flyingchanges asked, "And how is the acars still transmitting in a flat spin?"
I contend that as long as the plane was not on emergency power ACARS had the capability to transmit and reach the satellite unless it was really in the middle of a Biblical deluge.
If you are worried about antenna aiming draw an airplane, any old outline sketch will do. The antenna is a 6dB gain model relative to an antenna that radiates identically in all directions. A gentleman named Poynting observed that if you draw a sphere around a transmitter antenna you cannot get more power out of that sphere than you put into it. With that in mind you get gain by sacrificing portions of the sphere to enhance other portions. The first thing most antennas in practical installations sacrifice is "the other hemisphere". If they are to look up they lose down. If they are to look down they lose up. That gives a cool 100% power boost, 3dB. If they cut the angle down further, say from being a section of a sphere from 0 to 90 degrees from vertical and it becomes oh maybe 60 degrees from vertical to pure vertical the gain boosts another (very) roughly 3dB. If I require less than 1 to 2 dB of loss from peak performance I've been figuring on 40 degrees and the Atlantic satellite in use was 10 degrees to the East.
Thus if the plane's attitude was within 20 to 30 degrees of horizontal and it had power for ACARS then ACARS messages could be sent.
There is question of whether or not there really were. Although to my untutored eyes they seem to cut off almost mid-sentence, so to speak. There looks like there should have been more story to tell.
Rain has been mentioned for the short signal loss that happened. That might, also, have been the plane coming down to a level where there was enough air bite to execute a turn or other attitude changing maneuver to recover from uncontrolled flight. That might also explain the loss.
The ACARS signal does give us some data to estimate, only estimate, the condition of the plane through 0215 as being roughly horizontal and with power. After that it was controlled or uncontrolled flight without power, most likely. We don't know for sure. But, this limits the range of guesses for what might have happened.
JD-EE