Bidirectional / Omnidirectional Runway Edge Fixture

A Bidirectional/Omnidirectional Runway Edge Fixture is a runway edge light that offers selectable or fixed light distribution patterns to suit different operational requirements. In bidirectional mode, the fixture projects light in two opposite directions along the runway centreline, visible to pilots approaching from either end. In omnidirectional mode, the fixture emits light uniformly in all directions (360°), providing edge visibility from any angle — particularly useful at runway intersections, curved sections, or where aircraft may be positioned at various angles on the runway. This dual‑capability fixture reduces the need for separate inventory of bidirectional and omnidirectional lights, simplifying maintenance and logistics for airfield operators.

A standard runway edge light assumes pilots only ever approach from one predictable direction and angle; the bidirectional/omnidirectional fixture exists for the geometries where that assumption breaks down. Its purpose is to eliminate the dark or ambiguous edge segments that would otherwise appear wherever a runway is operated from both ends, where taxiways or rapid-exit turns intersect the edge line at an angle, or where a curved section or displaced threshold puts the pilot's viewing angle outside a single fixed beam's coverage. By projecting a correctly coloured beam — white along the runway body, yellow in the final 600 m / 2,000 ft (or half the runway length, whichever is less) on instrument runways — toward every direction from which an aircraft can legitimately approach or occupy that point, the fixture preserves continuous, correctly coded lateral guidance exactly where a single-direction light would leave a gap. This also serves an operational purpose beyond the individual light: because one fixture design covers both bidirectional and omnidirectional roles, airfield operators can standardise on fewer part numbers, simplifying stock holding and reducing the chance of an incorrect fixture being installed at a critical, non-standard location.

This versatile fixture is used on runways where both approach directions are operational, requiring bidirectional visibility, as well as at runway intersections, rapid exit taxiway turnoffs, and curved sections where omnidirectional visibility is beneficial. It is also suitable for runways with displaced thresholds, where edge lights need to be visible from multiple angles. The fixture is available in both elevated (frangible pole) and inset (flush‑mounted) configurations, making it suitable for all runway pavement types. It is used on precision and non‑precision instrument runways, with white light output for the main runway section and yellow (amber) for the last 600 m (2,000 ft), or half the runway length if less, on runways where this caution zone applies.

Fixtures are set out along the runway edge at standard spacing using an elevated frangible-mount base can or an inset base can depending on pavement type, positioned no more than 3 m outward from the runway edge and clear of the graded strip's load-bearing width, the same convention as other runway edge lights. Because the fixture must switch from white to yellow over the final 600 m (or half the runway length, whichever is less) on runways where this caution zone applies, setout for that section is tied precisely to the runway centreline survey measured back from the runway end, so the colour transition point lines up exactly across both edge rows rather than drifting between the two sides; cabling and isolating transformer arrangements otherwise follow the standard runway edge lighting series circuit.

The fixture contains an optical system that can be configured for bidirectional or omnidirectional output. In bidirectional mode, a precision prism and reflector system directs light into two opposite narrow beams (typically 3° vertical × 6° horizontal each), aligned along the runway centreline. In omnidirectional mode, a diffuse reflector or multifaceted prism spreads the light uniformly in all horizontal directions (360°) with a controlled vertical spread (3°–6°). Some designs allow field‑adjustable optics to switch between modes, while others are fixed at manufacture. The light source is typically a high‑output LED array or halogen lamp, powered by the series circuit via an isolating transformer. Intensity is controlled by the CCR's current steps, with 5‑step (2.8A – 6.6A) operation. The frangible coupling (elevated version) or rugged housing (inset version) ensures safety and durability.

Control-wise, this fixture behaves exactly like a standard runway edge light — it is not individually addressable, and its optical mode (bidirectional or omnidirectional) has no bearing on how it is controlled. An ALCMS command selects a brightness step, the CCR regulates the entire series circuit loop to the corresponding fixed current, and every fixture on that loop draws the same current through its own isolating transformer and burns at the same intensity at the same moment. Whether a given unit is configured for two opposing narrow beams or a 360° diffuse spread is a fixed (or field-set) property of its internal optics, decided at installation rather than commanded at runtime, so it plays no part in the loop's control logic. A loop fault — an open circuit or a failed transformer — is detected the same way as on any other series circuit, through a voltage rise at the CCR relative to the commanded current, and is reported at the loop level rather than pinned to one fixture without further sectionalised testing.

This fixture is built on the same die-cast aluminium housing platform as a standard runway edge light, but with an optical assembly configured for either a bidirectional or omnidirectional light distribution. Bidirectional units house two separate lamp and lens assemblies within the housing, angled back-to-back so each projects its beam along the runway centreline in opposite directions, with the housing and internal wiring sized to accommodate the additional light source. Omnidirectional units instead use a single light source paired with a specially shaped reflector or diffusing lens that spreads the beam through a full 360° horizontal arc, trading peak beam intensity for all-round visibility. In both configurations, the optical assembly is gasket-sealed behind a hardened glass or polycarbonate lens to achieve an IP67/IP68 rating, and the fixture mounts on the same frangible coupling and L-867 base can, or L-868 inset can, arrangement as a standard edge light. Internal wiring terminates at sealed L-823 connectors feeding the isolating transformer in the base can, and stainless-steel fasteners and corrosion-resistant coatings are used throughout consistent with the rest of the runway edge lighting family.