger the isolation transformer primary and secondary windings.
MeasurementInspect the base can for water, debris, or a displaced/damaged connector, and check the lamp/LED module for visible failure.
DecisionTransformer or lamp confirmed faulty at this fixture only → isolated single-fixture fault, proceed under TDZ-207. Fault traces onto the primary loop or affects multiple fixtures → treat as a circuit-level fault.
Fault LocationIsolate the fault to the fixture (transformer, lamp, connector) or to the series cable loop feeding it.
Root CauseConfirm the specific failed component before replacement rather than swapping parts speculatively.

Test Points

TDZ fixture isolation transformer (primary/secondary)

L-823 secondary connector and base can

Series cable loop, both directions from the fixture

CCR output current at the panel

Root Cause Verification

After repair, re-energise the circuit, confirm the fixture lights at all intensity steps, and inspect the full light bar at night to confirm no adjacent lights were disturbed during access.

Corrective Action

Replace the failed isolation transformer or lamp/LED module.
Reseat or replace a corroded/damaged L-823 connector.
Repair the identified series cable fault.
Restore CCR output if the root cause was upstream rather than the fixture.

Preventive Action

Include TDZ fixture and connector inspection in the routine night flight-check and periodic maintenance cycle.
Megger the series circuit periodically given the touchdown zone's heavy mechanical loading and rubber deposit exposure.
Maintain an accurate base-can and circuit layout drawing to speed fault location.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-CCR-04 (CCR LOTO Procedure)

Standards: ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46 (L-850 series)

Diagram: TDZ Circuit Layout Drawing, Base-Can Schedule

Case Study: Division 01 — CCR Troubleshooting (verify series circuit output); Division 24 — Complete Runway Lighting Failure

Rev 0 — Initial issue

TDZ-207 Multiple TDZ Lights Failure

Symptom — Two or more TDZ fixtures across one or more transverse light bars are dark or malfunctioning together, while the circuit remains energised and other bars operate normally.

Equipment / System

TDZ series circuit primary cable loop and the group of fixtures/light bars fed by the affected section.

Possible Causes

HighPrimary series cable fault between the last working fixture and the first dark one, particularly likely given repeated heavy wheel loading in the touchdown zone

HighA single failed isolation transformer developing a short circuit, collapsing available voltage to downstream fixtures on the same loop

MediumPavement distress (rutting, cracking, joint failure) in the touchdown zone damaging buried duct or cable

MediumWater ingress into a cable joint or pull box along the affected section

LowRodent or FOD damage to buried cable

LowA section isolator or field-splice left open after previous maintenance

Required Tools

Series circuit fault locator / TDR1000V/2500V insulation resistance testerClamp-on ammeterCable route and joint location drawingExcavation permit and utility locate request if digging is required

Safety Precautions

LOTO the CCR before any cable work.
Obtain excavation clearance and utility locates before opening any pavement or verge if the fault requires digging — the touchdown zone pavement structure is safety-critical and heavily loaded.
Coordinate with ATC for any extended runway occupancy needed to trace the fault.

Diagnostic Procedure

ObservationConfirm the exact extent of the dark section from a runway inspection and cross-reference against the circuit layout drawing to identify the affected cable segment(s) and light bar(s).
MeasurementWith the circuit isolated, megger the primary series cable in segments from accessible pull boxes or transformer base cans, working from each end of the affected section toward the middle.
MeasurementUse a TDR or fault locator referenced to the cable's known length to estimate fault distance if a direct segment test is inconclusive.
DecisionInsulation resistance fails on a specific segment → cable/joint fault in that segment. All segments megger clear but a specific transformer reads shorted → that transformer is loading down the loop.
Fault LocationPhysically locate and expose the faulted cable segment or confirm the single shorted transformer.
Root CauseConfirm cause of the cable fault (pavement distress, water tracking, mechanical damage) once exposed.

Test Points

Primary cable insulation resistance, segment by segment

Suspect transformer primary-to-secondary and to-earth

Pull box/joint condition along the affected run

CCR output current before and during isolation of suspect segment

Root Cause Verification

After repair, megger the full affected loop end-to-end, re-energise, and confirm all fixtures in the previously dark section illuminate correctly across all intensity steps.

Corrective Action

Repair or replace the faulted cable segment and joint.
Replace the shorted isolation transformer found to be loading the loop.
Restore any open section isolator/splice left from prior work.
Coordinate with pavement/civil teams if pavement distress is the underlying cause.

Preventive Action

Include periodic full-loop insulation resistance testing in the PM programme, trending results to catch degrading cable before failure.
Maintain accurate as-built records of every joint, pull box, and repair splice.
Monitor touchdown zone pavement condition proactively given its exposure to concentrated wheel loading.

Related References

SOP: SOP-TDZ-02 (Series Circuit Fault Location Procedure), SOP-CCR-04 (CCR LOTO Procedure)

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

Diagram: TDZ Series Circuit Route Drawing

Case Study: Division 24 — Complete Runway Lighting Failure; Division 25 — Field Case Study Troubleshooting

Rev 0 — Initial issue

TDZ-208 TDZ Light Dim

Symptom — A TDZ light illuminates but appears noticeably dimmer than adjacent fixtures in the same or paired light bar at the same commanded intensity step.

Equipment / System

TDZ fixture optical/lamp assembly, isolation transformer secondary output, and lens condition.

Possible Causes

HighLens or prism heavily contaminated with rubber deposits — the touchdown zone experiences the heaviest tyre rubber build-up on the runway

HighIsolation transformer secondary output below rated value due to partial internal fault or incorrect tap

MediumLamp/LED module degraded or nearing end of life without having fully failed

MediumIncorrect or mismatched transformer rating installed at a previous replacement

LowSeries circuit current below the correct value for the commanded step, affecting the whole loop rather than one fixture

LowLens surface abrasion from repeated tyre contact or de-icing/rubber-removal chemical exposure

Required Tools

Light output/luminance meterTrue-RMS multimeterClamp-on ammeterLens cleaning kit rated for rubber deposit removalIsolation transformer test set

Safety Precautions

LOTO the circuit before removing or cleaning a lens or accessing the fixture interior.
Allow the fixture to cool before handling if recently energised at a high intensity step.

