AGL Component Library By Precision AGL Academy

Internally Illuminated Windsock

A fabric wind cone with an integrated light source inside the mast that illuminates the cone from within, providing clear visibility of wind direction and speed at night. Ideal for airfields where external floodlights are impractical or where unobtrusive lighting is preferred.

Internally Illuminated Windsock

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Overview

What Is It?

An Internally Illuminated Windsock is a wind cone assembly where the light source is mounted inside the mast, shining upward into the fabric cone to illuminate it from within. This design provides even, glare‑free illumination of the entire windsock, making it highly visible to pilots at night without spilling light into the surrounding area. The internal light is typically a high‑intensity LED or halogen lamp housed in a sealed, weatherproof enclosure within the mast. The cone fabric is selected for its translucency to allow light to pass through while maintaining its structural integrity and wind‑response characteristics. This type of illumination is preferred at airfields where external floodlights would cause glare, create shadows, or be aesthetically intrusive.

Purpose

Purpose & Function

Internal illumination exists to solve a specific problem external floodlighting can create: glare and light spill that either wash out the windsock's own visual pattern or intrude on surrounding areas, aircraft, or nearby communities. By lighting the cone from within, the fabric itself becomes the light source pilots see, giving a clean, evenly lit shape that's easy to read against a dark sky without the shadows or hot spots external lighting can introduce.

This matters most at locations where light discipline is a real operational concern — near residential areas, sensitive terrain, or airfields where excess ground lighting could interfere with a pilot's night vision during approach — letting the airfield keep the windsock fully visible for wind reference without adding unwanted light to the surrounding environment.

Application

Where Is It Used?

Used at airfields, heliports, and military landing zones that require 24/7 wind information without external floodlighting. Particularly common at smaller airfields, helipads, offshore platforms, and urban heliports where light pollution is a concern. Also used at fire stations and emergency helipads where a compact, self‑contained illumination system is needed. The internal illumination design is also preferred in environments with extreme weather (snow, ice) where external floodlights may be damaged or obscured.

Placement

Installation & Location

The light source is housed inside the mast head or a hoist-frame fitting at the top of the mast, shining outward through the translucent sock fabric, so the fixture and its wiring are integrated into the mast structure rather than mounted separately at ground level. Power cabling runs up through the mast in a protected conduit to the head fitting, with a weatherproof junction at the base connecting back to underground supply cable. Because the lamp or LED module sits at the top of the mast, it must be accessible for maintenance via a hinged or lowering mast head, a lightweight hoist, or an elevated platform, and any frangible coupling fitted to the mast is positioned below the lowest point of routine access so break-away function is preserved. Siting follows the same visibility and clearance requirements as the wind cone mast itself, since the two are installed as a single assembly.

Function

How Does It Work?

The internally illuminated windsock consists of a hollow mast with a lamp or LED module mounted near the top. The light is directed upward into the cone, which is made from a translucent fabric (e.g., UV‑stabilized polyester with special light‑diffusing properties). The cone material allows light to pass through evenly, illuminating the entire cone without creating hot spots. The lamp is controlled by a photocell or timer, switching on at dusk and off at dawn. An optional manual override is often provided. The mast also contains the wiring and a junction box for connection to the airfield's power supply. The swivel bearing at the top allows the cone to rotate freely with the wind, and the light source is designed to minimize shadowing while providing uniform illumination.

Architecture

System Architecture & Control Logic

Control is simpler here than for the external design because there is only one fixture to switch rather than a group of ground-level floodlights: a photocell or timer at the mast base (or in the local distribution cabinet) energises the single lamp or LED module at dusk and switches it off at dawn, with a manual override provided for maintenance and testing. Like the externally illuminated version, this circuit sits outside the CCR series loop that runs the runway and taxiway visual aids — it's a standard AC feed run up through the mast to the head fitting, not a current-stepped series circuit, so there is no intensity-step selection tied to visibility category. The trade-off for this simpler electrical picture is fault visibility: because the lamp sits at the top of an enclosed mast rather than at ground level, a failure is only obvious as "the sock has gone dark" unless the circuit's on/off and (where fitted) lamp-status signal is wired back to the ALCMS or local panel as a monitored point.

