Airport Beacon

An Airport Beacon is a rotating aviation light system installed at airports to provide a visual identification signal to aircraft. The beacon produces alternating flashes of green and white light (for land airports) or yellow and white (for water airports), with a specific flash pattern (typically 24–30 flashes per minute). The rotating assembly ensures the light is visible from all directions. The beacon is mounted on a tall structure (control tower, hangar, or dedicated mast) and is visible from up to 30–40 nautical miles in clear conditions. It is one of the most critical visual aids for pilots approaching an airport at night, providing unambiguous identification of the airfield location.

The airport beacon exists to answer the most basic question a pilot faces on a night approach before any other lighting system becomes relevant: where is the airport, and is this the correct one? Visible from up to 30–40 nautical miles, it functions as a long-range locating signal rather than a precision guidance aid, giving the pilot a confirmed heading to fly toward long before the runway's own lighting system is close enough to be useful. The green/white versus yellow/white colour distinction exists specifically so a pilot can distinguish a land airport from a water airport at that same long range, preventing a costly misidentification before the pilot has committed to an approach, which is why the beacon's colour coding is treated as safety-critical rather than merely decorative.

Installed at all civil and military airports that support night operations or low‑visibility approaches. Typically mounted on the control tower, a hangar roof, or a dedicated beacon tower at an elevated position to ensure maximum visibility. Used at land airports (green/white), water airports (yellow/white), and heliports (green/yellow/white). The beacon is often supplemented by secondary beacons at satellite terminals or remote aprons. It is one of the first lights pilots look for when locating an airfield.

Fixtures are set out at the highest practical point on the control tower, hangar roof, or a dedicated beacon tower, chosen so the rotating beam has an unobstructed 360° sweep with no nearby structures, antennas, or terrain intruding on the horizon. The mounting platform is engineered to carry the beacon's static weight plus wind and vibration loading from the rotating assembly, with a service platform or hatch built in for lamp changes and gearbox maintenance. Power and control cabling runs from the beacon controller (housed in the tower or an adjacent equipment room) up to the beacon head, with lightning protection and surge suppression fitted given the beacon's exposed, elevated position. Where a dedicated mast is used rather than an existing building, the mast is sited clear of the runway's obstacle-limitation surfaces and sized to keep the beacon above surrounding rooftops and terrain within its designed visibility radius.

The airport beacon consists of a rotating optical assembly with two or more lamps (or LED arrays) that produce alternating colours. A motor rotates the assembly at a precise speed (typically 12–15 RPM) to produce the required flash rate. The light sources are high‑intensity halogen lamps or LED modules, with coloured filters (green and white) or dichroic lenses. The beacon is powered from the airport's electrical supply, with a backup generator or UPS to ensure continuous operation during power outages. Modern beacons use LED technology for longer life, lower power consumption, and instant‑on capability. The control system includes a photocell to turn the beacon on at dusk and off at dawn, or it may be manually controlled by ATC.

The beacon fixture is the visible output of a small closed system, not a standalone circuit — the actual decision-making happens one level up, in the Beacon Controller. A photocell, timer, or ATC command decides when the beacon should run (dusk-to-dawn, or a manual override for testing). That decision reaches the controller, which is the system's single control node: it sets the drive motor's rotation speed and independently sequences the lamp or LED colours and intensity. The Drive Motor turns the optical assembly at a fixed rate to produce the required flash cadence, while the lamp path handles colour and brightness — the two outputs run in parallel but are both timed off the same controller. If mains power fails, supply to the controller transfers automatically to a UPS or standby generator, so the flash cycle continues without an interruption a pilot would notice. Fault detection runs the opposite direction: motor current draw and lamp circuit health are both monitored by the controller, and any anomaly — a stalled motor, a failed lamp, loss of rotation — is reported upstream as a fault alarm to the ALCMS rather than corrected automatically at the beacon itself.

The beacon housing is a rotating drum or fixed-optic weatherproof enclosure, typically die-cast aluminium or corrosion-resistant alloy, mounted atop a fixed pedestal or tower structure to achieve the elevation needed for 360° visibility. Twin (or single) parabolic reflector-and-lens assemblies are mounted on a precision-balanced turntable driven by the beacon motor through a gear reduction stage, with slip rings or rotary couplings carrying power and control signals across the rotating joint. The enclosure is gasket-sealed and vented to prevent condensation while achieving an IP66/IP67 weather-resistant rating, with a toughened, UV-stabilised dome or window protecting the optics from wind-driven debris and precipitation. The base structure includes lightning protection bonding, a lockable access hatch for lamp and motor servicing, and cable entry glands sealed against moisture ingress. Stainless-steel and corrosion-resistant fasteners are used throughout, given the beacon's typically exposed, elevated mounting position.