Diagnostic Procedure

ObservationCompare the reported fixture's apparent brightness against neighbouring fixtures in the same bar at the same commanded step, ideally with a luminance meter.
MeasurementConfirm the series circuit current at the CCR matches the correct value for the commanded intensity step, to rule out a circuit-wide cause.
ObservationInspect the lens and prism for rubber deposit build-up, scratching, or degradation — touchdown zone lenses require closer scrutiny than other runway lighting given wheel contact proximity.
MeasurementWith the circuit isolated, check the isolation transformer secondary output and confirm its rated wattage/tap matches the design.
DecisionCircuit current correct and lens clean but output still low → transformer or lamp/LED degradation. Lens found heavily contaminated → clean first and re-check before replacing parts.
Fault LocationIsolate to lens contamination, transformer output, or lamp/LED degradation.
Root CauseConfirm with a before/after luminance reading once the identified cause is addressed.

Test Points

Fixture luminance output vs. neighbouring fixtures

Series circuit current at CCR

Isolation transformer secondary voltage/wattage

Lens transmission condition

Root Cause Verification

Re-measure luminance output after corrective action and compare against neighbouring fixtures and the manufacturer's rated output for the commanded step.

Corrective Action

Clean the lens and prism assembly using a rubber-deposit-rated method.
Replace an isolation transformer with an incorrect or degraded rating.
Replace a degraded lamp/LED module.
Coordinate with the runway rubber removal programme if deposits are the primary cause.

Preventive Action

Include TDZ lens cleaning in the runway rubber-removal maintenance cycle given the concentration of tyre contact in this zone.
Verify transformer rating matches the specified lamp/LED module at every replacement.
Track luminance readings over time to catch gradual degradation before it becomes a reported fault.

Related References

SOP: SOP-TDZ-03 (Lens Cleaning and Inspection Procedure)

Standards: ICAO Annex 14 Vol I (light intensity requirements), FAA AC 150/5340-30

Diagram: TDZ Photometric Specification Sheet

Case Study: Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

TDZ-209 TDZ Light Flickering

Symptom — One or more TDZ lights flicker, pulse, or vary in brightness instead of holding a steady output at the commanded intensity step.

Equipment / System

TDZ fixture, isolation transformer, connector, and the series circuit supplying it.

Possible Causes

HighLoose or intermittent connection at the L-823 connector, worsened by the vibration loading typical of the touchdown zone

HighA partially failed or overheating isolation transformer with an intermittent internal short

MediumLamp/LED driver instability or a failing LED module nearing end of life

MediumIntermittent cable fault (chafed insulation making and breaking contact) rather than a solid open or short

LowCCR output instability itself rather than a fixture-level fault

LowMoisture inside the base can causing an intermittent leakage path

Required Tools

True-RMS multimeter with min/max holdOscilloscope or power quality logger for waveform captureThermal imaging cameraL-823 connector test adaptor

Safety Precautions

Treat intermittent faults as live until proven otherwise.
LOTO the circuit before opening any base can even if the light appears steady at the time of access.

Diagnostic Procedure

ObservationConfirm whether the flicker is on a single fixture or several, and whether it correlates with a particular intensity step, aircraft touchdown/braking events, or weather condition.
MeasurementLog CCR output current over a period spanning the reported flicker to rule out a source-side instability.
MeasurementWith the circuit isolated, inspect and re-torque the L-823 connector, and megger the isolation transformer under light mechanical flexing to try to reproduce an intermittent fault.
ObservationUse thermal imaging on the connector and transformer during a live period to spot a hot connection consistent with intermittent high resistance.
DecisionFlicker follows CCR current logging → CCR/source-side issue, route to Division 01. Flicker isolated to the fixture and reproducible by flexing the connector → connector or transformer fault.
Fault LocationIsolate to the connector, transformer, lamp/LED module, or cable.
Root CauseConfirm by replacing the suspect component and re-testing under conditions that previously produced the flicker.

Test Points

L-823 connector contact resistance

Isolation transformer under mechanical flex

CCR output current trend log

Lamp/LED module bench test

Root Cause Verification

Monitor the repaired fixture over several operating cycles, including varying intensity steps, before closing out.

Corrective Action

Clean, re-grease, and properly seat the L-823 connector.
Replace a transformer confirmed to have an intermittent internal fault.
Replace a failing lamp/LED module.
Repair the identified intermittent cable fault.

Preventive Action

Torque-check connectors as a standard step in periodic maintenance, given the vibration exposure in the touchdown zone.
Include thermal imaging of connectors and transformers in the periodic PM cycle.
Trend CCR output logs to distinguish source-side from fixture-side intermittent issues early.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure)

Standards: FAA AC 150/5345-46 (L-850 series), ICAO Annex 14 Vol I

Diagram: TDZ Circuit Layout Drawing

Case Study: Division 01 — CCR Troubleshooting (intensity step control)

Rev 0 — Initial issue

TDZ-210 TDZ Light Incorrect Color

Symptom — A TDZ light shows a colour other than the specified white (e.g., an amber, discoloured, or clearly yellow-tinted output) or shows a colour inconsistent with paired fixtures across the runway.

Equipment / System

TDZ fixture lens/filter and lamp/LED module colour characteristics.

Possible Causes

HighLens discolouration/yellowing from UV degradation or heat exposure over the fixture's service life

HighWrong lamp/LED module fitted — a module of a different rated colour temperature installed by mistake at a previous replacement

MediumRubber deposit or contamination film on the lens producing an apparent colour shift

MediumLens cracked or partially melted, altering colour transmission

LowManufacturing variation between LED module batches producing a visibly different white point from neighbouring fixtures

Required Tools

Colour temperature meter (if available)Torch/inspection lightReplacement lens and correct-specification lamp/LED moduleLens cleaning kit

Safety Precautions

LOTO the circuit before removing the lens or accessing the fixture internals.

