* Imbalance of the main rotor head. Firstly, do not tighten rotor blade bolts to much. The blades must be able to align themselves by centrifugal force. Then check blade balancing and/or try a different set of rotor blades.<br /> | * Imbalance of the main rotor head. Firstly, do not tighten rotor blade bolts to much. The blades must be able to align themselves by centrifugal force. Then check blade balancing and/or try a different set of rotor blades.<br /> |