Regarding duplex bearing side nut.
Originally Posted by
ShyTorque
the control shaft would have also tended to rotate in the same direction as the hub, i.e. anti-clockwise. Any drag on the nut on that end would tend to tighten it because it has a right hand thread
Yes - as long as God was flying alongside holding the nut:-)
Thing is that the nut is not held by anything. Instead the shaft is prevented from rotating because it is clamped to the feedback arm on the far side. If the inner race began to turn on the shaft because of forces transmitted through the failing bearing the inner race would rotate anti-clockwise relative to the shaft. This might tend to UN-screw the nut on the shaft.
Since the split pin on that nut remained intact the nut was not rotated very much if at all. The AAIB say that the release torque on the nut was higher than expected - however no cause or explanation for this is actually stated. Tightening was not caused by the nut being rotated by forces transmitted through the failed duplex bearing.
Two earlier posts mentioned this aspect of the geometry also, I apologise that I have not credited them but at present I don't want to take the time to look for the posts.