A rotary wing aircraft including a prime mover, a main rotor assembly having a first plurality of rotor blades operatively coupled to a main rotor shaft rotatable at a first speed ratio, a tail rotor assembly including a second plurality of rotor blades operatively coupled to a tail rotor shaft rotatable at a second speed ratio, and a variable ratio gearbox assembly mechanically connected to the tail rotor assembly. The variable ratio gearbox assembly operates to selectively vary the second speed ratio relative to the first speed ratio.