AGL Cable Duct for Airfield Lighting Cable Routing

An AGL cable duct is a defined pathway that helps protect AGL electrical cables from mechanical damage and supports an organised underground cable network. It is suitable for runway and taxiway crossings and can interface with junction pits and handholes, with cable capacity selected according to circuit requirements.

Ducts are used at runway crossings, taxiway crossings, underground AGL cable routes and field electrical infrastructure, and cable approaches to junction pits and handholes. They apply to new airfield lighting installations, runway and taxiway rehabilitation, and protected routes through areas subject to mechanical loading.

Duct materials commonly include rigid steel conduit, PVC and HDPE, usually concrete-encased under pavement. The material is selected according to the application, and the designer confirms it against loading, ground conditions and the airport specification.

Dimensions are selected from the number, size and type of cables, leaving sufficient space for installation without excessive mechanical stress on the cables and for future maintenance. Provide spare ducts for future cable additions and replacement, and where future expansion is anticipated consider the duct as part of the overall cable-routing strategy.

Crossings need particular attention to mechanical loading, installation depth and protection of the cable route. The duct configuration should be coordinated with the pavement construction, finished surface level, required installation depth, expected loading, cable quantity and diameter, crossing length, drainage conditions and existing underground services. Under runways, taxiways and aprons, concrete-encase the duct or follow the approved pavement-crossing detail, and follow the approved civil and electrical design.

Depth depends on the location, surrounding infrastructure and applicable project requirements. Relevant considerations are pavement thickness, cable requirements, crossing loading, duct construction, ground conditions, existing underground services, drainage and finished surface elevation. The selected depth should give the required protection while remaining compatible with the surrounding infrastructure.

Keep cable bends within the cable's minimum bending radius, using sweeps instead of tight elbows, and slope ducts toward junction pits or handholes so water drains away from the crossing. Segregate series-circuit cables from control, communication and other service cables as the design requires, and provide spare ducts for future additions.

Treat existing AGL cables in or near the duct route as energised until proven isolated, and confirm routes from as-built drawings and a cable locator before excavation. Install a pull line in each duct and clear debris before cable pulling, check pulling tension and sidewall pressure against the cable manufacturer's limits, and seal duct ends and unused ducts to limit water, soil and rodent ingress. Keep earthing or counterpoise continuity across the crossing where the design requires it, and record route, depth and duct allocation on as-built drawings and the cable schedule.

Ducts connect to accessible underground infrastructure such as junction pits and handholes, which provide access for cable routing, inspection, jointing, circuit maintenance, testing and future cable replacement. Position and seal duct entries appropriately to maintain cable protection and prevent damage during installation.

Yes. Cable ducts apply to both new AGL infrastructure and airport rehabilitation projects. For replacement or rehabilitation work, assess existing cable routes, duct conditions, pavement construction and available access points before selecting the new configuration, and where existing ducts are retained, verify their condition and capacity against the proposed cable installation.

Inspect accessible duct infrastructure as part of relevant airfield electrical maintenance, looking at duct condition, cable protection, cable entry points, junction interfaces, evidence of water ingress, mechanical damage, blockages or obstructions, and compatibility with installed cables. Assess any damaged or obstructed section before additional cable installation.

References may include ICAO Doc 9157 Part 5 (Electrical Systems), FAA AC 150/5340-30J, FAA AC 150/5370-10 Items L-110 (underground electrical duct banks and conduits) and L-115 (electrical manholes and junction structures), pavement design and civil standards for the crossing, Indian Standards for the selected duct material, and DGCA requirements and the airport authority project specification.

Confirm the cable type, quantity and diameter, required capacity, crossing or route location, required installation depth, expected mechanical loading, duct dimensions and material, junction pit or handhole locations, drainage conditions, existing underground services and applicable project requirements. Dimensions, material, loading, installation depth and cable capacity should be confirmed for the specific runway, taxiway or field installation.