PHOTOCELL / TIMER Mast base or local cabinet — manual override available STANDARD AC FEED UP THE MAST Protected conduit — not a CCR series circuit SINGLE LAMP / LED MODULE Mast head — one fixture to switch, one to fail FAULT IS INVISIBLE UNLESS MONITORED A dark sock is the only sign, unless status is wired to the ALCMS
Light Path

Glowing From Within

Lamp Inside the Mast Shines Up Into Translucent Fabric

Light passes through the cone material itself rather than bouncing off its surface, so the whole cone glows evenly with no hot spots and no light spilling outward.

The sealed, weatherproof lamp housing sits inside the mast rather than at ground level, which is why access for maintenance is harder than on an Externally Illuminated Windsock — the payoff is glare-free, self-contained illumination that works well at urban heliports and light-pollution-sensitive sites.

Construction

Physical Construction

This configuration houses the light source inside the mast itself, shining upward through the open throat of the cone so the fabric glows from within rather than being lit externally. The lamp or LED array sits in a sealed, weatherproof fixture near the top of the mast, just below the swivel bearing, connected by wiring routed through the mast's hollow interior down to a base-mounted power supply and control gear, keeping all electrical connections protected from weather and physical damage. Because the illumination depends on light passing through the fabric, the cone material is a translucent, UV-stabilised polyester rather than the opaque fabric used on externally lit designs, selected to diffuse light evenly along the cone's length while retaining the tear strength and flame-retardant properties required for continuous outdoor service. The mast is typically powder-coated aluminium or galvanized steel, bored or fitted with an internal conduit to carry the lamp wiring, and the swivel bearing at the top is a sealed, low-friction unit that also serves as the mechanical and electrical interface between the fixed mast wiring and the rotating cone assembly.

Specification

Technical Parameters

ParameterTypical Value
Light SourceLED array (20–50 W) or compact fluorescent/halogen
Luminous Output1,000–3,000 lumens (depending on cone size)
Colour Temperature4,000–5,000 K (neutral white for colour rendering)
Cone MaterialTranslucent, UV‑stabilized polyester (flame‑retardant)
Cone Dimensions (ICAO)Truncated cone at least 3.6 m long with a throat diameter of at least 0.9 m, proportioned so it extends fully in a wind of about 15 kt and indicates direction clearly at 6 kt
Siting (ICAO)At least one indicator, visible from aircraft in flight and from the movement area, sited clear of turbulence from nearby buildings or terrain and marked by a circle 15 m in diameter where practicable
Night IlluminationAt least one wind direction indicator must be illuminated at an aerodrome intended for use at night
Cone ColourOrange and white bands (or solid orange)
Mast MaterialPowder‑coated aluminium or galvanized steel
Protection ClassIP66 / IP67 (sealed light housing)
Power Supply230V AC or 24V DC (with converter)
ControlPhotocell, timer, or manual switch
Power Supply

Electrical Requirements

RequirementTypical Value
Circuit TypeLocal mains branch circuit (230V AC) or low-voltage 24V DC via step-down converter; not part of the runway series (CCR) circuit
Swivel/Rotating ConnectionSlip-ring assembly or coiled service loop maintains the power feed to the light as the cone frame rotates with wind
Cable TypeFlexible weatherproof cable rated for the swivel/rotation duty cycle
Circuit ProtectionMCB and RCD (residual current device) at the local distribution point
Control WiringPhotocell, astronomical timer, or manual switch wired into the lighting circuit
Earthing/GroundingLight housing and mast bonded to site earth
Insulation Resistance≥ 1 MΩ (mains circuit megger test)
Standby/BackupOptional battery backup or connection to airfield emergency supply for critical sites
Optical Performance

Photometric Requirements

ParameterTypical Value
Cone Luminance (as seen from outside)Average luminance 34–103 cd/m² (10–30 foot-lamberts) per FAA AC 150/5345-27 Style I-B, measured along the fully extended cone
Minimum Point LuminanceNo point below the specified 10–30 fL (34–103 cd/m²) average band, measured at 1-foot intervals and 45° increments around the cone circumference per AC 150/5345-27
Uniformity RatioMax/min luminance ≤ 4:1 along the cone length, front to tail
Internal Light PlacementSource centred at the cone throat, directed along the axis to illuminate the full translucent length
Colour Temperature4,000–5,000 K neutral white, sufficient to distinguish orange and white bands at night
Colour RenderingCRI ≥ 70 through the fabric
Visibility DistanceCone orientation and colour bands discernible from the aerodrome traffic pattern/circuit at night
Maintenance Factor≥ 50% of commissioned luminance before lamp cleaning/replacement is due
Test MethodLuminance meter at multiple points on the cone surface, taken after dark with the cone in normal orientation
Compliance