Diagnostic Procedure

ObservationConfirm the colour discrepancy visually against paired and neighbouring fixtures, and note whether it is isolated to one fixture or a wider pattern (e.g., all fixtures from one installation batch).
ObservationInspect the lens for discolouration, contamination, or damage, and clean before further diagnosis if deposits are present.
MeasurementWith the circuit isolated, confirm the lamp/LED module fitted matches the specified part number and colour temperature for TDZ fixtures.
DecisionLens discoloured/contaminated but correct module fitted → clean or replace lens. Lens clear but wrong module fitted → replace with correct-specification module.
Fault LocationIsolate to lens condition or lamp/LED module colour mismatch.
Root CauseConfirm the corrected fixture matches neighbouring fixtures' colour appearance during a night inspection.

Test Points

Lens condition and clarity

Lamp/LED module part number and colour temperature

Comparative colour appearance vs. neighbouring fixtures

Root Cause Verification

Visually confirm matching white colour appearance against the paired and adjacent fixtures during a night inspection after correction.

Corrective Action

Clean or replace the discoloured/contaminated lens.
Replace a mismatched lamp/LED module with the correct specification.
Flag a wider batch issue to the maintenance store if a colour-temperature mismatch is found across multiple fixtures from the same batch.

Preventive Action

Include lens colour/clarity checks in the periodic maintenance schedule.
Verify lamp/LED module part numbers against specification before stocking or fitting.
Source LED modules from a consistent, qualified supplier to minimise batch-to-batch colour variation.

Related References

SOP: SOP-TDZ-03 (Lens Cleaning and Inspection Procedure)

Standards: ICAO Annex 14 Vol I (Table 5-1, TDZ light colour), FAA AC 150/5340-30

Diagram: TDZ Fixture Specification Sheet

Case Study: Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

TDZ-211 TDZ Light Wrong Intensity

Symptom — One fixture, a group of fixtures, or an entire TDZ circuit displays a brightness level that does not match the intensity step commanded by the CCR/ALCMS.

Equipment / System

TDZ fixture output relative to the commanded CCR intensity step, and the isolation transformer matching that step.

Possible Causes

HighIsolation transformer of the wrong wattage/tap fitted at this fixture relative to the design

HighCCR itself outputting the wrong current for the commanded step — check whether the discrepancy affects only this fixture or the whole circuit

MediumLamp/LED module rated for a different current than the series circuit design

MediumRegulator/ALCMS step command not reaching this circuit correctly if only part of the TDZ is affected

LowLens or rubber-deposit degradation making the light appear dimmer than its actual electrical intensity (cross-check against TDZ-208)

Required Tools

Clamp-on ammeterTrue-RMS multimeterLight output/luminance meterTransformer rating reference table

Safety Precautions

LOTO the circuit before inspecting or replacing any transformer.
Confirm actual circuit current at the CCR before concluding the fault is fixture-side.

Diagnostic Procedure

ObservationConfirm the CCR is actually outputting the correct current for the commanded step, using the CCR panel/ALCMS reading cross-checked with a clamp meter if available.
DecisionIf the whole circuit is affected, route to Division 01 (CCR intensity/step control) rather than continuing at fixture level. If only one fixture or a small group is affected, continue below.
ObservationInspect the affected fixture(s) and confirm the isolation transformer wattage/tap and lamp/LED module rating against the design specification for that circuit.
MeasurementCompare luminance output of the affected fixture(s) against neighbouring, correctly-performing fixtures at the same commanded step.
Fault LocationIsolate to a mismatched transformer, mismatched lamp/LED module, or (if ruled out at fixture level) a source-side step-control issue.
Root CauseConfirm by replacing the mismatched component with the correct rating and re-measuring output.

Test Points

CCR output current vs. commanded step

Transformer wattage/tap rating

Lamp/LED module current rating

Comparative luminance vs. neighbouring fixtures

Root Cause Verification

After correction, verify the fixture's output matches neighbouring fixtures across all intensity steps.

Corrective Action

Replace the transformer with the correctly rated unit for the circuit design.
Replace the lamp/LED module with the correct current rating.
Escalate to CCR-level troubleshooting if the fault is confirmed circuit-wide.

Preventive Action

Maintain a clear parts specification/rating table at the maintenance store to prevent incorrect spares being fitted.
Verify transformer and lamp ratings as a standard check whenever a fixture component is replaced.
Include a step-by-step intensity comparison in the periodic night inspection.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-CCR-08 (Intensity Step Verification)

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

Diagram: TDZ Circuit Design Specification

Case Study: Division 01 — CCR Troubleshooting (Intensity Step Control); Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

TDZ-212 TDZ Light Beam Misalignment

Symptom — The fixture is correctly powered and optically intact, but its beam is not correctly aimed relative to the runway centreline/approach direction and the intended sightline, reducing apparent intensity from the design viewing angle.

Equipment / System

TDZ fixture mounting/levelling relative to pavement surface and the design beam elevation/azimuth.

Possible Causes

HighFixture rotated within its base can during installation or after a maintenance disturbance, changing beam azimuth

HighPavement settlement, rutting, or resurfacing changing the fixture's height/level relative to the design reference surface — a particular risk in the heavily loaded touchdown zone

MediumFixture top plate not correctly torqued, allowing rotation under repeated heavy wheel loading over time

MediumBase can itself installed off the correct offset or at an incorrect depth

LowFrangible coupling partially sheared, tilting the fixture without fully failing

Required Tools

Inclinometer/levelFixture alignment jig (if specified by manufacturer)Runway centreline/TDZ survey referenceTorque wrench for top-plate fixings

Safety Precautions

LOTO the circuit before adjusting or removing the fixture for realignment.
Coordinate any realignment work requiring fixture removal through the same airside access and runway closure process as other TDZ maintenance.

Diagnostic Procedure

ObservationConfirm the alignment issue via a night inspection from the design approach direction, comparing the affected fixture's apparent brightness against neighbours in the same bar.
MeasurementCheck fixture level/inclination against the manufacturer's specified tolerance using an inclinometer, and check azimuth orientation against the base can index/keyway if fitted.
ObservationInspect the pavement immediately around the fixture for settlement, rutting, or resurfacing overlay that may have changed the reference level — common in the touchdown zone given concentrated wheel loading.
DecisionFixture rotated/mis-torqued but base can position correct → realign and re-torque. Base can itself out of position or level → civil/installation defect requiring wider correction.
Fault LocationIsolate to fixture orientation/level within a correctly positioned base can, or to the base can/pavement reference itself.
Root CauseConfirm the corrected alignment restores the design beam pattern from the intended sightline.

