For 547 consecutive nights, every edge, centreline, and approach fixture on the airport's two parallel 10,500-foot runways came up at sunset and held photometric output above the 70% FAA minimum until first light. No NOTAMs. No reactive call-outs at 02:30. No 50-minute runway closures while a crew chased a ground fault through 14,000 feet of series circuit. Eighteen months. Zero unplanned outages. The airfield electrical team did not get lucky — they replaced the inspection-by-checklist culture with a CMMS-driven predictive programme that watches every isolation transformer, every megger reading, and every photometric trend line continuously. To run the same playbook on your runway, taxiway, and approach lighting infrastructure, start a free trial and load your first circuit, or book a demo to see the airfield lighting module in action.
Airfield Lighting / Runway Reliability
Zero Unplanned Runway Lighting Outages — 18 Consecutive Months
A single edge-light failure can trigger a NOTAM, force CAT II minimums down to CAT I, and cost an airport thousands per diverted aircraft. This case study shows how predictive maintenance on series circuits, isolation transformers, and photometric output kept one airport's lighting system at 100% operational availability for 547 nights running.
547
Consecutive nights with zero unplanned lighting outages
95%+
Fixture serviceability sustained for CAT II/III operations
90%
Drop in unplanned lighting outages after CMMS rollout
$220K
Annual savings from avoided closures and call-outs
Why Airfield Lighting Fails Differently Than Anything Else You Maintain
Runway lighting is a series circuit problem, not a parallel one. A single fixture loses isolation and the whole circuit can drop intensity. A constant current regulator drifts 4% out of tolerance and 200 lamps dim together below the FAA minimum. Insulation resistance falls below 1 megohm in a damp underground splice and the failure is invisible until the rain comes. Conventional checklist inspections — walk the runway, replace the dark lamps — catch failures only after they occur. The airport in this case study migrated to condition-based maintenance: monitor the leading indicators of circuit degradation, schedule intervention before output drops, and treat each isolation transformer as an individually tracked asset.
Series Circuit Topology — How One Fault Cascades
CCR
Constant Current Regulator
6.6A series output
IT
Isolation Transformer
One per fixture
FX
Edge / Centreline Fixture
LED or quartz halogen
!
One Faulted Splice
Drops circuit voltage
FX
All Downstream Fixtures
Dim or dark together
A single insulation breakdown in a 60-fixture series circuit can degrade output across every lamp on that loop simultaneously — which is why parallel-circuit thinking does not apply.
The Six Lighting Subsystems Tracked as Individual Asset Hierarchies
Treating "runway lighting" as one asset is the first cause of preventable outages. The case study airport split its airfield lighting infrastructure into six maintainable subsystems, each with its own PM frequency, spare parts kit, and degradation thresholds tied to FAA AC 150/5340-26C.
01
Runway Edge Lighting
White LED edge fixtures spaced at 200-foot intervals, fed via 5kV series circuit. PM cycles tied to photometric drift threshold of 8% below baseline. Bi-annual photometric testing per FAA AC 150/5340-26C.
02
Centreline and Touchdown Zone
Embedded in-pavement fixtures critical for CAT II/III operations. 95% serviceability threshold mandatory. Highest PM priority — quarterly photometric checks plus monthly insulation resistance monitoring.
03
Taxiway and Centreline Guidance
Blue and green centreline fixtures linking runway exits to gates. Lower priority than runway lights but high impact on ground movement throughput. Semi-annual full circuit megger testing.
04
Approach Lighting Systems
ALSF-2 or MALSR configuration extending 2,400 to 3,000 feet from runway threshold. High exposure to airframe ice fall and weather. Quarterly visual plus annual structural and photometric assessment.
05
Airfield Signage
Internally illuminated runway-holding-position and taxiway directional signs. Tied to the same series circuits as edge lighting. Monthly walkthrough inspection plus quarterly internal lamp checks.
06
Rotating Beacon and Obstruction Lights
Airport identification beacon plus FAA-mandated red obstruction lighting on towers and structures. Monthly visual confirmation, quarterly bulb and rotation mechanism check.