Applicable Standards

ICAO Annex 14, Vol I — 5.1.1

Wind direction indicator: provision, location, cone dimensions and colour, and the requirement for illumination at an aerodrome intended for use at night

ICAO Doc 9157 Part 4

Aerodrome Design Manual, Visual Aids — wind direction indicator siting and marker circle guidance

FAA AC 150/5345-27

Specification for Wind Cone Assemblies — Style I-B (internally lighted) luminance test method and 10–30 fL requirement

Local electrical/building code

Governs the AC branch circuit, MCB/RCD protection, and earthing, since the lamp circuit is a standard mains installation rather than the AGL constant-current series circuit

Note on figures: the values on this page are typical reference figures drawn from the standards listed above and from manufacturers’ published data. Requirements differ between ICAO, FAA and national regimes, and between aerodrome code numbers, approach categories and equipment types. Always design, install, commission and maintain to the project specification, the manufacturer’s manual and the standard in force at the aerodrome.

Prerequisites

Installation Requirements

Mast Foundation & Frangible Coupling
Civil

Set the mast foundation and, where the site falls within a frangibility-sensitive area, fit the breakaway coupling below the lowest point of routine access.

Internal Conduit Wiring
Electrical

Route power cabling up through the mast's protected internal conduit to the head fitting, keeping wiring shielded from weather and mechanical damage.

Base Junction Termination
Electrical

Terminate the weatherproof junction at the mast base connecting the internal head wiring back to the underground supply cable.

Swivel Bearing & Head Fitting Assembly
Mechanical

Fit the sealed swivel bearing at the mast head so it serves as both the mechanical and electrical interface between the fixed mast wiring and the rotating cone assembly.

Translucent Cone Fitting
Mechanical

Fit the translucent, UV-stabilised cone fabric to the throat ring so it diffuses light evenly along its length once illuminated.

Maintenance Access Provision
Mechanical

Confirm the hinged or lowering mast head, hoist, or elevated platform is in place so the lamp fixture can be reached for maintenance.

Photocell/Timer Control Wiring
Electrical

Wire the lamp circuit through its photocell, timer, or manual switch at the base-mounted power supply and control gear.

Pre-Energisation Sign-off
Documentation

Record mast position, internal wiring route, and head fitting assembly as-built before the installation is accepted for commissioning.

Verification

Testing & Commissioning

Insulation Resistance Test
Pre-Energisation

Megger-test the lamp/LED circuit and supply cabling before the installation is energised, confirming insulation resistance clears the acceptable minimum.

Lamp/LED Circuit Continuity Test
Pre-Energisation

Verify continuity of the internal wiring from the junction box to the lamp module end to end before first energisation.

Photocell/Timer Function Test
Energisation

Confirm the photocell or timer switches the internal lamp on at dusk and off at dawn, or override correctly if manually triggered.

Internal Illumination Uniformity Test
Functional Test

Confirm the light source illuminates the cone evenly without hot spots or shadowing, checking output at the throat and tail of the cone.

Swivel Bearing Free-Rotation Check
Functional Test

Confirm the cone rotates freely on the swivel bearing and aligns correctly with wind direction without binding or drag.

Junction Box & Wiring Inspection
Pre-Energisation

Inspect the junction box and mast wiring for correct termination, sealing, and strain relief before the site is finally closed out.

Photometric Intensity Test
Final Acceptance

Measure light output through the cone fabric with a calibrated light meter against ICAO/FAA commissioning tolerances.

Documentation & As-Built Sign-off
Final Acceptance

Record insulation, continuity, and photometric readings alongside as-built position in the commissioning dossier for handover.

Upkeep

Inspection & Maintenance

Internal Light Function & Colour Check
Semi-annual

Confirm the internal LED or lamp still illuminates evenly and colour temperature stays within the neutral-white 4,000–5,000K range needed for the cone to render its orange/white bands correctly.

Cone Translucency & Condition Inspection
Quarterly

Check the cone fabric for fading, tears, or fraying, and confirm it stays sufficiently translucent for the internal light to remain visible after dark.

