Re;
"it might be the only way that ATC can call you if you screw up a frequency change, or suffer an undetected radio failure."
Unless things have changed,
AsA do not have the 121.5 facility avbl for Controllers / Flight Watch staff to use...
The ONLY time I ever had the facility available was for a 'combined forces' military exercise in Derby - 'Pitch Black' or 'Kangaroo', or one of 'those' when the FSU had a portable 'Bayside' VHF loaned to us for use 'if required' to monitor the 'red' or 'blue' forces doing 'funny' night ops.....
And, it actually got used.....once.....to check that, following a 'spurious' call, that the acft in question was 'safe'.
Cheers
