Pontius wrote:
What we do not know is the norm for handshakes.
Information Provided by AAIB (UK Air Accidents Investigation Branch):
If the ground station has not heard from an aircraft for a hour it (the ground station) will transmit a "logon /log off" message sometimes referred to as a ping, using the aircraft's unique identifier"
From the AAIB report there were satcom transmissions at 16:30, 16:40 and 16:55 (approximate UTC) that would be consistant with 'push back, wheels up, and FL100, the next satcom was at 1707 (cruise alt).
I was given to believe that ACARS transmissions were routed (automatically) to VHF, and failing that Satcom was used. If the AAIB data is correct, then it implies that Satcom transmits "something" when ACARS is transmitting via VHF. (otherwise there would be no doppler analysis of the first four transmissions).