The AVX coaxial main rotor/dual ducted fan configuration achieves a higher speed than conventional helicopters (coax, single rotor, or tandem) by virtue of auxiliary propulsion (the ducted fans), maintaining a level fuselage attitude, and low drag airframe design. The ducted fans provide all of the propulsive force to overcome parasite drag; the rotor only provides lift in cruise.
In conventional helicopters the rotor is “tilted” to provide the propulsive force. The rotor incurs an increase in profile power and induced power when it provides the propulsive force, which makes it less efficient than the ducted fans as a source of propulsive force. When the rotor is tilted to provide the propulsive force the fuselage pitches nose down which increases fuselage parasite and trim drag and aerodynamic download that requires an increase in rotor thrust; these effects increase power required.
The AVX coaxial rotor/dual ducted fan configuration is based on minimizing the parasite drag of the airframe and the rotor hubs and controls. These design features result in a cruise speed higher than conventional helicopters.