Wing Bar Light

A Wing Bar Light is a versatile AGL fixture consisting of a row of lights installed perpendicular to the taxiway or runway centreline. These lights serve multiple critical functions across the airfield: they can be configured as threshold wing bars (green, marking runway thresholds on precision approach runways), stop bars (red, indicating runway holding positions), or clearance bars (yellow, providing guidance at taxiway intersections). The wing bar configuration provides a continuous visual line across the pavement, clearly defining boundaries and holding positions.

The wing bar's core purpose is to widen a single-point visual cue into a clear, unmistakable line across the pavement at exactly the location where a pilot or vehicle operator must make a decision. As a threshold wing bar, it extends the green threshold reference laterally beyond the runway edge lights, giving the pilot an unambiguous, wide visual marker of where the landing surface begins — reinforcing the touchdown judgement that runway edge and threshold lights alone can leave uncertain in reduced visibility. As a stop bar, the same physical format is repurposed as a hard visual stop signal: an illuminated red line spanning the taxiway that a pilot or vehicle driver must not cross without ATC clearance, making runway holding positions unmistakable and reducing the risk of runway incursion. As a clearance bar, the yellow configuration resolves directional ambiguity at complex taxiway intersections, confirming the correct route rather than merely marking an edge. In every configuration, the wing bar's role is the same: convert a point of critical decision-making into a full-width, colour-coded line that cannot be misread.

Wing bar lights are used in multiple applications across the airfield:

• Threshold Wing Bars: Installed on CAT II/III precision approach runways, extending outward from the runway edge lights (typically ~9–10 m beyond the edge light line, per the applicable wing bar geometry) — not measured from the runway centreline.
• Stop Bars: Installed at runway holding positions on taxiways, providing a red visual barrier to prevent unauthorized runway entry.
• Clearance Bars: Installed at taxiway intersections and holding positions, providing yellow guidance for aircraft movement.

Wing bar fixtures extend outward from the runway edge light row at the threshold, set out at 9 m either side of the extended runway edge line per the standard wing bar geometry for CAT II/III precision approach runways, using the same base can and frangible/inset mounting convention as the adjacent threshold and edge lights. Because the wing bar's role is to widen the visual cue at the threshold rather than mark a separate location, its foundations are surveyed directly off the threshold and edge light setout rather than measured independently, keeping the bar square to the runway centreline; cabling and isolating transformer arrangements follow the same series-circuit convention as the threshold lighting it extends.

Each wing bar light is powered from the series circuit via an isolating transformer. The lights project a uni-directional or bi-directional beam depending on the application, using precision optics. The colour is determined by the application: green for threshold wing bars, red for stop bars, and yellow for clearance bars. The intensity is controlled by the CCR's current steps. Wing bar lights are typically flush-mounted (inset) in the pavement to provide a low-profile installation that doesn't interfere with aircraft operations.

Wing bar lights sit on the same kind of constant current series circuit as any other AGL fixture, and the ALCMS controls them at the loop level exactly the same way — a commanded brightness step sets the current for the whole circuit, and every fixture on that loop, via its own isolating transformer, changes intensity together. What makes a wing bar a threshold marker, a stop bar, or a clearance bar is the colour filter and beam configuration built into that specific fixture, fixed at manufacture and installation — the ALCMS has no way to change a fixture's colour or beam pattern, only the shared current step for its loop. Where wing bars form part of a stop bar circuit, the on/off command itself may originate from RWSL or ground-movement logic rather than a simple ALCMS brightness schedule, but the underlying series-circuit control mechanism is unchanged.

Each fixture within the wing bar is a compact die-cast aluminium housing, machined and anodised or powder-coated for corrosion resistance, with a toughened, coloured prismatic lens (green, red, or yellow depending on the bar's function) gasket-sealed to the housing to achieve an IP67/IP68 rating. Flush-mounted units seat into an L-852 base can recessed into the pavement, load-rated for aircraft wheel loading, while elevated units bolt to a frangible coupling engineered to shear cleanly under impact, seating on a base can set flush with the surrounding grade. Because wing bar fixtures are installed in tight, closely spaced groups of three to five units, their base cans and mounting hardware are precision-positioned along a shared baseline to maintain the specified spacing and alignment across the bar. Internal wiring from each fixture terminates at L-823 sealed connectors, mating to the secondary leads of a shared or individual isolating transformer housed in a nearby base can, with stainless-steel fasteners and drainage provisions used throughout to resist corrosion and prevent water pooling around the cable entries.