Originally Posted by
JamesT73J
Something I need a bit of education about. I understand the 2/rpm bounce from aerodynamic loads on a 2-bladed rotor, There's some reference to the accident aircraft exhibiting tail wag at ground idle. I'm a little confused about the dynamics here; there's no aerodynamic load, is this just balance of a rotating mass? How would composite blades exacerbate this, compared to the OEM aluminium honeycomb blades?
First, the ACS pertains to an incident from Sept 2024 and is not associated with the NYC accident. However, both the “collective bounce” mentioned in the ACS and the “tail wag” occur with Bell blades as well. Bell issued an OSN in the 70s on the “collective bounce” and Post 225 offers reasons for the tail wag, which is more an excessive 1 per at mast pole/MR hub connection. In severe cases you can also see its effects with the landing gear crosstube flexing in rhythm with the tailboom wag. Now whether the VH blades provide an easier path to those 2 conditions I don’t any recall references to that, other than both VH and Bell provided the same guidance steps to mitigate those events.