Primary Frequency

A primary frequency is the main radio frequency assigned for communication between a pilot and an ATC unit or FSS. When communication is established on the primary frequency, all subsequent communications in that sector or area are normally conducted on that frequency unless a frequency change is specified.

Primary vs. Guard Frequency

121.5 MHz is the international distress and guard frequency — monitored by all but used for emergency communications. Primary frequencies are sector-specific working frequencies listed in the CFS and on en route charts. Always use the assigned primary frequency for normal communications; use 121.5 only for emergencies or when primary contact fails.

Related Terms

See also: Discrete Frequency, Broadcast, Mayday.