US Patent 9551990 Unmanned aerial vehicle landing system

The present disclosure provides an unmanned flying vehicle (UAV) operable in a plurality of operating modes including a normal operations mode, a safe landing mode and an emergency landing mode. The normal operations mode is initiated when no errors are detected in the system. The safe landing mode is initiated when one or more non-critical components of the UAV are in non-responsive mode or do not work as desired. The emergency landing mode is initiated when one or more critical components are in non-responsive mode or do not work as desired. Further, the safe landing mode overrides the normal operations mode and the emergency landing mode overrides both the normal operations mode and the safe landing mode.