Rotor blade with integrated passive surface flap

A driven horizontal rotor of a rotary-wing airplane comprising a plurality of rotor blades, each of the rotor blades comprising:

• an elongated main body, the main body including:
• a leading edge,
• a trailing edge, and
• an upper surface extending between the leading edge and the trailing edge,
• at least one flap,
• having a front end and a rear end, and
• mounted to the main body at its front end swiveling about a swiveling axis running in parallel to the radial axis of the rotor blade,
• wherein the flap has a basic position in which it lies flat against the upper surface of the main body, wherein the flap is designed to be passively swiveled by aerodynamic forces and inertial forces about its swivel axis to raise above the upper surface of the main body, and wherein the flap is swivel mounted to the main body in such a way that a reset force acts upon the flap to reset it into its basic position.