Six Failure Modes the CMMS Catches Before They Become NOTAMs
Every avoidable outage in 18 months traced back to one of these six degradation patterns. The CMMS turned each into a measurable signal with a threshold-triggered work order — long before the fixture went dark.
31%
Insulation Resistance Decay
Megger readings trending below 5 megohms indicate moisture ingress in underground splice cans. Once the value crosses 1 megohm, ground fault is hours away. The CMMS logs every monthly reading per circuit and triggers intervention at the 2 megohm warning band.
22%
Photometric Output Drift
LED fixtures degrade gradually — losing 8 to 12% of intensity over their first 50,000 operating hours. Drift below 70% of rated output violates FAA minimums. Bi-annual photometric scans feed trend lines that forecast replacement 12 to 18 months ahead.
17%
Isolation Transformer Failure
Each fixture has its own toroidal isolation transformer rated for ~30 years. Premature failures cluster in transformers exposed to repeated water immersion or jet blast. Asset-level PM tracks every transformer's installation date and inspection history.
14%
CCR Output Drift
Constant current regulators must hold 6.6A within ±2% across all five intensity steps. Drift beyond 4% causes uniform dimming across the entire circuit. Quarterly CCR calibration logged against manufacturer-specified output curves.
9%
In-Pavement Fixture Damage
Snow plough strikes, deicing chemical exposure, and tyre impact loosen prism assemblies and crack tempered glass. Quarterly torque-check on every in-pavement fixture catches loosening before water ingress destroys the seal.
7%
Control Panel and Firmware
Airfield Lighting Control and Monitoring System firmware drifts behind manufacturer releases. Communication faults between CCR and ALCMS show up as phantom alarms. Scheduled firmware updates and annual ALCMS audit close the gap.
Predictive Beats Reactive — Every Time
Your Lighting System Is Already Telling You When It Will Fail. Are You Listening?
OxMaint registers every fixture, isolation transformer, and CCR as an individual asset, ingests megger readings and photometric data, and creates work orders before the next NOTAM gets filed. The case study airport ran two parallel runways for 18 months without a single unscheduled lighting closure.
The Photometric Decay Curve — How LED Output Drops Below FAA Minimums
FAA AC 150/5345-46 specifies minimum photometric output for each fixture class. LEDs do not fail like incandescents — they do not go dark. They fade. The difference between a 92% output fixture and a 68% output fixture is invisible to the eye but the difference between a passing inspection and a NOTAM. The case study airport plotted output decay across its installed base and intervened at the 80% threshold, not the 70% minimum.
Photometric Output Decay vs. FAA Minimum (LED Fixture, 100,000-hr MTBF)
Year 1 — New install baseline
Year 3 — Healthy operating range
Year 6 — OxMaint intervention threshold
Year 8 — FAA minimum threshold
Year 9+ — NOTAM territory
Source: FAA AC 150/5345-46 photometric requirements, manufacturer L70 ratings for airfield-grade LED fixtures.
The Six-Step Predictive Programme That Replaced Reactive Inspections
The case study airport did not buy more inspections. It bought better data on the inspections it was already doing — then routed that data into a structured CMMS workflow that closed the loop from condition monitoring to work order completion.
1
Asset Hierarchy Build-Out
Every CCR, every isolation transformer, every fixture catalogued with make, model, install date, lumen rating, and circuit ID. Hierarchy: Airport > Runway > Circuit > Fixture > Component. 14,200 individual assets indexed in OxMaint over six weeks.
2
Condition Data Ingestion
Megger insulation readings, photometric scan results, and CCR output logs imported into OxMaint after each measurement cycle. Each value attached to the specific asset, with thresholds set per FAA AC 150/5340-26C.
3
Threshold-Triggered Work Orders
Insulation resistance below 2 megohms, photometric output below 80%, or CCR drift beyond ±3% generates an automatic work order routed to the airfield electrical lead — with the underlying readings attached as context.
4
Mobile Field Execution
Technicians complete work orders on tablet during airfield closure windows, log megger readings post-repair, photograph splice work, and update the asset record. Repair history follows each transformer and fixture for life.
5
Photometric Trend Forecasting
Bi-annual photometric scans build a per-fixture decay curve. OxMaint forecasts when each fixture will cross the 80% intervention band — typically 12 to 18 months out — and queues replacement against budget cycles.
