A system and method for performing an external inspection on a rotor blade of a wind turbine are disclosed. The system may generally include a frame configured to extend at least partially around an outer perimeter of the rotor blade and a sensing device coupled to the frame. Additionally, first and second spacer arms may extend from the frame. The first spacer arm may be configured to contact a pressure side surface of the rotor blade. The second spacer arm may be configured to contact a suction side surface of the rotor blade.