MFAs and ATF areas


Judging from the number of CADORS involving Mandatory Frequency Areas and Aerodrome Traffic Frequency Areas over the past year there appears to be some misunderstanding in the aviation community as to the rules governing them.

A Mandatory Frequency Area (MFA) is established at airports where there is a Flight Service Station (FSS) or Community Air Radio Station (CARS). These are airports that have Class "E" control zones because they have instrument approaches, but are uncontrolled (no control tower).

A two-way radio is required to operate in a Class "E" control zone unless prior permission has been granted to operate on the airport or in the control zone without a radio.

The radius and top of the control zone will be depicted graphically in the Canada Fight Supplement (CFS). The radius of a Class "E" control zone will typically be 5 statute miles and it will be capped at 3,000 feet.

An Aerodrome Traffic Frequency (ATF) Area is established at active uncontrolled airports where there is no FSS or CARS. There may be a UNICOM operator on the airport to provide limited information. The ATF will be listed in the CFS along with the dimensions of the ATF Area.

An ATF Area may also be established as an extension to a regular ATF Area or in a busy corridor between two ATF Areas. These extensions and corridors will be listed in the CFS.

A C-172 taxied on and departed from an airport without establishing radio contact with the FSS.

Two C-172 aircraft taxied on Taxiway "C" and crossed the active runway without establishing radio contact with the FSS.

A Robinson R22 entered the control zone and landed without establishing radio contact with the FSS.

A DHC 6 Twin Otter entered a harbour control zone in weather conditions below VFR without contacting the FSS for a Special VFR clearance. Another aircraft was on an instrument approach to the harbour at the time.

A Cessna 414 entered the runway without requesting an airport advisory.

Two C-172 aircraft arrived at an airport with an ATF at about the same time. One of the pilots flew a mid-field crossing and joined the circuit for a landing. The second pilot flew a straight in approach to the same runway. Both aircraft were broadcasting their intentions over the radio. Unfortunately, the first pilot was broadcasting on the wrong frequency. He did not switch from 126.7. The second pilot was on the correct ATF. Neither pilot was aware of the other, but assumed that they would hear other traffic broadcasting if there was other aircraft in the area. The two aircraft collided on final approach. Amazingly, all 3 persons on board the 2 aircraft survived.

A C-177 Cardinal was climbing out from runway 34. A Mooney 20C had been low flying over a nearby community and decided to join the circuit for runway 34 by flying through the departure path of the runway. Both pilots were communicating with the FSS specialist at the airport, but the Mooney pilot did not clearly state his intentions. All four persons on board the two aircraft died when the two aircraft collided.

Pilots must transmit the following on the appropriate frequency in, or around, an MFA or ATF Area:

  • intentions before entering a manoeuvring area (taxiway);
  • departure intentions before moving onto the runway;
  • before taking-off;
  • departing from the circuit;
  • when clear of the MF area;
  • before entering the MF area, and where possible 5 minutes before entering the MF area, giving the aircraft position, altitude, estimated time of arrival at the aerodrome, and the arrival procedure intended;
  • on joining the circuit and position;
  • on downwind;
  • on final approach;
  • when clear of the runway;
  • when flying continuous circuits - joining the downwind leg, on final with pilot's intentions and clear of the runway after landing; and
  • when flying through an MF area - before entering the MF area, and where possible five minutes before entering the MF area, giving the aircraft position, altitude and pilot's intentions, and when clear of the MF area.

Pilots must remain clear of an MFA until contact with the FSS or CARS has been established.

All of these calls update your position and intentions to other aircraft and to the FSS specialist or CARS operator so that they may include you in their advisories to other aircraft and to vehicles working on the airport.

When an FSS specialist or CARS operator know your intentions, he/she will issue instructions for vehicles to clear a taxiway or runway. It is easier to see another aircraft if you know where to look. It is also important to know where IFR aircraft are in relation to the airport, especially on cloudy days. An IFR aircraft may descend out of cloud above the traffic pattern or onto final approach.

Special VFR must be requested and cleared before entering a Class "E" control zone. This clearance is issued by ATC through the FSS specialist or CARS operator. An SVFR clearance will not be issued to enter a control zone or to depart an airport with a control zone if there is an aircraft on approach or about to depart the airport.

No radio (NORDO) and receive only (RONLY) aircraft must receive prior permission to operate at an MFA airport. NORDO and RONLY aircraft must fly at least two legs of the traffic pattern before turning onto the final approach path.

It is important to make all of the mandatory radio calls on the correct frequency and to state where you are and what your intentions are. Failure to do so may be fatal.

Dale Nielsen is an ex-Armed Forces pilot and aerial photography pilot. He lives in Abbotsford, B.C., and currently flies air charters. He still freelances as a flying instructor and seminar facilitator. Nielsen is also the author of seven flight training manuals published by Canuck West Holdings.

Got an aviation safety story to tell? Dale Nielsen would like to hear from pilots who have educational aviation experiences to relate. Excerpts from these stories will be used in upcoming safety articles. Dale can be contacted via e-mail: