Hi Guys. I know that the AIP states that broadcast is mandatory prior to 10nm from a CTAF, but it also says that for transiting flights, broadcast should be made if transiting at an altitude likely to affect local traffic. I cannot find anywhere that gives any guidance as to what this altitude should be? I seem to recall in the old MBZ's broadcast was mandatory if transiting below 5000' AGL.

At what altitude would you consider it safe to maintain a listening watch rather than congesting the 126.7 frequency with transiting calls for CTAFs? I ask because on longer cross country flights, even in sparse WA, you fly within 10nm of a significant number of airstrips and it seems a bit over the top to be continuously broadcasting your transit if you up at 7, 8 or 9 thousand feet.

Thanks Bob. The good airmanship/common sense approach certainly works for me - just wanted to know if I had missed a magic number buried somewhere obscure deep inside the documentation.

For others following this, I have found a reference in the AIP to the old 5,000' rule. Have a read of ENR 1.4 para 3.3.

Good one Ray. I must admit I had missed that reference myself. It would make a good practice exam question for Air Law. Thanks for that.

Some of you old folk may recall that once the boundaries of CTAFs were marked on VTC and ERC charts. That is not the case now because it was agreed that a CTAF is actually a frequency, not a particular piece of airspace.

It's interesting to note that at recent seminars, CASA has made a point of saying that a CTAF is not an area with boundaries, it is simply a frequency to be used by pilots who consider that they may be mixing it with local traffic. For example they say you cannot enter a CTAF because a CTAF has no defined boundaries. The reference to ten miles is an indication of the point at which you should begin monitoring the CTAF. That AIP reference does imply that a CTAF does have physical boundaries. I'll point that out to the people in the CASA pilot education section.

Bob

Thanks Bob, I will follow this discussion with interest. I had a chat with my instructor yesterday about when it is appropriate to monitor the CTAF frequency versus when a call should be made.

For example, if flying within 10nm but traversing outside say 5nm, I think a monitoring of 126.7 is sensible (no call), however if flying within 5nm of the aerodrome a call seems sensible unless above 5,000'. Above 5,000' AGL to my mind (AIP references above MSL) then monitoring would be acceptable (no call).

The alternative is to clog up the 126.7 frequency with needless calls that you can often hear over 100nm away from your position.