Originally Posted by
Check Airman
Why’s that? If you can control all the radios from your panel, why reach across the cockpit?
Typically because in the event of an interruption in the process, like making or receiving a radio call, the switcher forgets to return tuning to the appropriate side. Now the offside tuning light remains illuminated, and no-one knows (immediately) why.
Conversely the offside tuning technique might be used if the the PF (helpfully?) tunes a new frequency while the PM uses the transmit switch on their side Audio Control Panel...