Abstract: A vibration control system for a rotor hub provides vibration attenuation in an aircraft by reducing the magnitude of rotor induced vibratory. The system can include a force generating device attached to a rotor hub which rotates along with the rotor at the rotational speed of the rotor. Vibratory shear force is generated by rotating unbalanced weights each about an axis non-concentric with the rotor hub axis at high speed to create large centrifugal forces. The rotational speed of the weights can be a multiple of the rotor rotational speed to create shear forces for canceling rotor induced vibrations. The amplitude of the generated shear force is controlled by indexing the positions of the unbalanced weights relative to each other, while the phase of the shear force is adjusted by equally phasing each weight relative to the rotor.

Abstract: A laminated elastomeric journal bearing has an outer sleeve having an inner surface, at least a portion of each end of the inner surface being a concave surface of revolution, and an inner sleeve having an outer surface, at least a portion of each end of the outer surface being a convex surface of revolution. Alternating layers of elastomer and metal are located between the sleeves, with adjacent surfaces of the layers and the sleeves being adhered to each other.

Abstract: A laminated elastomeric journal bearing has an outer sleeve having an inner surface, at least a portion of each end of the inner surface being a concave surface of revolution, and an inner sleeve having an outer surface, at least a portion of each end of the outer surface being a convex surface of revolution. Alternating layers of elastomer and metal are located between the sleeves, with adjacent surfaces of the layers and the sleeves being adhered to each other.

Abstract: In some examples, an oscillatory pumping system comprises: one or more active piston, a fluid, and two motors. The one or more active piston is disposed in a channel fluidically coupling two fluid chambers. The passive piston has a frequency response operable to counteract a vibratory displacement. The fluid is disposed in the channel and the two fluid chambers. The two motors couple to the one or more active piston. The two motors are operable to selectively change the frequency response of the passive piston based on oscillating the one or more active piston.

Abstract: A method of providing an anti-torque force in a rotorcraft with an anti-torque system comprised of a primary ducted tail rotor system mechanically connected to an engine, and a secondary ducted tail rotor system electrically connected to an electric power supply. The method includes receiving an indication of a change in the operating condition of the anti-torque system based upon a change in a rotorcraft condition input, a feedback input associated with a primary ducted tail rotor system and/or a secondary ducted tail rotor system, and/or a pilot input; responsive to the indication of the change, determining, by a control system, an anti-torque control input including at least a secondary output command for controlling the secondary ducted tail rotor system; and transmitting the secondary output command to the secondary ducted tail rotor system to energize at least one ducted tail rotor assembly therein to provide the second anti-torque force.

Abstract: The present application provides a drive link for a constant-velocity joint of an aircraft rotor, the link connecting a drive hub attached to a driveshaft to a rotor yoke. The link comprises a leading bearing connected to the drive hub, a trailing bearing connected to the yoke, a central portion between the bearings, and a tension loop connecting the bearings. The tension loop is formed from a composite material and is formed as a continuous band. The tension loop transfers drive forces from the leading bearing to the trailing bearing for driving the yoke in rotation with the driveshaft.

Abstract: A method of selectively preventing flapping of a rotor hub includes providing a flapping lock proximate to a rotor hub and shaft assembly and moving the flapping lock from an unlocked position to a locked position, the flapping lock operable in the locked position to prevent at least some flapping movement of the rotor hub relative to the shaft, the flapping lock operable in the unlocked position to allow the at least some flapping movement of the rotor hub relative to the shaft.

Abstract: There is provided a rotorcraft, including a body, including a front portion and a tail portion; a main rotor system coupled to the front portion of the body, the main rotor system operable to provide a lifting force on the body; and an anti-torque system coupled to the tail portion of the body, the anti-torque system including a primary tail rotor system and a secondary tail rotor system; wherein the primary tail rotor system and the secondary tail rotor system are operable to provide a first anti-torque force and a second anti-torque force. In other aspects, there are methods of providing anti-torque force in a rotorcraft.

Abstract: A vibration control system for a rotor hub provides vibration attenuation in an aircraft by reducing the magnitude of rotor induced vibratory. The system can include a force generating device attached to a rotor hub which rotates along with the rotor at the rotational speed of the rotor. Vibratory shear force is generated by rotating unbalanced weights each about an axis non-concentric with the rotor hub axis at high speed to create large centrifugal forces. The rotational speed of the weights can be a multiple of the rotor rotational speed to create shear forces for canceling rotor induced vibrations. The amplitude of the generated shear force is controlled by indexing the positions of the unbalanced weights relative to each other, while the phase of the shear force is adjusted by equally phasing each weight relative to the rotor.

Abstract: A pusher rotorcraft is provided in one example embodiment and may include at least one engine in mechanical communication with a drop-down gearbox; a driveshaft in mechanical communication with the drop-down gearbox, a main rotor gearbox, and a tail system gearbox; a main rotor system in mechanical communication with the main rotor gearbox; an anti-torque system in mechanical communication with the tail system gearbox; and a pusher propeller system in mechanical communication with the tail system gearbox.

