Originally Posted by
vilas
Half elevator will have to move double to produce dynamic load of both elevators. So they will keep hitting the extremities that can damage the elevator. So it's movement is restricted to less than full. That makes it less than half effective. This is known.
I do remember flying half-elevator very recently in my (somewhat study-level) A321 Home Sim. Certainly, the roll moments are very non trivial, leading to some pretty uncomfortable flying.
What did help a lot though, was the use of the THS, which worked on both sides of the elevators. (idk if it would work IRL).
As an engineering student, and studying how torsion loads work, it's actually pretty impressive how the fuselage is able to handle these forces so effectively, one eg. where I think it couldn't, was in the Lauda Air crash, where a portion of the right elevator broke off in the dive.