UNICOM

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UNICOM, or UNiversal Integrated COMmunication, is an air-ground communication facility operated by a private agency to provide private advisory station (PAS) service at uncontrolled aerodromes and airports with no Air Traffic Services (ATS) air-ground communication facility.

1 Description
2 Typical frequencies
3 Source
4 Note

[edit] Description

UNICOM is a communications facility for North American airports with a low volume of general aviation traffic and where no control tower is presently active. UNICOMs occur on a single communications channel or frequency. Some fields are always UNICOM while others revert to UNICOM procedures only during hours when the control tower is closed.

In this system or protocol, aircraft may call a non-government ground station to make announcements of their intentions at several defined phases of flight. In some cases, the ground station is not staffed. If no one is staffing the ground station, pilots self-announce their progress over the UNICOM channel following a standard set of phrases. For example, pilots announce at two points before they land and when they have cleared the runway after landing. When the ground station is closed, this is done without an acknowledgement from any other aircraft or ground station.

In a case where no ground station was available, the announcement after the aircraft landed and exited the runway or is landing at a runway at an airport named Binary, would be,^[1]

"Binary traffic, Cessna zero one zero uniform, clear of runway one zero, Binary."  
"Binary traffic, Luscombe foxtrot delta niner seven, entering right downwind for two seven, Binary"

Other pilots approaching or departing the field monitor the UNICOM channel. The procedure for these announcements is designed to allow pilots to understand the position of other aircraft in order to maintain safe spacing between them. The procedure calls for announcements on the ground, during departures, and when landing. The procedure calls for a series of announcements before occupying a runway and when leaving a runway or departure pattern. The pilot announces the name of the airport at the beginning and the end of the radio transmission so other pilots know which airport the transmission is from. This is especially important when two or more airports use the same UNICOM frequency in a general area. By announcing the name of the airport at the end, pilots who may not have heard it at the beginning of the transmission can confirm if the radio traffic is relevant to their operations.

UNICOM and tower-managed radio traffic are handled on the same radio frequency. This prevents pilots from landing using UNICOM (self-announce) procedures without the tower being aware of the aircraft's approach.