Test Points

Fixture level/inclination vs. specification

Fixture azimuth vs. base can index

Surrounding pavement level/condition

Comparative apparent brightness vs. neighbouring fixtures

Root Cause Verification

Re-inspect from the design sightline at night after realignment, and confirm the fixture remains correctly oriented after the next scheduled maintenance interval.

Corrective Action

Realign and re-torque the fixture to the correct level and azimuth.
Shim or adjust the fixture mounting if pavement settlement has changed the reference level.
Escalate to civil works if the base can itself is incorrectly positioned or the touchdown zone pavement shows structural distress.

Preventive Action

Torque-check fixture top plates as part of the periodic maintenance schedule, given the elevated loading in this zone.
Coordinate with civil/pavement teams before and after any resurfacing work near TDZ fixtures to verify alignment is preserved.
Include a beam-alignment spot-check in the periodic night inspection.

Related References

SOP: SOP-TDZ-04 (Fixture Alignment Verification Procedure)

Standards: ICAO Annex 14 Vol I Appendix 2 (light beam characteristics), FAA AC 150/5340-30

Diagram: TDZ Fixture Installation and Alignment Drawing

Case Study: Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

TDZ-213 TDZ Optical Output Failure

Symptom — A TDZ light receives correct electrical power and the lamp/LED source operates, but the fixture fails to produce the correct beam pattern — light appears scattered, absent in the expected direction, or grossly asymmetric.

Equipment / System

TDZ fixture optical assembly — reflector, prism/lens system, and internal beam-forming components.

Possible Causes

HighReflector detached, corroded, or coated with condensation/contamination, scattering rather than focusing the beam

HighPrism or lens cracked, fogged, or partially melted from a previous overheating event

MediumLamp/LED module not correctly seated in its optical focal position after a replacement

MediumInternal fixture component (baffle, mounting bracket) displaced by heavy tyre-contact impact, altering the optical path

LowWrong lamp/LED module type fitted, with a different beam geometry than the fixture's optics were designed for

Required Tools

Beam pattern/goniophotometer test set (if available) or field beam-check procedureTorch/inspection lightFixture manufacturer optical assembly diagramReplacement optical components

Safety Precautions

LOTO the circuit before opening the fixture for optical inspection.
Allow the fixture to cool fully before handling the optical assembly, particularly if overheating is suspected.

Diagnostic Procedure

ObservationConfirm the light source itself is operating correctly (verify against TDZ-207/208) before concluding this is an optical rather than electrical fault.
ObservationWith the circuit isolated, open the fixture and visually inspect the reflector, prism, and lens for damage, contamination, or displacement.
MeasurementConfirm the lamp/LED module is correctly seated at the designed focal position per the manufacturer's optical assembly diagram.
DecisionPhysical damage or contamination found on optics → clean or replace the affected component. Optics appear intact but lamp/LED seating is incorrect → reseat correctly and re-check beam pattern.
Fault LocationIsolate to the reflector, lens/prism, lamp seating, or an internal displaced component.
Root CauseConfirm by a field beam-pattern check after correction, comparing against a known-good fixture of the same type.

Test Points

Reflector condition and alignment

Lens/prism condition

Lamp/LED module seating position

Comparative beam check against a known-good fixture

Root Cause Verification

Verify beam pattern visually from the design sightline (or with a goniophotometer if available) after repair, and re-inspect after several operating cycles to confirm the fix is stable under thermal and mechanical cycling.

Corrective Action

Clean or replace the reflector.
Replace a cracked or fogged lens/prism.
Reseat the lamp/LED module to the correct focal position.
Replace any displaced internal optical component.

Preventive Action

Include an internal optical inspection in the periodic deep-clean/major maintenance cycle.
Handle optical components with clean gloves during any fixture work to avoid contamination.
Use only manufacturer-approved lamp/LED modules matched to the fixture's optical design.

Related References

SOP: SOP-TDZ-05 (Optical Assembly Inspection Procedure)

Standards: FAA AC 150/5345-46 (L-850 photometric requirements), ICAO Annex 14 Vol I Appendix 2

Diagram: TDZ Fixture Optical Assembly Diagram

Case Study: Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

TDZ-214 TDZ Fixture Water Ingress

Symptom — Water is found inside the fixture housing, base can, or connector during inspection or maintenance, with or without an associated electrical fault already having occurred.

Equipment / System

TDZ fixture housing, gasket/seal system, base can drainage, and secondary connector.

Possible Causes

HighFixture top-plate gasket degraded, cracked, or incorrectly seated, allowing surface water to enter

HighBase can drainage blocked or the can itself not properly sealed to the surrounding duct/pavement — a heightened risk in the touchdown zone where surface texture and grooving concentrate runoff

MediumL-823 connector boot/seal damaged or not fully engaged

MediumFixture frangible coupling or mounting bolts loose from repeated heavy loading, breaking the seal against the top plate

LowPavement settlement or cracking around the fixture allowing surface water to track directly into the base can

LowCondensation accumulation from thermal cycling rather than external ingress

Required Tools

Insulation resistance tester (1000V/2500V)Wet/dry vacuum for base-can pump-outReplacement gaskets, seals, and connector bootsTorque wrench for top-plate fixing bolts

Safety Precautions

LOTO the circuit before opening a fixture or base can with standing water.
Do not assume a wet fixture is de-energised; test with a rated meter before hand contact.
Dispose of pumped-out water per site environmental procedure if contamination is suspected.

Diagnostic Procedure

ObservationConfirm the extent of water ingress — fixture housing only, base can, or both — and note whether any electrical fault (dim, dark, flickering) is already present.
MeasurementWith the circuit isolated, megger the fixture and transformer to confirm whether insulation has already been compromised.
ObservationInspect the top-plate gasket, connector boot, and base-can seal/drainage for the specific ingress path, checking grooved pavement runoff patterns typical of the touchdown zone.
DecisionInsulation resistance already low → treat as an active electrical fault, replace affected components before re-energising. Insulation resistance still acceptable → address the sealing issue and monitor.
Fault LocationIsolate the specific ingress path — gasket, connector boot, base-can seal, or drainage blockage.
Root CauseConfirm the fixture and base can are fully dry and re-test insulation resistance before closing out.