Photocell / Timer Control Verification
Semi-annual

Test the control method (photocell, timer, or manual switch) to confirm the internal light activates and deactivates at the correct times.

Swivel Bearing Lubrication & Function Check
Semi-annual

Lubricate the swivel bearing and confirm free rotation, since a stiff bearing gives a false wind direction reading.

Light Housing Seal Inspection
Annual

Check the sealed light housing gaskets for cracking or degradation and confirm the IP66/IP67 rating is still intact against moisture ingress inside the mast.

Mast Interior Conduit & Wiring Check
Annual

Inspect wiring routed through the hollow mast for chafing, corrosion, or moisture pooling, since this run is hidden from casual visual inspection.

Cable & Power Connection Inspection
Annual

Examine supply wiring and connectors at the base of the mast for corrosion or loose terminations, a common cause of intermittent light failure.

Mounting & Structural Attachment Check
Annual

Inspect the mast base and cone attachment points for corrosion, loosening, or fatigue from wind loading.

Field Notes

Common Field Issues

Lamp/LED Failure

The internal light source can fail, leaving the windsock unilluminated at night. Regular replacement and spare lamp availability are essential. LED modules typically last 50,000+ hours but should be tested periodically.

Moisture Ingress in Mast

Water can enter the mast through the light housing or cable entry, causing short circuits and corrosion. Regular inspection of seals and gaskets, and use of IP66/IP67 rated enclosures is critical.

Cone Fabric Translucency Degradation

UV exposure can cause the cone fabric to become opaque or discoloured, reducing internal light transmission. Regular cone replacement (every 2–3 years) is needed to maintain illumination quality.

Diagnostics

Troubleshooting Guide

Sock Goes Completely Dark at Night
Likely Cause
Failed lamp/LED module at the top of the mast, a failed photocell or timer, or an open circuit in the wiring run up through the mast — with only one fixture in this design, any of these presents the same way: total darkness.
Diagnostic Steps
Use the manual override at the mast base to test the circuit independently of the photocell/timer; check supply voltage at the base junction box; if the lamp doesn't respond to manual override with voltage confirmed present, the fault is upstream in the mast wiring or the lamp itself.
Corrective Action
Replace the photocell/timer if voltage isn't reaching the base circuit, or access the mast head via its hinged/lowering mechanism or hoist to replace the lamp/LED module; repair any open circuit found in the mast wiring run.
Sock Visible But Dim or Unevenly Lit
Likely Cause
Cone fabric has lost translucency from UV exposure and is now partially opaque, or the internal lamp/LED module is degrading rather than fully failed.
Diagnostic Steps
Inspect the cone fabric for discolouration, chalking, or opacity compared to a new cone; check lamp/LED output and hours in service against its rated life if the fabric itself looks acceptable.
Corrective Action
Replace the cone if translucency has degraded (typically every 2-3 years under UV exposure); replace the lamp/LED module if it is the source of reduced output.
Fault Not Detected Until Reported as "Sock Gone Dark"
Likely Cause
The lamp sits at the top of an enclosed mast, so unless the circuit's on/off and lamp-status signal is wired back to the ALCMS or local panel as a monitored point, a failure has no remote indication and is only caught visually.
Diagnostic Steps
Check whether a status/monitoring point exists for this fixture at the ALCMS or local panel; if none exists, confirm this against the site's monitoring scope rather than treating it as a fault.
Corrective Action
Where monitoring is expected but not working, repair the status feedback wiring; where no monitoring point was ever fitted, flag it as a gap for consideration during the next upgrade rather than a fault to fix in the field.
Water Ingress at Mast Head or Base Junction
Likely Cause
Degraded seals on the head fitting or base junction box allowing moisture to track down through the mast's protected conduit, causing corrosion or short circuits.
Diagnostic Steps
Inspect head fitting and base junction box seals and gaskets for cracking or compression set; check IP66/IP67 rated enclosures for signs of internal condensation or corrosion; megger the mast wiring if a short is suspected.
Corrective Action
Renew seals and gaskets at both the head fitting and base junction; dry out and clean any corroded connections; re-verify insulation resistance before re-energising.
Swivel Bearing Binding or Sock Not Rotating Freely
Likely Cause
Corrosion or wear in the sealed, low-friction swivel bearing that also serves as the electrical interface between the fixed mast wiring and the rotating cone assembly.
Diagnostic Steps
Observe sock behaviour in varying wind conditions to confirm it isn't tracking wind direction freely; inspect the swivel bearing for binding, corrosion, or seal failure during scheduled access.
Corrective Action
Replace the swivel bearing assembly if binding or corroded, since it carries both mechanical rotation and the electrical connection to the lamp; re-verify free rotation and lamp function together after replacement.
Frangible Coupling or Mast Access Mechanism Fault
Likely Cause
The hinged or lowering mast head mechanism, hoist, or frangible coupling has stiffened, corroded, or shifted position, complicating safe maintenance access to the lamp.
Diagnostic Steps
Test the lowering/hinge mechanism or hoist for smooth operation during a scheduled maintenance visit; confirm the frangible coupling remains positioned below the lowest point of routine access.
Corrective Action
Lubricate, repair, or replace the access mechanism as needed; correct frangible coupling position if it has shifted, to preserve both break-away function and safe access for future maintenance.
Reliability

