Abstract: The present invention provides an unmanned aerial vehicle (UAV) such as a rotorcraft and a method of improving the performance thereof. The UAV is equipped with an inflated bag to prevent or alleviate property damage and personal injury caused by a collision between the UAV and a foreign object (e.g. a human being and a pet). The inflated bag in the proximity of a propeller's tip can also disrupt the tip vortex of the propeller generated in UAV operation state. The invention exhibits numerous technical merits such as enhanced operational safety, UAV drag reduction, higher propulsive efficiency, and reduction of UAV vibration level, among others.