Test Points

Insulation resistance, fixture to earth

Insulation resistance, transformer to earth

Top-plate gasket condition

Base-can drainage function

Connector boot integrity

Root Cause Verification

Re-test insulation resistance after drying and resealing, and re-inspect the fixture after the next significant rainfall to confirm the ingress path has been fully resolved.

Corrective Action

Replace the degraded top-plate gasket.
Clear or restore base-can drainage.
Replace the damaged connector boot/seal.
Torque the top-plate fixing bolts to specification.
Pump out and dry the base can fully before closing up.

Preventive Action

Include gasket and seal condition in the periodic maintenance checklist, replacing proactively rather than only on failure.
Check and clear base-can drainage as part of routine maintenance, especially before the wet season, given the touchdown zone's grooved-pavement runoff.
Track fixtures with a history of water ingress for targeted remediation.

Related References

SOP: SOP-TDZ-06 (Water Ingress Response Procedure)

Standards: FAA AC 150/5345-46 (L-850 environmental sealing requirements), ICAO Annex 14 Vol I

Diagram: TDZ Base-Can and Gasket Detail Drawing

Case Study: Division 25 — Field Case Study Troubleshooting

Rev 0 — Initial issue

TDZ-215 TDZ Fixture Mechanical Damage

Symptom — The fixture body, top plate, or frangible coupling is found physically damaged — cracked, deformed, or partially sheared — typically from heavy aircraft wheel loading during touchdown, braking, or reverse-thrust events, or from vehicle/snow equipment contact.

Equipment / System

TDZ fixture housing, top plate, and frangible mounting coupling.

Possible Causes

HighRepeated heavy aircraft wheel loading during normal touchdown operations, cumulatively fatiguing the fixture housing or top plate — the touchdown zone experiences the highest mechanical loading of any inset light on the runway

HighFrangible coupling activated (as designed) by an aircraft wheel load exceeding its threshold, or by a heavy vehicle exceeding the coupling's intended load path

MediumDirect impact from a snow plough blade, sweeper, or other airside vehicle passing over or too close to the fixture

MediumCorrosion-weakened housing failing under normal operational loading

LowManufacturing or installation defect in the housing or coupling

Required Tools

Visual inspection kitTorque wrench and fixture-specific toolingReplacement fixture body/frangible coupling assembly, correct part numberBase-can lifting tool

Safety Precautions

LOTO the circuit before removing a damaged fixture.
Treat a sheared frangible coupling as having potentially left live conductors exposed at the base can — verify de-energised and inspect carefully before further handling.
Coordinate FOD sweep of the immediate area after fixture damage, given the elevated FOD risk in the touchdown zone.

Diagnostic Procedure

ObservationDocument the extent and apparent cause of physical damage, photographing for the maintenance and incident record.
MeasurementWith the circuit isolated, check the condition of the base-can wiring and connector, since fixture damage often accompanies connector or cable disturbance.
ObservationConfirm whether the frangible coupling has functioned as designed (clean shear at the intended break point) or whether damage extends into the base can itself.
DecisionFrangible coupling sheared cleanly, base can and wiring intact → straightforward fixture replacement. Damage extends to base can or wiring → treat as a more extensive repair.
Fault LocationIsolate the damage to the fixture body/top plate, the frangible coupling, or damage extending into the base can.
Root CauseWhere damage appears to be from cumulative wheel loading rather than an isolated event, note the failure pattern for possible fixture specification review given the touchdown zone's duty cycle.

Test Points

Frangible coupling condition — clean break vs. extended damage

Base-can wiring and connector integrity

Insulation resistance post-damage

Surrounding pavement/FOD condition

Root Cause Verification

After fixture replacement, confirm correct electrical operation (megger and functional test) and correct alignment before returning the section to service, and complete an FOD sweep of the area.

Corrective Action

Replace the damaged fixture body and/or frangible coupling assembly.
Repair any base-can wiring or connector damage found.
Realign the replacement fixture per TDZ-212 as part of the installation.

Preventive Action

Investigate recurring fixture damage on a given fixture position for a specification, installation, or pavement-condition cause given the elevated duty cycle in the touchdown zone.
Maintain fixture and frangible coupling spares on hand given the touchdown zone's higher expected replacement frequency.
Include frangible coupling condition in the periodic visual inspection.

Related References

SOP: SOP-TDZ-07 (Fixture Replacement Procedure), SOP-TDZ-08 (Frangible Coupling Inspection)

Standards: FAA AC 150/5345-46 (L-850 frangibility requirements), ICAO Annex 14 Vol I

Diagram: TDZ Fixture and Frangible Coupling Assembly Drawing

Case Study: Division 27 — FOD & Physical Damage Case Studies

Rev 0 — Initial issue

TDZ-216 TDZ Connector Failure

Symptom — The L-823 secondary connector between the isolation transformer and the fixture (or between the primary cable and the transformer) is found failed — corroded, cracked, arced, or not maintaining a reliable connection.

Equipment / System

L-823 primary and secondary connectors within the TDZ base can.

Possible Causes

HighWater ingress into the connector body leading to corrosion and increased contact resistance

HighConnector not fully mated or seated during a previous installation or maintenance visit

MediumConnector boot/seal perished or damaged, allowing moisture and contamination in over time

MediumArcing damage from a marginal connection that has been carrying current under partial contact for an extended period, aggravated by the touchdown zone's vibration exposure

LowWrong connector type or rating fitted, mismatched to the cable/fixture combination

LowPhysical damage to the connector body from being pinched or crushed during base-can work

Required Tools

L-823 connector test adaptor1000V insulation resistance testerDielectric greaseReplacement connector, correct type and ratingTorque/crimp tool as specified by connector manufacturer

Safety Precautions

LOTO the circuit before disconnecting or inspecting any connector.
Treat a connector showing arc/heat damage as a sign of a fault that may have been present for some time — inspect adjacent components for related damage before re-energising.

