overthewing;
As a non pilot, I have no idea what COM3 is, but I was surprised the post elicited no interest at all.
VHF COM3 is not the main communications radio. It is used by ACARS and by the 3rd pilot when communicating with company. When out of VHF range, which AF447 was, ACARS automatically switches over to SATCOM. Just like the LAV ACARS message, there would be no real interest in the snag - it's a non-issue.