A rotor blade assembly includes a rotor blade, a rotatable flap portion disposed along a span of the rotor blade. A rotary actuator is located inside the rotor blade and is operably connected to the flap portion to rotate the flap portion about a flap axis. A rotary-winged aircraft includes an airframe and a main rotor assembly operably connected to the airframe. The main rotor assembly includes a plurality of rotor blade assemblies rotatable about a rotor assembly axis. At least one rotor blade assembly of the plurality of rotor blade assemblies includes a rotor blade and a rotatable flap portion disposed along a span of the rotor blade. A rotary actuator located inside the rotor blade and is operably connected to the flap portion to rotate the flap portion about a flap axis. The rotary actuator is absent oil, grease or other fluid lubricant.