Diagnostic Procedure

ObservationWith the circuit isolated, open the base can and visually inspect the connector for corrosion, cracking, arc marks, discolouration, or an incompletely mated condition.
MeasurementMegger across the connector and check continuity/contact resistance if a suitable test adaptor is available.
ObservationInspect the connector boot/seal for damage and check whether water was present in the base can (cross-reference TDZ-214).
DecisionConnector shows corrosion/arc damage or fails a contact-resistance check → replace. Connector appears sound but was simply not fully mated → reseat correctly with fresh dielectric grease and re-test.
Fault LocationIsolate to the primary-side or secondary-side connector, and to the connector itself versus the boot/seal.
Root CauseConfirm the corrected connection holds under a follow-up inspection, particularly after the next significant rain event if water ingress was implicated.

Test Points

Connector contact resistance/continuity

Insulation resistance across the connector

Boot/seal condition

Base-can water presence

Root Cause Verification

Re-test insulation resistance and contact integrity after reconnection, and schedule a follow-up check after the next wet-weather period to confirm the seal is holding.

Corrective Action

Replace the failed connector with the correct type and rating.
Reseat and re-grease a connector found simply mismated.
Replace a perished boot/seal even if the connector body itself is serviceable.

Preventive Action

Apply dielectric grease at every connector mating as standard practice.
Include connector contact-resistance checks in the periodic maintenance programme, at a tighter interval than lower-loading divisions given the touchdown zone's vibration exposure.
Stock the correct connector types and boots as standard spares.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-TDZ-09 (Connector Maintenance Procedure)

Standards: FAA AC 150/5345-26 (L-823 connectors), ICAO Annex 14 Vol I

Diagram: TDZ Base-Can Wiring Detail Drawing

Case Study: Division 25 — Field Case Study Troubleshooting

Rev 0 — Initial issue

TDZ-217 TDZ Transformer Failure

Symptom — The individual isolation transformer feeding a TDZ fixture has failed — open-circuit, short-circuit, or significantly out of tolerance on secondary output — distinct from a fixture lamp/LED or connector fault.

Equipment / System

TDZ series-circuit isolation transformer (typically 30W/45W/65W class, matched to the fixture's lamp/LED rating).

Possible Causes

HighWinding failure from age-related insulation breakdown, particularly in transformers exposed to repeated water ingress

HighInternal short circuit from moisture tracking across the windings

MediumThermal damage from prolonged operation at a mismatched (too high) wattage rating for the fitted lamp/LED module

MediumPhysical/impact damage to the transformer body or leads during base-can work

LowManufacturing defect or a transformer that was already marginal at installation

LowCascading damage from a nearby lightning strike or major surge event on the series circuit

Required Tools

1000V/2500V insulation resistance testerTrue-RMS multimeterClamp-on ammeterReplacement transformer, correct wattage/tap ratingBase-can lifting tool

Safety Precautions

LOTO the circuit before disconnecting or removing any transformer.
Handle a transformer suspected of internal arcing carefully — do not assume it is fully de-energised even after the circuit is isolated, until tested.

Diagnostic Procedure

ObservationConfirm via CCR/ALCMS and a runway inspection that the fault pattern (single dark light, no downstream effect on the loop) is consistent with a fixture-level transformer fault rather than a cable fault (cross-reference TDZ-207).
MeasurementWith the circuit isolated, disconnect the transformer at both primary and secondary connectors and megger primary-to-earth, secondary-to-earth, and primary-to-secondary.
ObservationInspect the transformer body for physical damage, discolouration, or evidence of internal arcing/overheating.
MeasurementConfirm the transformer's wattage/tap rating matches the design specification for the fitted lamp/LED module.
DecisionTransformer fails insulation test or shows physical damage → replace. Transformer tests good but wattage/tap mismatched → replace with correctly rated unit even though the current one has not fully failed.
Fault LocationConfirm the transformer itself as the fault, distinct from the connector (TDZ-216) or fixture lamp/LED (TDZ-207/208).
Root CauseBench-test the removed transformer if practical to confirm the specific failure mode for the maintenance record.

Test Points

Transformer primary winding insulation resistance

Transformer secondary winding insulation resistance

Primary-to-secondary insulation resistance

Transformer wattage/tap vs. design specification

Root Cause Verification

After replacement with the correctly rated transformer, re-energise and confirm the fixture operates correctly across all intensity steps, and re-check insulation resistance at the next scheduled maintenance visit.

Corrective Action

Replace the failed transformer with a correctly rated unit.
Correct a wattage/tap mismatch even where the existing transformer has not yet fully failed.
Address any water ingress found in the base can (cross-reference TDZ-214) to prevent recurrence.

Preventive Action

Include transformer insulation resistance testing in the periodic PM programme, trending results to catch degrading units before failure.
Verify wattage/tap rating against the design specification at every transformer replacement.
Maintain correctly rated transformer spares on hand.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-TDZ-10 (Transformer Test and Replacement Procedure)

Standards: FAA AC 150/5345-26 (L-823/isolation transformers), ICAO Annex 14 Vol I

Diagram: TDZ Circuit Design Specification

Case Study: Division 01 — CCR Troubleshooting (series circuit fundamentals)

Rev 0 — Initial issue

TDZ-218 TDZ Cable Failure

Symptom — The primary series cable feeding a TDZ light bar or circuit segment shows a confirmed insulation or conductor fault, distinct from a single transformer or connector failure, requiring cable-level repair or replacement.

Equipment / System

TDZ primary series cable (typically 5 kV or 8.3 kV rated, per the CCR loop design) and its route through ducts, pull boxes, and base cans within the touchdown zone.

Possible Causes

HighInsulation breakdown from age, moisture tracking, or cumulative thermal cycling under load

HighMechanical damage from pavement works, heavy vehicle loading, or duct crushing during resurfacing in the touchdown zone

MediumA degraded or improperly made field splice/joint failing under load or moisture exposure

MediumRodent damage to cable insulation in accessible duct sections

LowManufacturing defect or an original installation with an undersized bend radius causing insulation stress over time

Required Tools

1000V/2500V/5000V insulation resistance tester as appropriate to cable ratingSeries circuit fault locator / TDRCable route and joint location drawingExcavation permit and utility locate request if digging is requiredCable splicing kit rated for the cable class

Safety Precautions

LOTO the CCR before any cable testing or repair work.
Obtain excavation clearance and utility locates before opening any pavement or verge.
Treat a suspected cable fault as potentially live at both ends until the CCR is confirmed isolated and the cable is independently verified dead.

