The dedicated failure classification for illuminated airfield signs — covering the complete failure path from LED/light-source and electrical failures through optical performance, enclosure/environmental condition, structural condition, message integrity and vehicle-impact damage. LED module failure, LED driver failure, sign outage, uneven illumination, low brightness, incorrect colour, moisture ingress, seal failure, mounting failure, sign misalignment, message/component damage, corrosion and vehicle-impact damage.
Key principle — A sign being electrically energized does not necessarily mean that it is operationally satisfactory. A sign may remain ON while suffering from uneven illumination, low brightness, incorrect colour, message damage, optical degradation or structural misalignment. Every record should distinguish cause, component failure, performance failure and service-level failure, so the database does not record only the final symptom.
Failure of one or more LED modules used to illuminate the airfield sign.
Check:
Failure of the electronic driver supplying or controlling the LED modules.
Trace: Power supply → driver → LED modules → optical output.
Complete loss of required illumination of the airfield sign.
Check the complete electrical path: Supply → protection → wiring → driver → LED modules.
"Complete sign outage" is the service-level failure, while the underlying cause should be recorded separately.
Loss of illumination from part of an otherwise functioning sign.
Identify:
Illumination across the sign face is visibly or measurably non-uniform.
Compare: Illuminated area → dark/bright areas → module condition → driver condition → optical condition.
Sign illumination is present but brightness is below the expected/required level.
Complete outage: no required illumination. Partial outage: some illumination areas unavailable. Low brightness: illumination remains but is insufficient. Uneven illumination: brightness distribution is inconsistent. These should remain separate failure categories.
The illuminated sign displays a colour that is incorrect, degraded or outside the required appearance/performance.
Check:
Failure of wiring or internal electrical connections within the airfield sign.
Check:
Failure of connectors associated with the airfield sign.
Cross-reference with Division 05 — Cable & Connector Failures.
Loss or abnormality of the electrical supply required for airfield-sign operation.
Trace: Source → protection → cable → connector → sign power supply → driver → LED module.
Entry of moisture into the airfield sign enclosure or electrical/optical components.
Inspect:
Cross-reference with Division 09 — Environmental Failures.
Failure or deterioration of the sealing arrangement intended to protect the sign enclosure from environmental exposure.
Cross-reference with Division 08 where improper installation is established.
Damage to the physical enclosure/housing of the airfield sign.
Inspect:
Damage to the structural elements supporting or forming part of the airfield sign.
Failure of the mounting arrangement that secures the sign in its intended position.
Check:
The airfield sign is no longer positioned/oriented as required.
Compare: Actual orientation → approved layout/design → required viewing direction.
Damage to the sign message, legend, face, panel or associated physical component that affects the intended sign information.
The message itself should be treated as a functional element of the sign, not merely cosmetic artwork.
Corrosion of sign housing, structure, hardware, electrical interfaces or other metallic components.
Excessive temperature within the sign or its components resulting in degradation or failure.
Check:
Damage to the airfield sign caused by vehicle contact or impact.
A vehicle-impact inspection should cover:
Cross-reference with Division 06 — Mechanical & Structural Failures and Division 10 — Operational Incidents.
Standard record structure, failure chains, classification and diagnostic layer that apply across all 20 Division 12 airfield-sign-failure topics.
For every sign failure, capture the following fields, grouped by identification, technical condition, optical/functional condition, environmental/physical condition, RCA, corrective action, verification and reliability:
Division 12 should specifically capture the failure chain, because one sign failure can lead to another, and the final symptom is rarely the whole story.
These relationships become extremely valuable when Division 12 is later connected to the Root Cause Analysis Database and Reliability & Failure Trend Analysis.
The 20 topics are organised into four logical groups while retaining the original numbering:
This gives Division 12 a complete airfield-sign reliability structure — not only whether the sign is ON/OFF, but whether it is properly illuminated, bright, uniform, correctly coloured, physically intact, correctly aligned and capable of conveying the intended operational information.
Every failure receives a severity classification, plus operational-impact tagging:
Critical / Safety-Critical — immediate operational or safety risk
Major / Operationally Critical — significant availability impact
Moderate — reduced performance, not yet critical
Minor / Non-Critical — limited or no operational effect
Degradation / Intermittent / Latent — developing or hidden fault
Each of the 20 topics maps to a primary investigation focus — e.g. LED module failure → LED/module condition, complete sign outage → complete supply/illumination path, vehicle-impact damage → complete impact assessment. This keeps every record anchored to a repeatable diagnostic starting point.
Division 12 distinguishes between cause, component failure, performance failure and service-level failure so the database does not record only the final symptom. Example: vehicle impact (cause) → housing damage + mounting failure (physical failure) → sign misalignment (position failure) → reduced visibility (functional consequence) → airfield sign unavailable/ineffective (operational consequence). A sign that is electrically energized is not necessarily operationally satisfactory — uneven illumination, low brightness, incorrect colour, message damage, optical degradation and structural misalignment can all coexist with a sign that appears "ON".
Quick answers about illuminated airfield sign failures, as covered in Division 12 of the AGL Failure Database.
Division 12 covers failures of illuminated airfield signs. It contains 20 published topics (ASF-01 to ASF-20) spanning LED module and driver failure, sign outage, illumination and colour performance, enclosure and environmental condition, structural condition, message integrity and vehicle-impact damage.
LED module failure, LED driver failure, complete and partial sign outage, uneven illumination, low brightness, incorrect colour, internal wiring failure, connector failure, power-supply failure, moisture ingress, seal failure, housing damage, structural damage, mounting failure, sign misalignment, message/component damage, corrosion, overheating and vehicle-impact damage.
They fall into four groups while keeping the original numbering: Illumination & Electrical Failures (10 topics), Environmental & Enclosure Failures (4), Structural & Mechanical Failures (4) and Thermal & Impact Failures (2).
No. A sign that is electrically energised is not necessarily operationally satisfactory. Uneven illumination, low brightness, incorrect colour, message damage, optical degradation and structural misalignment can all coexist with a sign that appears to be ON.
Division 12 distinguishes cause, component failure, performance failure and service-level failure so the database does not record only the final symptom. For example, a vehicle impact (cause) leads to housing damage and mounting failure (physical failure), then sign misalignment (position failure), reduced visibility (functional consequence) and an airfield sign that is unavailable or ineffective (operational consequence).
In the LED chain, LED module failure leads to partial sign outage, uneven illumination, reduced readability and operational impact. In the driver chain, LED driver failure leads to LED output loss, complete sign outage and an unavailable sign. Moisture chains starting from seal failure are also captured.
Records cover identification (failure ID, airport, location, sign identification and type, date/time, circuit or asset reference), failure category and mode, LED, driver and power-supply condition, optical and functional condition, environmental and physical condition, RCA, corrective action, verification and reliability.
Every failure receives a severity classification, plus operational-impact tagging. The classes are Critical / Safety-Critical (immediate operational or safety risk), Major / Operationally Critical (significant availability impact), Moderate (reduced performance, not yet critical), Minor / Non-Critical (limited or no operational effect), and Degradation / Intermittent / Latent (a developing or hidden fault).
Internally illuminated signs fail from driver faults, panel delamination, moisture ingress and connector corrosion — real troubleshooting means understanding sign construction and electrical supply well enough to fix the actual cause, not just the symptom.
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