6
FAA Audit-Ready Reporting
Every inspection, repair, and replacement timestamped with technician signature. Annual FAA Part 139 inspection prep cuts from three weeks of evidence-gathering to a one-day report export from OxMaint.
Reactive vs. Predictive — The Numbers That Drove the Business Case
The airport ran 24 months of reactive operations, then 18 months of predictive. The comparison was not subtle. Note especially the shift from emergency premium labour to scheduled crew time — emergency repairs run 4.8x the cost of planned work, and that ratio shows up everywhere in the numbers below.
| Metric |
Reactive Era (24 months) |
Predictive Era (18 months) |
Change |
| Unplanned lighting outages |
34 events |
0 events |
100% reduction |
| NOTAMs filed for lighting |
22 |
0 |
100% reduction |
| Average runway closure per outage |
52 minutes |
N/A — none occurred |
Eliminated |
| Emergency call-out labour cost |
$184,000 |
$8,400 |
95% reduction |
| Average insulation resistance trending |
Not tracked |
Logged monthly per circuit |
Full visibility |
| Fixture serviceability (CAT II/III) |
91% average |
96.4% average |
+5.4 points |
| Photometric inspections completed on time |
61% |
100% |
+39 points |
| FAA Part 139 audit prep duration |
3 weeks |
1 day |
95% reduction |
The Eighteen-Month Result — Eight Quantifiable Outcomes
When the maintenance director presented the 18-month report to the airport authority, the discussion shifted from "can we afford predictive maintenance" to "why did we wait this long". The numbers translated directly to operational reliability and budget recovery — and a substantial chunk of capex was deferred because fixtures hit their warranty L70 rating instead of failing early. To run the same playbook at your airport, start a free trial with a single circuit registered as your pilot.
547
Consecutive nights with zero unplanned outages
$220K
Annual savings from avoided closures and emergency labour
96.4%
Sustained CAT II/III fixture serviceability average
14,200
Individual lighting assets under condition tracking
95%
Reduction in emergency call-out labour spend
100%
On-time completion of photometric inspections
22 to 0
NOTAM filings related to airfield lighting
3 wks to 1 day
FAA Part 139 audit preparation time
Frequently Asked Questions
How does OxMaint integrate with existing Airfield Lighting Control and Monitoring Systems?
OxMaint reads ALCMS data via REST API or scheduled CSV export — pulling lamp outage counts, CCR output logs, and circuit fault events into asset records. The integration is read-only on the ALCMS side, so your control system remains the airfield authority, and OxMaint becomes the maintenance authority. To see how this works on a live circuit,
book a demo with our airfield specialist.
What megger and photometric thresholds should trigger work orders automatically?
Standard configuration triggers a work order when insulation resistance drops below 2 megohms (warning) or 1 megohm (critical), and when photometric output falls below 80% of rated lumens (warning) or 75% (critical, well above the FAA 70% minimum). Thresholds are configurable per circuit class to reflect CAT II/III versus CAT I requirements.
How long does asset hierarchy build-out take for a typical airport?
A medium hub with two parallel runways and a full taxiway network — roughly 12,000 to 18,000 fixtures plus CCRs and isolation transformers — takes four to eight weeks to fully ingest. OxMaint's bulk import templates and circuit auto-numbering speed the process significantly compared to manual entry per fixture.
Does OxMaint produce FAA Part 139 audit-ready documentation?
Yes. Every inspection, repair, and condition reading is timestamped, attributed to the technician who completed it, and exportable as a Part 139 compliance package. Airports using OxMaint typically reduce audit preparation from multiple weeks of evidence assembly to a single-day report export. To see the audit pack format,
start a free trial and run a sample export.
Run This Playbook on Your Airfield
Your Next Unplanned Outage Is Already Forming. Catch It Before the NOTAM.
OxMaint registers every fixture, isolation transformer, and CCR as an individual maintainable asset — ingests insulation resistance, photometric output, and regulator drift readings — and triggers work orders against thresholds set per FAA AC 150/5340-26C. The result is a runway that comes up at sunset and stays up until first light, every night, for as many nights in a row as you keep the discipline.