Diagnostic Procedure

ObservationConfirm from circuit-level symptoms (dark section, TDZ-207) and prior fault-location work that the fault is confirmed to be in the cable itself rather than a fixture or connector.
MeasurementMegger the cable in accessible segments from pull boxes or base cans, and use a TDR/fault locator to pinpoint distance to fault along the identified segment.
ObservationOnce physically exposed, inspect the cable and any joints for the specific failure mode — insulation breakdown, mechanical damage, or a failed splice.
DecisionDamage isolated to a short section → repair by splice. Cable degraded over an extended length or of an age/condition warranting it → replace the full segment rather than repeated spot repairs.
Fault LocationConfirm the precise fault location by physical exposure before cutting or splicing.
Root CauseDetermine and record the failure mode (age, mechanical damage, joint failure) to inform whether adjacent cable sections need proactive attention.

Test Points

Cable insulation resistance by segment

TDR distance-to-fault reading

Splice/joint condition at exposed points

Duct condition along the route

Root Cause Verification

After repair, megger the full repaired segment and the adjoining sections, re-energise, and confirm all fixtures on the loop operate correctly across all intensity steps.

Corrective Action

Repair the cable by a correctly rated splice where damage is localised.
Replace the full cable segment where damage or age warrants it.
Restore duct protection where mechanical damage was the cause.

Preventive Action

Include periodic insulation resistance testing and trending of TDZ series cable in the PM programme, given its critical-zone location.
Coordinate closely with civil/pavement teams before any excavation or resurfacing near known TDZ cable routes.
Maintain accurate as-built cable route and splice records.

Related References

SOP: SOP-TDZ-02 (Series Circuit Fault Location Procedure), SOP-TDZ-11 (Cable Splice and Repair Procedure)

Standards: IEC 60502 (power cable), ICAO Annex 14 Vol I, FAA AC 150/5340-30

Diagram: TDZ Series Circuit Route Drawing

Case Study: Division 24 — Complete Runway Lighting Failure

Rev 0 — Initial issue

TDZ-219 TDZ Circuit Intermittency

Symptom — A TDZ circuit or a section of it exhibits an intermittent fault — lights that fail and recover unpredictably, or a circuit that trips/alarms sporadically — without a fault being reliably reproducible during a single inspection.

Equipment / System

TDZ series circuit as a whole, spanning cable, connectors, transformers, and CCR interaction, where the fault does not present consistently.

Possible Causes

HighA marginal cable insulation fault that only breaks down under specific moisture or thermal conditions

HighA marginal connector connection that opens and closes under vibration or thermal expansion, particularly given the touchdown zone's mechanical loading

MediumA transformer with an intermittent internal fault that only manifests under certain load or temperature conditions

MediumA CCR-side issue (protection relay marginally set, or a control fault) that intermittently affects this circuit — verify against Division 01 before assuming a field-side cause

LowEnvironmental correlation (rain, temperature swing, specific aircraft operations) not yet identified because the pattern has not been systematically logged

Required Tools

Data logger for trend/repeated-event analysis1000V/2500V insulation resistance testerSeries circuit fault locator / TDRCCR alarm/event log export toolWeather/environmental log for correlation

Safety Precautions

LOTO the circuit before any physical inspection, even though the fault is intermittent and the circuit may appear to be operating normally at the time of access.
Coordinate extended monitoring periods with ATC/airfield operations if data logging equipment needs to remain connected across multiple shifts.

Diagnostic Procedure

ObservationSystematically log every reported occurrence — date, time, weather, and which fixtures/sections were affected — to identify a pattern before attempting physical fault-finding.
ObservationReview the CCR/ALCMS alarm and event log for any correlation with protection trips, voltage dips, or other circuit-level events coinciding with reported occurrences.
MeasurementInstall a data logger on the circuit to capture current, and if possible individual fixture status, across a period likely to include a recurrence.
DecisionOccurrences correlate with a specific condition (rain, temperature, time of day) → target inspection and testing under that condition. No clear correlation → proceed to a full systematic megger and connector check of the circuit during the next available access window.
Fault LocationNarrow the intermittent fault to a specific cable segment, connector, or transformer using correlation data and, where possible, testing that reproduces the fault condition (e.g., mechanical flexing, controlled wetting of a suspect joint).
Root CauseConfirm the specific component once identified by isolating and testing it independently, ideally under the condition that previously triggered the fault.

Test Points

CCR/ALCMS alarm and event log

Circuit current trend log across a monitoring period

Suspect connectors under mechanical flex

Suspect cable segments under simulated wetting, if safe and appropriate

Root Cause Verification

After the suspected component is repaired or replaced, continue monitoring across at least one full cycle of the previously identified correlating condition (e.g., a rain event) before closing out.

Corrective Action

Repair or replace the specific component identified through correlation-based testing.
Escalate to CCR-level investigation if the intermittency is confirmed to originate at the source rather than in the field.

Preventive Action

Maintain a structured fault log for all TDZ circuits to make future intermittent-fault correlation faster.
Include a periodic full-circuit megger test as standard, since it is often the only way to catch a marginal insulation fault before it becomes a reported outage.
Review connector torque and transformer condition preventively given the touchdown zone's elevated vibration environment.

Related References

SOP: SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-TDZ-02 (Series Circuit Fault Location Procedure)

Standards: ICAO Annex 14 Vol I, IEC 60364

Diagram: TDZ Circuit Layout Drawing

Case Study: Division 22 — Intermittent Fault Methodology; Division 25 — Field Case Study Troubleshooting

Rev 0 — Initial issue

TDZ-220 TDZ Photometric Non-Compliance

Symptom — A TDZ light or group of lights, while electrically and mechanically functional, fails to meet the required photometric output (intensity, beam spread, or colour coordinates) when measured against ICAO/FAA standards during a compliance survey.

Equipment / System

TDZ fixture photometric performance as measured against ICAO Annex 14 Appendix 2 / FAA AC 150/5340-30 specifications for touchdown zone lighting.

