Nothing wrong with the Stab?
So they did 240kts at ca 6000feet.
ATC lost radio and Radar contact.
So problems with Electrics and or Electronics.
Maybe due to turbulence and cargo shift, maybe not?
But as it have been showed in quite a few accidents it only takes a few seconds with the wrong elevator inputs and it is all over.
FlyDubai is case in point, and that Russian 737.300 was the same.
But the Bombardier RJ in Sweden as described in an earlier post was the worst.
Lets for argument sake say they lost a generator or a bus, so that the aircraft was dumped in the hands of PF without any warning!
All it takes is a few seconds of zero or negative G and it becomes critical, THEN depending if they have all displays , You have to be quick and correct in the recovery.
This would also explain why the Transponder stopped working.
There was nothing wrong with the Stabilizer, is my wild guess, mainly because no Boeing to date has had this problem.
Minor OR major problem in Display, AP, Electronics and Electrics, with a small or big human factor problem I am afraid is most likely.
Regardless , a gruesome way to end.
As terrible as this is for friends and family, It could be worse.
It could be a regular passenger flight.
So lets learn.
Peace
Cpt B