Intermediate Holding Position Light

An Intermediate Holding Position Light is a specialized taxiway lighting system that marks intermediate holding positions on taxiways where aircraft may be required to stop and await clearance. These lights provide visual guidance to pilots at holding points that are not at runway intersections, typically indicating positions where aircraft hold before crossing active taxiways or entering critical areas. The lights are typically a combination of yellow/amber fixtures that define the holding position boundary, helping pilots to accurately position their aircraft and maintain safe separation from other traffic.

Intermediate holding positions exist away from runway intersections, at points where taxiways cross each other or where an aircraft must wait before entering a busy or restricted area — situations that carry real collision risk even though no runway is involved. The purpose of this light is to give that non-runway holding point the same kind of definite, visible stopping reference a pilot gets at a runway holding position, so ground traffic can be sequenced safely without relying purely on radio calls and markings.

Intermediate holding position lights are installed at various locations on the airfield where holding is required: Intersecting taxiways where holding is required before crossing Approaches to active runways (intermediate holding positions) ILS critical area boundaries where holding is required Apron entry/exit points where traffic flow is managed Maintenance and construction zones where temporary holding is required Complex taxiway layouts requiring intermediate holding points.

Intermediate holding position lights operate as part of the taxiway guidance system: Power: Powered from the constant current series circuit via an isolating transformer (typically 15W – 45W). Light Source: Utilizes yellow/amber LED arrays or yellow-filtered halogen lamps. The yellow colour indicates a holding position that is not runway-related. Configuration: Typically installed as a row of lights (3 to 5 fixtures) across the taxiway at the holding position.

Typical values are — Light Source: Yellow/Amber LED array or 15W – 45W halogen with yellow filter; Colour: Yellow/Amber (holding position indicator); Luminous Intensity: 100 – 500 candela (depending on setting); Intensity Steps: 3 to 5-step (2.8A – 5.2A) CCR controlled; Configuration: Row of 3-5 lights across taxiway; Beam Pattern: Uni-directional or omnidirectional; Mounting Type: Elevated (frangible) or Inset (flush); Load Capacity (inset): Rated for in-pavement aircraft wheel loading per FAA AC 150/5345-42; base-can bolts torqued per FAA Engineering Brief 83A; Isolating Transformer: 15W – 45W (6.6A series circuit); Protection Class: IP67 / IP68 (submersible).

Typical requirements are — Circuit Type: Series circuit, constant current (CCR fed); Rated Series Current: 5.2A / 6.6A (3 to 5-step: 2.8A – 5.2A); Isolation: Via dedicated isolating transformer (15W/45W), not directly connected to series loop; Transformer Secondary: Matched to fixture wattage; sized to series circuit rating; Cable Type: L-824 single-conductor, direct-burial rated, 5kV or 600V per circuit design; Connector: L-823 primary connector, submersible-rated splice; Insulation Resistance: ≥ 50 MΩ (megger test, cable-to-ground); Earthing/Grounding: Fixture body and base can bonded to airfield earth grid.

Typical requirements are — Main Beam Intensity (100%): ≥ 100 cd (yellow/amber) per ICAO Annex 14 / IEC TS 61827; Intensity Steps (3–5 step): 100% / 30% / 10% / 3% / 1% of rated peak intensity; Vertical Beam Spread: Main beam 2°–10° above horizontal (peak ~3°–4°); Horizontal Beam Spread: Uni-directional: ± 5° either side of taxiway centreline; omnidirectional variants distribute 360°; Isocandela Distribution: Per ICAO Annex 14 Attachment A / FAA AC 150/5345-46 figures for holding position lights; Chromaticity (Yellow): Within ICAO Annex 14 yellow boundary (CIE coordinates); Maintenance Factor: ≥ 50% of new-fixture intensity before replacement/cleaning is due.

The main references are ICAO Annex 14 — Intermediate holding position light requirements and placement standards; FAA AC 150/5345-46 — Specification for intermediate holding position lights; IEC TS 61827 — Electrical and photometric performance for AGL luminaires; FAA AC 150/5345-53 — Airport Lighting Equipment Certification Program. Always verify the current edition and your aerodrome's approved requirements.

Typical maintenance tasks and intervals are: Photometric Intensity Check (annual); Lens & Filter Cleaning (quarterly); Row Alignment Check (semi-annual); Frangible Coupling / Housing Inspection (annual); Seal & Gasket Inspection (annual); Insulation Resistance Test (annual); Cable & Connector Inspection (annual); Base / Pavement Inspection (annual). Your airport's approved maintenance programme takes precedence.

Common symptoms covered are: Single Fixture Dark, Rest of Row Normal; Entire Row Dark / CCR Will Not Regulate; Row Fails to Respond to ALCMS On/Off Command; CCR Trips on Overcurrent or Ground Fault; Reduced or Discoloured Yellow/Amber Output; Row Misaligned With the Holding-Position Marking. For example, for "Single Fixture Dark, Rest of Row Normal": Likely Cause: Failed LED array/lamp, or an open isolating transformer (blown primary fuse-wire link or failed secondary winding). Diagnostic Steps: Confirm series loop continuity through the fixture's transformer primary; megger the transformer; check secondary voltage at the L-823 connector with the CCR energised. Corrective Action: Replace the LED array/lamp if the transformer checks healthy; otherwise swap the isolating transformer and re-seal the L-823 connectors before backfill.