I'm looking at St-Frédéric airport in Quebec, Canada (CSZ4) and specifically at the "COMM" section. It says that there is an Aerodrome Traffic Frequency (ATF) on 122.8 but it also seems to say that you need to contact Montreal Centre (135.025) on arrival and departure:

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Does this mean that Montreal Centre is to be contacted only when the ATF (UNICOM) is not operating, or do I have to contact it at all times?

  • 1
    $\begingroup$ Since rules vary by country and the question referenced Montreal, I added the Canada tag. $\endgroup$ – Gerry May 6 '18 at 11:40
  • $\begingroup$ Can you link to or quote the text you're looking at? $\endgroup$ – Pondlife May 7 '18 at 0:20
  • $\begingroup$ I've added a screenshot from the Canada Flight Supplement. $\endgroup$ – faridghar May 7 '18 at 5:19
  • $\begingroup$ I'm not familiar with the CFS, but what are you seeing that makes you think it might be mandatory to contact APP/DEP? In the US, the frequencies are shown just in case you need them. $\endgroup$ – Pondlife May 7 '18 at 18:22
  • $\begingroup$ I'd have to check other ATF aerodromes to see if they also list centre frequencies but I can't say I've seen this before. Maybe it has something to do with the proximity of this aerodrome to Quebec's class C airspace. $\endgroup$ – faridghar May 7 '18 at 18:43

The Aerodrome Traffic Frequency is a frequency for aircraft to use to aid self-sequencing at airports where a control tower is not operational. Another name for it is the Common Traffic Advisory Frequency. 122.8 MHz was the original frequency designated for UNICOM use and remains one of the more common ones.

The APP/DEP frequencies listed tell pilots that, if they desire to talk with ATC (as IFR flights probably would!), they need to contact Montreal Centre on 135.025 once airborne. Montreal Centre is also the arrival frequency that would help IFR arrivals get established on an instrument approach procedure, if one existed. Centre most probably does not have radio coverage to the ground on this frequency, and even if they did they would not provide towered-airport control services.


Its a mandatory frequency airport which means that aircraft are supposed to notify center when they arrive or depart.

  • $\begingroup$ Do you have a reference for that requirement? I couldn't find it in the CARs or the AIM. $\endgroup$ – Pondlife May 7 '18 at 2:42
  • $\begingroup$ I couldn't find that requirement either. In fact transport canada (section 4.5.7) just says you have to contact the MF/ATF on arrival and departure. It also says that if the ground station (UNICOM in this case) is not in operation, then all reports should be broadcast. There is not moention of contacting centre. $\endgroup$ – faridghar May 7 '18 at 5:18
  • $\begingroup$ Your link says that arriving and departing must communicate through the published frequency their position and intentions. It does not require those communications to be with Center or even ATC. This only differs from other Class G airports by the requirement for communication. Normally, Class G without a control tower does not require a pilot to make radio calls. In the US, radio calls in uncontrolled airspace is only very strongly recommended and encouraged, but not required. $\endgroup$ – Dean F. Mar 31 at 14:53

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