PPRuNe Radar
Having been flying for the last 33 years in private, military and professional civilian roles I am only too aware of the "depths of semantics in our industry". As a professional pilot I read the rule books and, in this case, I find the rules quite clear.
ICAO Annex 10 Volume V Para 4.1.3.2.1 states that:
"123.45 Mhz shall be designated for use as an Air-to-Air communications channel to enable aircraft engaged in flights over remote and oceanic areas, out of range of VHF ground stations......"
UK AIC 16/2003 makes it quite clear that this has been adopted by the UK CAA and that it applies to the UK FIR. Therefore, 123.45 MHz shall/should NOT be used as an
Air-to-Air channel within radio range of the UK FIR.
If you re-read my posts you will see that I did not say that it was:
.....'mandatory' for it not to be used anywhere else in VHF ground station coverage areas.
You are right that the appropriate CAA may also allocate 123.45 MHz for other uses within their FIR but, in all of instances that I can find, they are allocated as
Ground-to-Air channels. That is why AIC 16/2003 was issued in order to protect these channels.
"Within the UK and Europe there are a number of VHF ground stations operating air traffic and operational control services on 123.45 MHz. There have been numerous reports of aircraft within the UK FIR using this frequency as an unauthorised Air-to-Air open communications channel. Attention is brought to the fact that the resulting interference from unauthorised use of this channel is potentially detrimental to flight safety."