Abstract: An anti-phase rotor system for an aircraft may include at least one rotor with at least two rotor blades. The aerodynamic profile of these two blades may be selected to create counteracting blade vortices to break up harmonic reinforcement due to the rotor blade passage. The aerodynamic profile may create a non-planar motion of one or more rotor blade passages, whereby the individual rotor blades are not co-planar during the rotation of said rotor. The rotor system may include a duct, which may include stationary vanes or struts configured in a manner so as to break up harmonic excitation to the rotor. The interior area of the duct at the area of the blade rotation may be designed in a manner so as to create a destructive rotor blade tip vortex interference.