Originally Posted by
The Sultan
What you are describing is PIO (pilot induced oscillation) and it is not limited to two bladed helicopters. What I am alluding to is actual “slop” in the swashplate assembly due to worn components. If these are present the swashplate has a degree of freedom to pump the rotor independent of actual control position.
Except the issue with VH blades has been documented and discussed with being due to collective bounce and not swashplate play. And while I've seen a number of interesting results when the swashplate friction is not properly set on the 206 series, if the friction is at its required limits and you had enough play in it to affect blade track that sw/plate was well past its useful wear limits and would have been considered unairworthy. I doubt seriously this operator would have allowed that level of neglect.