An elastic flapping hinge for connecting a rotor blade to a rotor hub of a rotary wing aircraft, comprising an elastic flapping hinge member arrangement that includes a hub attachment area for attachment to the rotor hub, a connection area for attachment to the rotor blade, and an elastic flapping hinge area that is arranged between the hub attachment area and the connection area and adapted to allow flapping movements, the elastic flapping hinge member arrangement comprising at least two elastic flapping hinge members having a first bending stiffness for flapping movements and a second bending stiffness for lead-lag movements, the first bending stiffness being smaller than the second bending stiffness, wherein the at least two elastic flapping hinge members diverge from each other in the elastic flapping hinge area by a predetermined divergence angle.

An elastic flapping hinge for connecting a rotor blade to a rotor hub of a rotary wing aircraft, comprising an elastic flapping hinge member arrangement that includes a hub attachment area for attachment to the rotor hub, a connection area for attachment to the rotor blade, and an elastic flapping hinge area that is arranged between the hub attachment area and the connection area and adapted to allow flapping movements, the elastic flapping hinge member arrangement comprising at least two elastic flapping hinge members having a first bending stiffness for flapping movements and a second bending stiffness for lead-lag movements, the first bending stiffness being smaller than the second bending stiffness, wherein the at least two elastic flapping hinge members diverge from each other in the elastic flapping hinge area by a predetermined divergence angle.

A rotor system includes a hub assembly, a first, second, and third rotor blade rotatably attached to the hub assembly, a first, second, and third damper pivotally attached to the hub assembly and pivotally attached to the first, second, and third rotor blade, respectively, and a control system operably associated with the first, second, and third damper. A method to control vibratory forces exerted on the hub assembly via the first and second rotor blade includes separately controlling a dynamic spring rate of each of the first and second dampers with the control system.

A rotor system includes a hub assembly, a first, second, and third rotor blade rotatably attached to the hub assembly, a first, second, and third damper pivotally attached to the hub assembly and pivotally attached to the first, second, and third rotor blade, respectively, and a control system operably associated with the first, second, and third damper. A method to control vibratory forces exerted on the hub assembly via the first and second rotor blade includes separately controlling a dynamic spring rate of each of the first and second dampers with the control system.

The present embodiments disclose a torque dependent and resonant operating thrust-generating rotor assembly including a cyclic pitch control system for controlling tilting moments about a longitudinal rotor blade axis of one or more rotor blades, in order to control the pitch angle of the rotor blades and thereby also the horizontal movements of a helicopter vehicle or a rotary wing aircraft. A rotor torque assembly of the rotor assembly is further configured to operate in resonance, thereby providing a resonant gain effecting a rotational offset in relation to changes in torque generated by the motor.

Embodiments disclosed herein present a spring system for use in a torque dependent rotor assembly designed to operate in resonance, where changes in applied torque controls the blade pitch angle and ultimately the movements of a rotary wing aircraft. More specifically, the present invention relates to a spring system used in such a rotor assembly where the stiffness of an associated spring member is allowed to vary in response to the torque applied from a motor to the assembly.

A proprotor system operable for use on a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode. The proprotor system includes a rotor hub and a plurality of proprotor blades coupled to the rotor hub such that each proprotor blade has three independent degrees of freedom relative to the rotor hub including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis. Each of a plurality of spherical bearings couples one of the proprotor blades with the rotor hub. In addition, each of a plurality of lead-lag dampers couples one of the proprotor blades with the rotor hub, wherein each lead-lag damper is aligned with the pitch change axis of the respective proprotor blade, thereby providing pitch independent lead-lag damping.

A rotor system includes a hub assembly, a first, second, and third rotor blade rotatably attached to the hub assembly, a first, second, and third damper pivotally attached to the hub assembly and pivotally attached to the first, second, and third rotor blade, respectively, and a control system operably associated with the first, second, and third damper. A method to control vibratory forces exerted on the hub assembly via the first and second rotor blade includes separately controlling a dynamic spring rate of each of the first and second dampers with the control system.

A rotor system includes a hub assembly, a first, second, and third rotor blade rotatably attached to the hub assembly, a first, second, and third damper pivotally attached to the hub assembly and pivotally attached to the first, second, and third rotor blade, respectively, and a control system operably associated with the first, second, and third damper. A method to control vibratory forces exerted on the hub assembly via the first and second rotor blade includes separately controlling a dynamic spring rate of each of the first and second dampers with the control system.

A system can include a flight controller for an aircraft that includes an electric motor that drives blades with a variable pitch, where the flight controller receives a command to change a flight characteristic of the aircraft and creates a torque command and a revolutions per minute (RPM) command. The system can also include a propulsion assembly, where the propulsion assembly creates a current command based at least in part on the torque command and the RPM command, creates a blade pitch command based at least in part on the torque command and the RPM command, communicates the current command to the electric motor to change a mechanical output of the electric motor, and communicates the blade pitch command to blade actuators to control the pitch of the blades. The current command and the blade pitch command cause the blades of the aircraft to rotate at a predetermined RPM.