Good question Dan. It's a common misconception that a CTAF is an volume of airspace surrounding an aerodrome.That is not correct. As the name implies, a CTAF (common traffic advisory frequency) is a radio frequency that is used by aircraft in the vicinity of an aerodrome.

I guess it is due to the requirement to give an inbound call by 10nm that people get the idea that 10nm is some kind of boundary. There is no such thing as a CTAF boundary since it is not a defined piece of airspace and lateral and vertical limits do not apply.

Years ago CTAFs were actually marked on ERC charts with boundaries around the aerodromes and I suspect that that may be where the misconception began. The recommended 10nm inbound call is flexible, note that the AIP actually says you should call [b][i]by[/i][/b] 10nm, not [b][i]at[/i][/b] 10nm. [i]AIP ENR 1.1 para 10.5.7.[/i]

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Thank you Bob, that clears that one up for me. Appreciate your help.

Dan.

[quote="Dan" post=9077]Thank you Bob, that clears that one up for me. Appreciate your help.

Dan/Bob,
To my understanding yes a CTAF is a radio frequency and not an airspace classification as per Class C or Class D etc . However , I do think of “CTAF AREA “( or MTAF AREA) - surrounding a specific airfield using that designated frequency and so actually as a volume of space - in which the CTAF designated to that area needs to be used for radio calls for plane separation, position awareness to other pilots in the same area ect. . I have dated books. advising a CTAF “area” is 5nm radius by 3000 ft AAL and a MTAF ( Mandatory Traffic Advisory Freqyency) area is 15nm radius by 5000ft above arerodrome level (AAL). Are these dimensions still valid ? Further, am I right in thinking if I’m not in that space then I do not have to listen in or broadcast on that frequency eg as in the case of flying over an airfield on route to elsewhere?

It is true that actual dimensions were once given for the so-called CTAF AREA. In fact they once actually marked CTAFs on ERC charts with a boundary on the chart (MTAFs no longer exist). That is no longer the case. You should adopt CTAF procedures and make CTAF calls if you consider that your distance/height makes you relevant traffic to that aerodrome. Specific aerodromes may require consideration of different distances/heights. The simple rule is 'if in doubt - make the call',