A method and system which isolates two-per-rev hub spring moment vibrations while providing control power during zero-g flight in a two- bladed teetering rotor helicopter. Hub spring structure is connected between the rotor and the pylon to resist rotor flapping about the teeter axis and thus provide control during zero-g flight. To isolate from the fusilage the hub spring moment two-per-rev vibrations, the rotor is coupled to the pylon below the rotor center of gravity at a distance related to both the hub spring rates and the in-plane frequency of the helicopter blades.
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