Failure Modes & Root Causes

Lamp/LED Module Failure
High Severity
Root Cause
End-of-life failure of the internal light source at the top of the mast, despite LED modules typically being rated for 50,000+ hours.
Effect
The sock goes completely dark at night, with no other symptom to distinguish it from a wiring or control fault without further testing.
Detection Method
Manual override test at the mast base to isolate the circuit from the photocell/timer, combined with a supply-voltage check at the base junction box.
Swivel Bearing / Electrical Interface Failure
High Severity
Root Cause
Corrosion or wear in the sealed swivel bearing, which doubles as the electrical connection between the fixed mast wiring and the rotating cone assembly.
Effect
Binding or restricted rotation that prevents the sock from tracking wind direction, potentially combined with intermittent or lost illumination.
Detection Method
Observation of sock behaviour across varying wind conditions, and physical inspection of the swivel bearing for binding, corrosion, or seal failure.
Mast Wiring Open Circuit
High Severity
Root Cause
Chafing, corrosion, or a broken conductor in the wiring run up through the enclosed mast between the base circuit and the lamp.
Effect
Total loss of illumination at the sock, with the fault presenting identically to a failed lamp or control device.
Detection Method
Continuity testing of the mast wiring run once the lamp and base supply have been ruled out by manual override testing.
Cone Fabric Translucency Degradation
Low Severity
Root Cause
UV exposure over time causing the cone fabric to become partially opaque, chalky, or discoloured.
Effect
The sock appears dim or unevenly lit at night even though the internal lamp itself is functioning normally.
Detection Method
Visual comparison of the fabric's translucency against a new cone, checked against the typical 2–3 year replacement interval.
Seal or Gasket Failure (Moisture Ingress)
Medium Severity
Root Cause
Degraded seals at the mast head fitting or base junction box allowing water to track down through the mast's protected conduit.
Effect
Corrosion or short circuits within the mast wiring, which can escalate to intermittent or total loss of illumination.
Detection Method
Inspection of head fitting and junction box seals for cracking or compression set, and a megger test of the mast wiring if a short is suspected.
Frangible Coupling / Access Mechanism Fault
Medium Severity
Root Cause
Corrosion, stiffening, or positional shift of the hinged/lowering mast head mechanism, hoist, or frangible coupling over time.
Effect
Complicated or unsafe access for lamp replacement, and a frangible coupling that may no longer sit at its designed break-away point.
Detection Method
Operational test of the lowering/hinge mechanism or hoist during scheduled maintenance, and a position check on the frangible coupling.
Precautions

Safety & Operational Notes

Electrical Isolation
Electrical Safety

De-energise and lock out the internal light source supply and verify zero energy before opening the mast-top enclosure or removing the fabric cone.

Mast-Top Access
Fall Protection

The light source and its sealed enclosure sit inside the mast at the top; use fall-protection equipment and, where fitted, a lowering mechanism rather than free-climbing the mast.

Hot Lamp Handling
Personnel Safety

Allow the internal lamp to cool before handling; a sealed enclosure retains heat longer than an open external floodlight.

Enclosure Reseal
Mechanical

Reinstate the weatherproof seal on the mast-top enclosure correctly after any lamp or fabric work; a compromised seal at height is difficult to detect until moisture ingress causes a fault.

Airside Work Coordination
Operational

Coordinate with ATC/airside operations before servicing a windsock relied on for night wind indication.

