QUOTE: Free Flapping HS I don't want to get involved in this, but just thought I'd point out one thing if I might. If the HS is ever free to move about it's pivot point (ie sans jackscrew) it will align itself with the oncoming air (weathervaning), not slam to one or the other stop. It's takes the path of least resisitence.
END QUOTE
I think the writer of the above must bear in mind that the horizontal control surfaces consist (normally) of three parts;
a) the stabilizer which leading edge is moved by a jackscrew
b) the elevator which is operated from input by cockpit controls and
c) The trim tab which is used to trim the aircraft for hands off (auto pilot) flying. (or a combination of b) and c) where the trim tab does all the work to move the elevator)
Now visualise the jack disconnecting from the stabilizer. Would the airflow then not move the stabilizer either nose up or down depending on the starting position ? Yes, the elevator, if disconnected would free float and take a position in the flow influenced by the trim tab position.