Re: I would expect a longer process for re-certification
3. Why is there a stabiliser setting which can cause unavoidable aircraft loss anyway?
This was answered further up the page.
Trim adjusts the angle of the whole horizontal stabiliser (the "small wings" at the back of the plane). That's the most efficient way to do it - have the whole surface doing the same thing. Some other designs have a fixed section and a large movable section - which means that you are likely to have two surfaces not doing exactly the same thing.
The elevator that is worked by moving the control column is much smaller - provided the plane is trimmed correctly, only small amounts of force are needed to manoeuvre the plane. So the elevator can only over-ride the trim up to a certain point - after that, the effect from trimming is more than the elevator can counter. Hence the description above of having to realise what's going on, disable the trimming system, and then frantically wind the manual trim control far enough for the elevator to be able to get the nose up again. And while you are frantically doing this, with your co-pilot doing a gym weightlifting workout* holding the control column fully back, the plane is entering an ever steeping dive due to the excessive trim.
Don't forget, this isn't a case of "it trims the aircraft to a certain attitude" (ie constant nose down) - it trims the aircraft to a "rate of change of attitude" (ie increasing nose down).
* OK, perhaps slight exaggeration since the flight controls will still be power assisted or even fly by wire. But I bet that guy is pulling that column mighty hard against the stops !
Biting the hand that feeds IT
