Dry lubricated linear actuator for in blade rotor control

A rotary-winged aircraft comprising:

• an airframe;
• and
• a main rotor assembly operably connected to the airframe including 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 including:
• a rotor blade;
• a rotatable flap portion disposed along a span of the rotor blade;
• and
• a linear actuator disposed inside the rotor blade operably connected to the flap portion to rotate the flap portion about a flap axis, the linear actuator is absent from oil, grease or other fluid lubricant, the linear actuator including:
• a brushless DC motor;
• a screw shaft operably connected to the motor;
• an output piston operably connected to the screw shaft via a roller nut to transform rotary motion of the screw shaft into linear motion on the output piston;
• and
• a plurality of rolling elements disposed between the screw shaft and the roller nut;
• wherein one or more of the plurality of rolling elements, the roller nut and the screw shaft are dry lubricant coated.

An actuation system for a flap portion of a rotor blade comprising a linear actuator disposed at the rotor blade and operably connected to the flap portion to rotate the flap portion about a flap axis, the linear actuator absent from grease or oil for lubrication, the linear actuator including:

• a brushless DC motor;
• a screw shaft operably connected to the motor;
• an output piston operably connected to the screw shaft via a roller nut to transform rotary motion of the screw shaft into linear motion on the output piston;
• and
• a plurality of rolling elements disposed between the screw shaft and the roller nut;
• wherein one or more of the plurality of rolling elements, the roller nut and the screw shaft are dry lubricant coated.