An aerodrome beacon, airport beacon, rotating beacon or aeronautical beacon is a beacon installed at an airport or aerodrome to indicate its location to aircraft pilots at night.
An aerodrome beacon is mounted on top of a towering structure, often a control tower, above other buildings of the airport. It produces flashes similar to that of a lighthouse.
Airport and heliport beacons are designed in such a way to make them most effective from one to ten degrees above the horizon; however, they can be seen well above and below this peak spread. The beacon may be an omnidirectional flashing xenon strobe, or it may be an aerobeacon rotating at a constant speed which produces the visual effect of flashes at regular intervals. Flashes may be of one, two, or three alternating colors (described below).
*Green alone or yellow alone is used only in connection with a white-and-green or white-and-yellow beacon display, respectively.
**Military airport beacons flash alternately white and green, but are differentiated from civil beacons by two quick white flashes between the green flashes.
In Class B, C, D, and E surface areas, operation of the airport beacon between sunrise and sunset often indicates that the ground visibility is less than 3 miles and/or the ceiling is less than 1,000 feet. This is true particularly at locations where beacon controls are available to air traffic control personnel;[2] however there is no regulation requiring daytime operation.[1]
At some locations with operating control towers, ATC personnel turn the beacon on or off with controls in the tower. At many airports the airport beacon is turned on by a photoelectric cell or time clocks, and ATC personnel cannot control them.[1]
In Canada
In Canada, the regulations are different. Lighted aerodromes are equipped with white single flash beacons operating at a frequency of 20 to 30 flashes per minute. Heliports with beacons exhibit the morse letter H (4 short flashes) at a rate of 3 to 4 groups per minute.[3]
