From a 14 October 2004 (ie about three months ago not 12 months):
I spoke with my mate Swifty at AusSAR and he told me that ATS do not routinely monitor 121.5 MHz, some towers do have the capability using a handheld transceiver, and most aircraft B737 size above monitor the frequency in the cruise. AusSAR relies on Airservices and its ground air communications network to alert it when an emergency situation exists.
Just had a look a ICAO Annex 10, Vol V and it indicates 121.5 MHz is the aviation emergency channel and shall only be used 'for genuine emergency purposes' including its use as an operating frequency for distress beacons (that is ELTs, EPIRBs and PLBs).
The document goes on to say at 4.1.3.1.2 that 'the frequency 121.5 MHz shall be provided at:
a) all area control centres and flight information centres;
b) aerodrome control towers and approach control offices serving international aerodromes and international alternate aerodromes; and
c) any additional location designated by the appropriate ATS authority, where the provision of that frequency is considered necessary to ensure immediate reception of distress calls or to service the purposes specified [earlier].'
and, stating the bleeding obvious:
(4.1.3.1.4) 'The emergency channel shall be guarded continuously during the hours of service of the units at which it is installed.'
Swifty also told me that transmissions on 121.5 MHz can upset units homing to a radiating distress beacon so the frequency should only be used in an emergency. He also said that 406 MHz distress beacons also transmit a low powered 121.5 MHz signal for units to home to the distress beacon (the satellite won't be listening to this frequency from early 2009). But note, 121.5 MHz will remain the aviation distress frequency.
In short, only use 121.5 MHz for emergency situations, note that Airservices does not routinely monitor it (why?) except at some manned towers but not necessarily continuously, and many larger RPTs monitor the frequency in the cruise. So its usefulness in some areas when experiencing an emergency may be questionable and the frequency in use, the overlying ATS frequency if operating in G or the multicom frequency may be better options in these cases.
Thanks for the help Swifty.
Swifty in his drink told me that AusSAR is very much indebted to the high flyers (and for a rotor head that is difficult to swallow) that monitor 121.5 MHz and report distress beacon signals to Airservices to pass on to AusSAR . Unfortunately, the low end of town that are the major customers of the SAR services don't seem to give a toss for their fellow aviators. But then again, no one appreciates these things until it is their loved one out there.
I guess the bottom line is keep off 121.5 MHz unless it is related to an emergency situation. Chat somewhere else and the numbers or company are the best options. However, monitor 121.5 MHz if you have the radio capacity and advise Airservices or AusSAR directly via satphone (if you have the gear) if you hear a distress beacon or an emergency phase being declared by an aircraft.
By the way, Swify told me if it is furphie that the satellites picks up every transmission on 121.5 MHz as they are looking for a swept tone. I told him that my wife is too busy with the broom in the kitchen to be transmitting on VHF at the same time.
