VHA News
We have had onset of severe vertical vibration in 206L1 with Van Horn Blades when lightly loaded and low fuel.
Two separate machines and two different pilots. In both cases pilots described the vibration as severe enough to the point where they thought they had a major component failure. Van Horns statement
"The resulting vertical hop can become very uncomfortable" is very understated.
Both incidents reported to Van Horn and other operators have been experiencing same issues hence the release of the Van Horn statement.
In the first occurrence pilot naturally dropped collective which made the vibration worse. As Van Horn subsequently stated using cyclic to offload the disc and the frequency of Nodal Beam interaction resolves the issue.
It has reoccurred numerous time since on our aircraft in a similar configuration and operating environment (mountain, turbulent/rough air).
Below a news article of another operator a few days ago.
ASL