PPE
Personnel Safety

Use insulated tools for internal electrical connections and fall-protection PPE appropriate to the mast height.

Restore to Compliant State
Compliance

Confirm even, glare-free illumination through the fabric and a properly resealed enclosure before closing out the work.

Field Insight

Engineering & Expert Notes

Track Cone Replacement by Fabric Condition, Not Just a Calendar
Durability

UV degradation of the translucent fabric varies significantly with local sun exposure and altitude, so a fixed 2–3 year replacement interval is only a starting point. Check actual light transmission at night during routine visits and shorten the interval for masts at high-UV sites rather than waiting for a fixed date if the fabric is visibly going opaque sooner.

Internal Heat Buildup Shortens LED Life
Thermal

An internally illuminated windsock encloses its light source inside a fabric cone with limited airflow, so heat dissipation is worse than for an open floodlight fixture. Specify LED modules with adequate thermal derating margin for the enclosed environment, and don't assume a floodlight-rated LED module will perform the same way sealed inside the mast head.

Condensation Inside the Mast is the Most Common Silent Fault
Electrical

Because the light source and wiring sit inside the enclosed mast, moisture that gets past the head seal has nowhere to evaporate and instead condenses repeatedly on the internal wiring and connections. Verify breathing/drainage provisions at the base and mast head, not just the main head seal, since a mast that seals but can't equalise pressure will trap condensation over time.

Uniformity, Not Just "Is It Lit," Is the Real Test
Commissioning

An internally illuminated sock can appear lit from the ground while actually showing a bright patch near the light source and a dim, hard-to-read tip, especially as the fabric ages unevenly. Verify illumination uniformity along the full cone length at night, not just confirm the light source is powered.

Design for Maintenance Access Before You Need It
Design

Internal lamp/LED replacement without a proper access provision at the mast head or a lowering mechanism turns a routine bulb change into a specialised, weather-dependent task. Confirm the maintenance access method at design stage, since retrofitting access onto an already-installed mast is far more disruptive than specifying it up front.

Swivel Bearing Wear Also Threatens the Electrical Path
Mechanical

On internally lit socks, the swivel bearing usually carries the power feed through to the light source, so mechanical wear here isn't purely a rotation problem — a binding or worn bearing can also stress or intermittently break the electrical connection. Treat swivel bearing inspection as an electrical reliability check, not just a mechanical free-rotation check.

Quick Answers

Frequently Asked Questions

Short answers about the Internally Illuminated Windsock: what it is, how it works, typical specifications, standards, maintenance and common faults.

Q1What is an Internally Illuminated Windsock?

An Internally Illuminated Windsock is a wind cone assembly where the light source is mounted inside the mast, shining upward into the fabric cone to illuminate it from within. This design provides even, glare‑free illumination of the entire windsock, making it highly visible to pilots at night without spilling light into the surrounding area. The internal light is typically a high‑intensity LED or halogen lamp housed in a sealed, weatherproof enclosure within the mast.

Q2What is the purpose of an Internally Illuminated Windsock?

Internal illumination exists to solve a specific problem external floodlighting can create: glare and light spill that either wash out the windsock's own visual pattern or intrude on surrounding areas, aircraft, or nearby communities. By lighting the cone from within, the fabric itself becomes the light source pilots see, giving a clean, evenly lit shape that's easy to read against a dark sky without the shadows or hot spots external lighting can introduce.

Q3Where is an Internally Illuminated Windsock used and installed?

Used at airfields, heliports, and military landing zones that require 24/7 wind information without external floodlighting. Particularly common at smaller airfields, helipads, offshore platforms, and urban heliports where light pollution is a concern. Also used at fire stations and emergency helipads where a compact, self‑contained illumination system is needed. The internal illumination design is also preferred in environments with extreme weather (snow, ice) where external floodlights may be damaged or obscured.

Q4How does an Internally Illuminated Windsock work?

The internally illuminated windsock consists of a hollow mast with a lamp or LED module mounted near the top. The light is directed upward into the cone, which is made from a translucent fabric (e.g., UV‑stabilized polyester with special light‑diffusing properties). The cone material allows light to pass through evenly, illuminating the entire cone without creating hot spots. The lamp is controlled by a photocell or timer, switching on at dusk and off at dawn. An optional manual override is often provided.

Q5What are the typical technical parameters of an Internally Illuminated Windsock?

