To be honest, This could not have happened the way they describe. Something else happened...
1. The rudder trim control knob requires several turns before you even get 1 degree of trim. (called a switch in the video)
2. There is no way the "yaw damper" could allow the aircraft to yaw far enough to fall into a dutch roll. Some Yaw dampers have been found defective but since have been replaced or modified per a fleet-wide service bulletin.
Yaw Damper - prevents the aircraft from moving in the "YAW" parameter. Drifting your car is movement in the yaw parameter.
Dutch Roll - When an aircraft moves in the yaw parameter to a point where the trailing wing air stream is blocked by the fuselage. That wing loses lift and drops. When an aircraft turns, it "slips" out of the air sideways. Once an aircraft has slipped (the dramatic loss of altitude in the video), the wing rarely can regain lift.
I don't know if that was a cover up or not but, I'm guessing one of the Nippon Air Execs is going to get a "Tokyo Neck-tie" soon
OK... now I have 2 questions....
1) why do they call it a Dutch Roll .... and not a French Baggett???
2) what's a Tokyo neck tie.... ....... .... ....