An aircraft uses trajectory-based control algorithms for blade pitch (or twist). This approach greatly enhances the ability of the actuator to accurately achieve the desired blade pitch and to track the commanded pitch position. An actuator includes an electronic rotor blade controller that converts communicated or desired changes in pitch (or similar parameter) to actual physical effects that match the desired changes as closely as possible. The controller preferably includes a motor drive circuit, such as an h-bridge, a communication circuit for connection to external commands, and a processor with associated enabling circuitry (e.g. memory, I/O) to coordinate and implement the control.

A method for stabilizing a motion of a rotor blade of a rotor comprising the steps: read into a controller, a measurement from a sensor responsive to said rotor blade; determine an out-of-compliance motion of the rotor blade; and output a first control signal to an actuator affecting the rotor blade such that a vibration mode of said rotor blade is dampened. The damping may be achieved by changing the drag, lift or torsion of the rotor blade. The out-of-compliance motion may be a lead, lag, upward motion, downward motion or twist of the rotor blade away from a nominal value.

A rotor blade assembly connectable to a rotor hub configured to rotate about a center axis includes a torsional pitch member coupled to the rotor hub, a torque tube coupled to the torsional pitch member, wherein the torsional pitch member extends away from the center axis through a portion of the torque tube, a blade coupled to the torque tube, and a pitch control member coupled to the torque tube and configured to control a pitch angle of the blade, wherein the torsional pitch member includes a first curvilinear channel and a second curvilinear channel each having a front side and a back side, wherein the first curvilinear channel and the second curvilinear channel are disposed adjacent to each other, such that the back side of the first curvilinear channel faces the back side of the second curvilinear channel.

A rotor blade assembly connectable to a rotor hub configured to rotate about a center axis includes a torsional pitch member coupled to the rotor hub, a torque tube coupled to the torsional pitch member, wherein the torsional pitch member extends away from the center axis through a portion of the torque tube, a blade coupled to the torque tube, and a pitch control member coupled to the torque tube and configured to control a pitch angle of the blade, wherein the torsional pitch member includes a first curvilinear channel and a second curvilinear channel each having a front side and a back side, wherein the first curvilinear channel and the second curvilinear channel are disposed adjacent to each other, such that the back side of the first curvilinear channel faces the back side of the second curvilinear channel.

A system to prevent or limit resonance in a rotocraft. The system comprises an airframe, a rotor system having a natural frequency and including a rotor and a mast attached to the airframe, and a non-linear spring positioned between the rotor system and the airframe. The rotor system and the airframe are operable to move relative to each other as the rotor system begins to oscillate. The non-linear spring is configured to be deformed when the rotor system and the airframe move relative to each other such that the deformation of the non-linear spring causes the natural frequency of the rotor system to change. Also disclosed is a related method for preventing or limiting resonance in a rotorcraft.

A system to prevent or limit resonance in a rotocraft. The system comprises an airframe, a rotor system having a natural frequency and including a rotor and a mast attached to the airframe, and a non-linear spring positioned between the rotor system and the airframe. The rotor system and the airframe are operable to move relative to each other as the rotor system begins to oscillate. The non-linear spring is configured to be deformed when the rotor system and the airframe move relative to each other such that the deformation of the non-linear spring causes the natural frequency of the rotor system to change. Also disclosed is a related method for preventing or limiting resonance in a rotorcraft.

A main rotor trim tab retention system includes, a blade housing having flanges separated by a cavity defined between the flanges, and a trim tab assembly. The trim tab assembly includes, a trim tab having an aerodynamic surface, at least one arm extending from the trim tab positionable within the cavity while the trim tab extends outward from the cavity, and a spherical bearing connecting the trim tab and the at least one arm, the spherical bearing having a first axis which is substantially perpendicular to the aerodynamic surface of the trim tab. The at least one arm is pivotable about the spherical bearing about a second axis substantially perpendicular to the first axis to rotate the trim tab relative to the blade housing.

A main rotor trim tab retention system includes, a blade housing having flanges separated by a cavity defined between the flanges, and a trim tab assembly. The trim tab assembly includes, a trim tab having an aerodynamic surface, at least one arm extending from the trim tab positionable within the cavity while the trim tab extends outward from the cavity, and a spherical bearing connecting the trim tab and the at least one arm, the spherical bearing having a first axis which is substantially perpendicular to the aerodynamic surface of the trim tab. The at least one arm is pivotable about the spherical bearing about a second axis substantially perpendicular to the first axis to rotate the trim tab relative to the blade housing.

According to one aspect, a lubricant level sensing system for an actuator is provided. The lubricant level sensing system includes a pressure port in an outer housing of the actuator, a pressure sensor, and a pathway from the pressure port to the pressure sensor. The pathway establishes fluid communication between the pressure sensor and a free volume of an internal cavity of the outer housing relative to a lubricant level in the internal cavity such that the pressure sensor detects a pressure of the free volume used to derive the lubricant level.

According to one aspect, a lubricant level sensing system for an actuator is provided. The lubricant level sensing system includes a pressure port in an outer housing of the actuator, a pressure sensor, and a pathway from the pressure port to the pressure sensor. The pathway establishes fluid communication between the pressure sensor and a free volume of an internal cavity of the outer housing relative to a lubricant level in the internal cavity such that the pressure sensor detects a pressure of the free volume used to derive the lubricant level.