wiggy
The EICAS message/alert might be the way to go but a couple of observations:
1. Are you going to have the alert displayed every time you deliberately go off 121.5 to get ATIS or talk to company et.al...........
2. Will an alert be triggered, if, say, VHR X has 121.5 as the active freq, , the crew have correct audio selected on the ACP but volume(s) is/are turned down.
It wouldn't be up to just me obviously. We would have to agree on the best protocol.
1. Could do, or perhaps not until after say 1 minute of non monitoring 121.5, so the caution will not appear straight away when PM is talking to company or getting weather, but will pop up after a time period - to be determined?
2. There is no technical reason why not.
Perhaps an even easier way of doing this would be to monitor the audio output of box 1 downstream of the ACP selector and volume control and trigger an Amber ECAM caution or Memo "Check Comms" after a period of radio silence longer than say a few minutes. This would detect sleeping receivers, un-selected radios and radios turned right down.