Possible Causes

HighCumulative lens contamination (rubber deposits, general grime) reducing transmitted intensity below the compliance threshold across multiple fixtures

HighAggregate fixture ageing (lamp/LED lumen depreciation) across a section approaching or past its rated service life

MediumA batch of fixtures with a systematic transformer wattage or lamp/LED mismatch installed during a previous bulk replacement

MediumBeam alignment drift across multiple fixtures due to pavement settlement in the touchdown zone (cross-reference TDZ-212)

LowSurvey/measurement methodology or equipment calibration issue producing an apparent non-compliance that does not reflect the true fixture output

Required Tools

Calibrated mobile photometric survey unit or handheld luminance/intensity meterColour coordinate measurement equipmentICAO/FAA photometric compliance reference tablesFixture and transformer inventory records

Safety Precautions

LOTO the circuit before any fixture-level intervention following the survey.
Conduct photometric surveys per the applicable procedure and calibration schedule to ensure results are valid before acting on them.

Diagnostic Procedure

ObservationConfirm the survey methodology and equipment calibration are valid before treating the result as a genuine fixture-level non-compliance.
ObservationIdentify whether non-compliance is isolated to specific fixtures, a specific installation batch, or the section generally, by cross-referencing survey results against the fixture/transformer inventory and installation dates.
MeasurementPhysically inspect a representative sample of the non-compliant fixtures for lens contamination, lamp/LED condition, transformer rating, and beam alignment.
DecisionNon-compliance traces to contamination → clean and re-survey before replacing components. Non-compliance traces to aged lamps/LEDs or a batch mismatch → plan targeted or bulk replacement. Isolated to alignment → route to TDZ-212.
Fault LocationIsolate the dominant contributing cause (contamination, ageing, mismatch, alignment) across the affected fixtures.
Root CauseConfirm compliance is restored with a follow-up photometric re-survey after corrective action.

Test Points

Measured intensity vs. ICAO/FAA minimum for each surveyed fixture

Beam spread and colour coordinates vs. specification

Lens condition across the affected sample

Fixture/transformer age and specification records

Root Cause Verification

Conduct a follow-up photometric survey of the corrected fixtures, and cross-check a sample of unaffected neighbouring fixtures to confirm the survey and correction are consistent.

Corrective Action

Clean lenses across the affected section as a first step where contamination is implicated.
Replace lamp/LED modules that have reached end-of-life lumen depreciation.
Correct a transformer/lamp mismatch found across an installation batch.
Correct beam alignment on fixtures affected by pavement settlement.

Preventive Action

Schedule photometric compliance surveys on a defined recurring interval rather than only reactively.
Track fixture installation dates and expected lumen-depreciation curves to plan proactive replacement before compliance margins are lost.
Verify transformer/lamp specification consistency across every bulk fixture procurement or replacement batch.

Related References

SOP: SOP-TDZ-12 (Photometric Compliance Survey Procedure)

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

Diagram: TDZ Photometric Specification Sheet

Case Study: Division 26 — Photometric & Intensity Compliance

Rev 0 — Initial issue

No topics match your search. Try a different term.

Frequently Asked Questions

Quick answers about Touchdown Zone Light (TDZ) troubleshooting in the AGL Troubleshooting Atlas.

Q1What does Division 06 of the AGL Troubleshooting Atlas cover?

Division 06 is the Touchdown Zone Light (TDZ) Troubleshooting reference. It publishes 15 diagnostic topics, TDZ-206 to TDZ-220, for Touchdown Zone Light (TDZ) faults on airfield ground lighting systems.

Q2What information does each topic include?

Every topic follows the same diagnostic record: the symptom, equipment/system, possible causes ranked by likelihood (high, medium or low), required tools, safety precautions, diagnostic procedure, test points, root cause verification, corrective action, preventive action and related references (SOPs, standards, diagrams and case studies).

Q3Which Touchdown Zone Light (TDZ) faults are covered?

The 15 topics are TDZ-206 to TDZ-220: TDZ Light Not Working; Multiple TDZ Lights Failure; TDZ Light Dim; TDZ Light Flickering; TDZ Light Incorrect Color; TDZ Light Wrong Intensity; TDZ Light Beam Misalignment; TDZ Optical Output Failure; TDZ Fixture Water Ingress; TDZ Fixture Mechanical Damage; TDZ Connector Failure; TDZ Transformer Failure; TDZ Cable Failure; TDZ Circuit Intermittency; TDZ Photometric Non-Compliance.

Q4How does a diagnostic procedure begin in Division 06?

Each procedure starts with observation before any intervention. For example, TDZ-206 (TDZ Light Not Working) begins: Check the ALCMS/CCR panel to see whether this is a single light or part of a wider dark bar, and confirm actual current output of the affected TDZ series circuit.

Q5What safety precautions apply when troubleshooting Touchdown Zone Light (TDZ)?

Each topic lists its own precautions. For example, TDZ-206 (TDZ Light Not Working) starts with: Coordinate all airside access through ATC/airfield operations and obtain a runway closure or inspection slot before approaching the light.

Q6Which SOPs are referenced in Division 06?

Related references in the topics include SOP-TDZ-01 (TDZ Fault Isolation Procedure), SOP-CCR-04 (CCR LOTO Procedure), SOP-TDZ-02 (Series Circuit Fault Location Procedure), SOP-TDZ-03 (Lens Cleaning and Inspection Procedure), SOP-CCR-08 (Intensity Step Verification), SOP-TDZ-04 (Fixture Alignment Verification Procedure), SOP-TDZ-05 (Optical Assembly Inspection Procedure) and SOP-TDZ-06 (Water Ingress Response Procedure), and 6 more.

Q7Which standards are referenced in the Touchdown Zone Light (TDZ) topics?

Where a standard applies, it appears in the topic's Related References. Those cited in this division include ICAO Annex 14 Vol I, FAA AC 150/5340-30, FAA AC 150/5345-46, IEC 60364, ICAO Annex 14 Vol I Appendix 2, FAA AC 150/5345-26 and IEC 60502.

Q8How can I find a specific fault in Division 06 quickly?

Use the search box at the top of the page to filter the 15 published topics by code, fault name or keyword; matching topics open automatically. Each diagnostic record can also be downloaded as a Word (.doc) file.