A system and process for countering the vibrations induced in an aircraft by the windmilling of an engine fan may produce a first electric flight control command for a servocontrol to use in actuating a control surface of the aircraft. The servocontrol is slaved to the first electric flight control command, and the servocontrol's operation is limited to a reduced frequency band. Vibrations induced by the windmilling of the engine fan are monitored, and, when the monitored vibrations exceed a threshold, a second electric flight control command for application to the servocontrol is computed to oppose the induced vibrations. Also, the first and second electric flight control commands are summed to produce an overall control command for the control surface, and the servocontrol is temporarily slaved to the overall control command for operation in a widened frequency band.