Fast response rotor system

A rotor system for a vertical take-off and landing (VTOL) aircraft, comprising:

• a hub configured to be rotated by an electric motor housed within the hub, the hub comprising a rotatable shaft defining a vertical axis of rotation;
• at least one rotor blade, each rotor blade having a root end and a chord extending from a leading edge to a trailing edge, the chord defining a chord length;
• a pitch-lag hinge assembly mechanically coupled between the root end of the rotor blade and the shaft of the hub, the hinge assembly comprising:
• a center portion rigidly connected to the shaft of the hub to rotate therewith;
• an arm having a proximal end fixed to the center portion and a distal end extending radially outward from the vertical axis of rotation, the arm defining an outboard distance from the hub to the blade;
• a first set of flanges rigidly affixed to the distal end of said arm;
• a blade coupler mechanically affixed to the root end of said rotor blade at a chordwise hinge location between 0.25 and 0.4 of the chord length, measured from the leading edge of the rotor blade;
• a second set of flanges rigidly affixed to the blade coupler, said second set of flanges interdigitated with said first set of flanges;
• and
• a hinge pin extending through said interdigitated first and second sets of flanges to define a pivot axis of the hinge, wherein the pivot axis is inclined relative to the vertical axis of rotation by a hinge angle in the range of 0 to 75 degrees;
• wherein said hinge pin permits rotation of the rotor blade about the pivot axis such that lagwise deflection of the rotor blade during operation induces a passive change in blade pitch, the amount of pitch change being proportional to the hinge angle and the lag angle of the rotor blade;
• wherein said arrangement of the hinge assembly provides coupling between pitch and lag motions, such that increased lag due to aerodynamic drag or dynamic loading results in an automatic increase in blade pitch, thereby enhancing thrust generation and reducing the time required to reach maximum thrust in response to changes in motor input;
• and wherein said length of the arm affects the stiffness of the lag response, with a longer arm increasing resistance to lag-induced motion about the hinge axis.