Lu,
Well the impression I was left with was far from favorable and there was defiantly an arrogance which was along the lines of, We are Robinson Helicopters, we know best, because we say so.
You are correct in your description of the damage to the main rotor head, the teeter bushing had worn to the point of failure in the same plane as head rotation.
Because the aircraft had been used in a high load condition I was expecting to see the wear in a vertical plane, but I except your explanation as to the reasons.
I'm an electrical engineer and mechanical stress isn't really my thing but I do remember the mechanical guys on various projects doing there absolute utmost to avoid cyclical torsional bending on shafts.
This begs the question, if cyclical torsional bending on the mast becomes excessive, can it lead to mast failure without mast bumping ever occurring?
If so how much?
Does flying out of trim increase this?
Jiff