Mandatory frequency (MF) area

Mandatory frequency (MF): VHF frequency specified in the Canada Air Pilot or Canada Flight Supplement for radio-equipped aircraft in an MF area (CAR 101.01(1)).

Uncontrolled aerodrome:

• No control tower, or tower closed (TC AIM RAC 4.5.1).
• No controller runs traffic: pilots sequence and separate themselves. FSS, CARS, UNICOM or a vehicle operator may give information only (TC AIM RAC 4.5.1).
• Many sit inside an MF area.

MF area:

• TC designates an MF where traffic volume and mix warrant it (TC AIM RAC 4.5.4).
• Normally a circle of 5 NM radius, capped at 3,000 ft AAE (TC AIM RAC 4.5.1).
• CFS publishes frequency, distance and altitude (TC AIM RAC 4.5.4).
• MF procedures (frequency, distance, altitude to follow): CFS or Canada Water Aerodrome Supplement (CWAS) (PSTAR 3.09 key 1).

Appropriate frequency (CAR 101.01(1)), whichever applies:

• Frequency an ATS unit specifies for the pilot-in-command.
• MF at or near an aerodrome that has one.
• Otherwise, whatever the Canada Air Pilot or Canada Flight Supplement specifies for that aerodrome or airspace.

Radio equipment:

• Operating within an MF area at an uncontrolled aerodrome needs radio equipment (CAR 602.97(1)), unless CAR 602.97(3) allows.
• Applies to landing or transiting, VFR or IFR.
• CAR 602.97(3) no-radio exception: VFR flights to or from the aerodrome only, not a transit.

Listening watch:

• Radio-equipped aircraft must maintain it on the MF within the area (CAR 602.97(2)).
• After take-off, keep it until beyond the MF's published distance or above its altitude (TC AIM RAC 7.10(b), 4.5.7).

Frequency congestion stops a mandatory call (TC AIM RAC 4.5.6):

Trap: leaving the circuit does not end the watch; going beyond the published distance or above the published altitude does (TC AIM RAC 7.10(b)). A short hop through the area still needs radio equipment, unless CAR 602.97(3) applies.

Practice