An aircraft rotor assembly has a central hub and a plurality of rotor blades coupled to the hub for rotation with the hub about an axis, each blade having a Lock number of approximately 5 or greater. A lead-lag pivot for each blade is formed by a flexure coupling the associated blade to the hub. Each pivot is a radial distance from the axis and allows for in-plane lead-lag motion of the associated blade relative to the hub, each pivot allowing for in-plane motion from a neutral position of at least 1 degree in each of the lead and lag directions. Elastic deformation of the flexure produces a biasing force for biasing the associated blade toward the neutral position, and the biasing force is selected to achieve a first in-plane frequency of greater than 1/rev for each blade.

A hinge assembly such as a lead-lag hinge can include a hinge pin assembly. The hinge pin assembly can include an outer cylinder, a shear pin that extends through the outer cylinder and having a first threaded end and a second threaded end, a first nut threaded on the first threaded end and a second nut threaded on the second end. An opposing force between the first nut and the second nut applies a compressive stress to the outer cylinder that may increase a resistance of the hinge pin assembly to wear and damage. In the case of complete failure of the outer cylinder, the shear pin can maintain structural integrity of the hinge pin assembly and of the hinge assembly.

A hinge assembly such as a lead-lag hinge can include a hinge pin assembly. The hinge pin assembly can include an outer cylinder, a shear pin that extends through the outer cylinder and having a first threaded end and a second threaded end, a first nut threaded on the first threaded end and a second nut threaded on the second end. An opposing force between the first nut and the second nut applies a compressive stress to the outer cylinder that may increase a resistance of the hinge pin assembly to wear and damage. In the case of complete failure of the outer cylinder, the shear pin can maintain structural integrity of the hinge pin assembly and of the hinge assembly.

A rotor system for a rotorcraft includes a rotor hub having a plurality of blade grips coupled thereto. Each blade grip has a rotor blade coupled thereto. A fairing is disposed at least partially around the rotor hub. Each of a plurality of lead-lag dampers is coupled to at least a respective one of the blade grips. Each lead-lag damper has a damper heat exchanger and a fluid pump operably associated therewith. A fairing heat exchanger is in fluid communication with the damper heat exchangers and the fluid pumps. Each lead-lag damper is configured to drive the respective fluid pump responsive to damping operations to pump a cooling fluid from the respective damper heat exchanger to the fairing heat exchanger.

A rotor system for a rotorcraft includes a rotor hub having a plurality of blade grips coupled thereto. Each blade grip has a rotor blade coupled thereto. A fairing is disposed at least partially around the rotor hub. Each of a plurality of lead-lag dampers is coupled to at least a respective one of the blade grips. Each lead-lag damper has a damper heat exchanger and a fluid pump operably associated therewith. A fairing heat exchanger is in fluid communication with the damper heat exchangers and the fluid pumps. Each lead-lag damper is configured to drive the respective fluid pump responsive to damping operations to pump a cooling fluid from the respective damper heat exchanger to the fairing heat exchanger.

One embodiment is a rotor system including a rotor hub comprising a plurality of extension arms for connecting rotor blades to the rotor hub; a plurality of dampers connected between a respective one of the extension arms and the rotor hub; and a fairing disposed over the rotor hub, the fairing including an inlet plenum through which air is drawn from outside the fairing into the fairing; and at least one duct for conducting the air toward the at least one of the dampers.

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.

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.

One embodiment is a rotor system including a rotor hub comprising a plurality of extension arms for connecting rotor blades to the rotor hub; a plurality of dampers connected between a respective one of the extension arms and the rotor hub; and a fairing disposed over the rotor hub, the fairing including an inlet plenum through which air is drawn from outside the fairing into the fairing; and at least one duct for conducting the air toward the at least one of the dampers.

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.