Mandatory Frequency (MF)
A Mandatory Frequency (MF) is a designated frequency at an uncontrolled aerodrome where all aircraft must monitor the frequency and broadcast their intentions and position as specified in the TC AIM. Unlike ATF aerodromes (where broadcasts are advisory), MF aerodromes require mandatory communication with a ground facility or other aircraft.
MF vs. ATF
- ATF: Self-announce only — no ground facility monitoring; frequency is shared for traffic information
- MF: A facility (FSS, CARS, or RCO relay) monitors the frequency and may provide weather and traffic information; broadcasts are mandatory
MF Procedures
- Monitor the MF before entering the MF area (typically 5 NM radius)
- Broadcast position and intentions when within the MF area
- Contact the ground station if one is monitoring — it may provide additional advisories
- MF areas and frequencies are published in the CFS
On the TC Written Exam
The distinction between MF and ATF is regularly tested. Know: MF areas have a monitoring facility; ATF areas do not. Both require broadcasts on the designated frequency.