121.5 is called "Guard" because it is the frequency that we all Guard............i.e. we listen out on the frequency for any urgent or distress calls.
The reason why pilots call other pilots "on guard" is because if we hear our callsign and the words "on guard" we know that whoever is calling us is on the radio tuned to 121.5 and not the other two we may be listening to at the same time.
The UK is the only country that I am aware of using 121.50 for non-emergency traffic.
Few if any aerodromes within the UK monitor 121.50. Thus coverage on 121.5 can be severly limited in certain areas despite an ATC unit being close at hand (Carlisle and the Lake District being an example).
Outside the UK as far as I am aware most Aerodrome ATC units listen out on 121.50 at all times.
To make matters worse, I have come across instructors sending off solo students with the message - if you get lost call 121.50 and ask for a training fix.
Perhaps the pilots could stop using 121.50 and start using 999 on their telephones just for the practice. What would the response be then?
What the UK CAA should considder is not simply the efect on crews monitoring 121.50 but just as importantly - adjacent FIRs............it can only be a matter of time before some practice eh er eh er on 121.50 over the Southern UK interferes with a genuine emergency over Northern France.
An aircraft at 3000ft over the South UK coast making a practice call on 121.50 can interfere with an emergency flightalso at 3000ft on 121.50 who is almost 100nm away (Near Paris) or a flight at FL350 some 250nm away (well South of Paris). Thus simply having the UK D+D say continue practice pan ( because they can't hear anything) is simply not good enough.......before permitting such a practice, the London D+D should be required to contact all adjacent FIR/ACCs and get permission to block their 121.50 with non-essential transmissions. I can guarantee that if they ask they will be told no because safety dictates that 121.5 is kept as clear as possible!
If the CAA is going to permit this practice then I believe that they are required to ensure that such use of 121.50 does not extend beyond the FIR boundary and since aircraft can make such calls up to FL244 then the posibility of interfeering with adjacent FIRs use of 121.50 needs serious consideration for safety sake.
Regards,
DFC