Abstract: In one embodiment, a tiltrotor aircraft may comprise a fuselage; a biplane wing coupled to the fuselage, wherein the biplane wing comprises an upper wing structure and a lower wing structure; a plurality of tiltrotors coupled to the biplane wing; and at least one engine to power the plurality of tiltrotors.

Abstract: A multirotor aircraft comprises at least three proprotors. Each proprotor has a plurality of rotor blades pivotably attached to a mast assembly. When a rotor blade pitch angle is changed for a proprotor, all rotor blades on the proprotor change to a same pitch angle. The proprotors are configured to spin freely when a power source is disengaged or fails. In various embodiments, one or more engines provides power to each proprotor, or at least one engine provides power to two or more proprotors. A rotor blade control system is configured to control a collective rotor blade pitch angle on each proprotor independently of the rotor blade pitch on the other proprotors. The rotor blade control system is configured to set a negative collective rotor blade pitch angle on an unpowered proprotor, such as in response to manual inputs by a pilot or in response to current engine conditions.

Abstract: A vibration control system for a rotor hub provides vibration attenuation in an aircraft by reducing the magnitude of rotor induced vibratory. The system can include a force generating device attached to a rotor hub which rotates along with the rotor at the rotational speed of the rotor. Vibratory shear force is generated by rotating unbalanced weights each about an axis non-concentric with the rotor hub axis at high speed to create large centrifugal forces. The rotational speed of the weights can be a multiple of the rotor rotational speed to create shear forces for canceling rotor induced vibrations. The amplitude of the generated shear force is controlled by indexing the positions of the unbalanced weights relative to each other, while the phase of the shear force is adjusted by equally phasing each weight relative to the rotor.

Abstract: In some examples, an oscillatory pumping system comprises: one or more active piston, a fluid, and two motors. The one or more active piston is disposed in a channel fluidically coupling two fluid chambers. The passive piston has a frequency response operable to counteract a vibratory displacement. The fluid is disposed in the channel and the two fluid chambers. The two motors couple to the one or more active piston. The two motors are operable to selectively change the frequency response of the passive piston based on oscillating the one or more active piston.

Abstract: 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.

Abstract: In one embodiment, a rotor hub comprises a yoke for attaching a plurality of rotor blades, a constant velocity joint to drive torque from a mast to the yoke and to enable the yoke to pivot, and a rotor control system configured to adjust an orientation of the plurality of rotor blades. Moreover, the rotor control system comprises: a swashplate, an adapter ring, a plurality of actuators controlled based on a flight control input, a plurality of lower pitch links configured to transfer motion between the swashplate and the adapter ring, a plurality of phase adjustment levers configured to adjust a control phase associated with motion transferred between the swashplate and the adapter ring, and a plurality of upper pitch links configured to adjust a pitch of the plurality of rotor blades, wherein there are more upper pitch links than lower pitch links.

Abstract: One example of a rotor assembly comprises: a rotor hub operable to rotate based on rotation of a mast; a first rotor blade pivotally attached to the rotor hub; a bracing member pivotally attached to the rotor hub at a first end and pivotally attached to the first rotor blade at a second end; and a linkage mechanism coupling the first rotor blade to a second rotor blade. The bracing member is operable to transfer a coning movement of the first rotor blade to a movement of the linkage mechanism and a corresponding coning movement of the second rotor blade.

Abstract: A rotorcraft comprises a fuselage, a tail boom, a rotor system, and a centrifugal blower system. The centrifugal blower system comprises a centrifugal blower configured to generate thrust using an airflow, wherein the centrifugal blower is located within the tail boom. The centrifugal blower system also comprises a plurality of ducts configured to control the thrust generated by the centrifugal blower, wherein the plurality of ducts is located on a portion of the tail boom surrounding the centrifugal blower, and wherein the plurality of ducts comprises one or more adjustable ducts configured to vary a size of an associated duct opening.

Abstract: In one embodiment, a method may comprise coupling a plurality of reinforcement fibers to a plurality of spherical components; inserting the plurality of spherical components into an enclosure; and heating the enclosure to cause the plurality of spherical components to expand, wherein the plurality of spherical components expands to form a geodesic structure, wherein the geodesic structure comprises a plurality of polyhedron components configured in a geodesic arrangement.

Abstract: In one embodiment, a rotor hub comprises a yoke for attaching a plurality of rotor blades, a constant velocity joint to drive torque from a mast to the yoke and to enable the yoke to pivot, and a rotor control system configured to adjust an orientation of the plurality of rotor blades. Moreover, the rotor control system comprises: a swashplate, a phase adapter fulcrum, a plurality of actuators controlled based on a flight control input, a plurality of lower pitch links configured to transfer motion between the plurality of actuators and the swashplate, a plurality of phase adjustment levers configured to adjust a control phase associated with motion transferred between the plurality of actuators and the plurality of lower pitch links, and a plurality of upper pitch links configured to adjust a pitch of the plurality of rotor blades, wherein there are more upper pitch links than lower pitch links.