In an embodiment, an aircraft includes an airframe and a first propulsion assembly coupled to the airframe. The first propulsion assembly includes a first rotor hub and a first plurality of rotor blades non-uniformly spaced about the first rotor hub and operable to rotate in a rotor plane with the first rotor hub. The aircraft also includes a second propulsion assembly coupled to the airframe. The second propulsion assembly includes a second rotor hub and a second plurality of rotor blades non-uniformly spaced about the second rotor hub and operable to rotate in a rotor plane with the second rotor hub.