Typical values are — Light Source: LED array (20–50 W) or compact fluorescent/halogen; Luminous Output: 1,000–3,000 lumens (depending on cone size); Colour Temperature: 4,000–5,000 K (neutral white for colour rendering); Cone Material: Translucent, UV‑stabilized polyester (flame‑retardant); Cone Dimensions (ICAO): Truncated cone at least 3.6 m long with a throat diameter of at least 0.9 m, proportioned so it extends fully in a wind of about 15 kt and indicates direction clearly at 6 kt.

Q6What are the electrical requirements for an Internally Illuminated Windsock?

Typical requirements are — Circuit Type: Local mains branch circuit (230V AC) or low-voltage 24V DC via step-down converter; not part of the runway series (CCR) circuit; Swivel/Rotating Connection: Slip-ring assembly or coiled service loop maintains the power feed to the light as the cone frame rotates with wind; Cable Type: Flexible weatherproof cable rated for the swivel/rotation duty cycle; Circuit Protection: MCB and RCD (residual current device) at the local distribution point; Control Wiring: Photocell, astronomical timer, or manual switch wired into the lighting circuit; Earthing/Grounding: Light housing and mast bonded to site earth.

Q7What photometric requirements apply to an Internally Illuminated Windsock?

Typical requirements are — Cone Luminance (as seen from outside): Average luminance 34–103 cd/m² (10–30 foot-lamberts) per FAA AC 150/5345-27 Style I-B, measured along the fully extended cone; Minimum Point Luminance: No point below the specified 10–30 fL (34–103 cd/m²) average band, measured at 1-foot intervals and 45° increments around the cone circumference per AC 150/5345-27; Uniformity Ratio: Max/min luminance ≤ 4:1 along the cone length, front to tail; Internal Light Placement: Source centred at the cone throat, directed along the axis to illuminate the full translucent length.

Q8Which standards apply to an Internally Illuminated Windsock?

The main references are ICAO Annex 14, Vol I — 5.1.1 — Wind direction indicator: provision, location, cone dimensions and colour, and the requirement for illumination at an aerodrome intended for use at night; ICAO Doc 9157 Part 4 — Aerodrome Design Manual, Visual Aids — wind direction indicator siting and marker circle guidance; FAA AC 150/5345-27 — Specification for Wind Cone Assemblies — Style I-B (internally lighted) luminance test method and 10–30 fL requirement; Local electrical/building code — Governs the AC branch circuit, MCB/RCD protection, and earthing, since the lamp circuit is a standard mains installation rather than the AGL constant-current series circuit. Always verify the current edition and your aerodrome's approved requirements.

Q9How often should an Internally Illuminated Windsock be inspected and maintained?

Typical maintenance tasks and intervals are: Internal Light Function & Colour Check (semi-annual); Cone Translucency & Condition Inspection (quarterly); Photocell / Timer Control Verification (semi-annual); Swivel Bearing Lubrication & Function Check (semi-annual); Light Housing Seal Inspection (annual); Mast Interior Conduit & Wiring Check (annual); Cable & Power Connection Inspection (annual); Mounting & Structural Attachment Check (annual). Your airport's approved maintenance programme takes precedence.

Q10How do I troubleshoot common Internally Illuminated Windsock faults?

Common symptoms covered are: Sock Goes Completely Dark at Night; Sock Visible But Dim or Unevenly Lit; Fault Not Detected Until Reported as "Sock Gone Dark"; Water Ingress at Mast Head or Base Junction; Swivel Bearing Binding or Sock Not Rotating Freely; Frangible Coupling or Mast Access Mechanism Fault. For example, for "Sock Goes Completely Dark at Night": Likely Cause: Failed lamp/LED module at the top of the mast, a failed photocell or timer, or an open circuit in the wiring run up through the mast — with only one fixture in this design, any of these presents the same way: total darkness. Diagnostic Steps: Use the manual override at the mast base to test the circuit independently of the photocell/timer; check supply voltage at the base junction box; if the lamp doesn't respond to manual override with voltage confirmed present, the fault is upstream in the mast wiring or the lamp itself. Corrective Action: Replace the photocell/timer if voltage isn't reaching the base circuit, or access the mast head via its hinged/lowering mechanism or hoist to replace the lamp/LED module; repair any open circuit found in the mast wiring run.

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