There was an FR post earlier today (which has since been pulled) in which an apparent FR aviation expert informed us that the ACARS sends data ONLY on significant events (gear-up, gear-down, achieving cruise) and NEVER on time. So the reports that it sent out data every half hour are wrong - it would not be expected to send out more data until gear-down (which didn’t happen).
Hello Izzy. You got that right. There was no indication that the ACARS was turned off. The last ACARS data downlink was at cruise initiation at 1:07. It’s next scheduled data downlink should have been at geardown. No geardown means no ACARS downlink. That is the way it is supposed to work.
Reportedly, they turned off ACARS first, before the transponder. What they neglected to do, however, was also to turn off the satellite radio system that ACARS uses. It pings the geosynchronous satellite from time to time, even if it has no traffic, and the satellite is able to gauge the airplane's distance, but not its direction, from the ping timing. That is what those circular arcs on the map are based upon.
“There was an FR post earlier today (which has since been pulled) in which an apparent FR aviation expert informed us that the ACARS sends data ONLY on significant events (gear-up, gear-down, achieving cruise) and NEVER on time. So the reports that it sent out data every half hour are wrong - it would not be expected to send out more data until gear-down (which didn’t happen).”
Actually he said that the ACARS sends reports every hour and that the engine monitoring system sends reports on gear-up, cruise and gear-down.