A good example of an engineering failure. There sure seems to be a problem when it comes to designing "jack" screws for aircraft control surfaces. That is and has been an accident waiting to happen.
Why is it so many parts on aircraft are redundant, yet the most important system there is on a plane is totally neglected as far as redundancy goes. In any aircraft that has a control cable system, (I suppose even the fancy flyby wire may even use some in some area? )redundancy is ignored at least in the ones I am familiar with. If a cable snaps, or a pulley pops, there goes that function, if its for the elevator maybe you will be lucky and can use trim to maintain some control. In the case of this plane and that Alaska plane years ago it is an out of control horizontal stabilizer that should have stops, and not be allowed to go so far that elevator can not still maintain flight. What were they thinking? Maybe all aircraft should be like the cirrus and have a parachute.