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.

A method for equalizing rolling moments at high advance ratios is disclosed including impelling an aircraft in a forward direction at an airspeed by means of a thrust source and rotating a rotor of the aircraft at an angular velocity with respect to the airspeed effective to cause a positive total lift on each blade due to air flow over the blades in the retreating direction when the blade is moving in the retreating direction. The rotor includes an even number of blades placed at equal angular intervals around the rotor hub. One or both of cyclic pitch and rotor angle of attack are adjusted such that a rolling moment of the retreating blade due to reverse air flow is between 0.3 and 0.7 times a rolling moment on the advancing blade due to lift.

A method for equalizing rolling moments at high advance ratios is disclosed including impelling an aircraft in a forward direction at an airspeed by means of a thrust source and rotating a rotor of the aircraft at an angular velocity with respect to the airspeed effective to cause a positive total lift on each blade due to air flow over the blades in the retreating direction when the blade is moving in the retreating direction. The rotor includes an even number of blades placed at equal angular intervals around the rotor hub. One or both of cyclic pitch and rotor angle of attack are adjusted such that a rolling moment of the retreating blade due to reverse air flow is between 0.3 and 0.7 times a rolling moment on the advancing blade due to lift.

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.

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.

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.

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.

A pneumatic actuated trim tab system adapted to be mounted on a rotor blade to pneumatically alter aerodynamic properties of the rotor blade. The system includes an inflatable diaphragm adapted to be mounted on one or each side of the rotor blade; a deformable plate attached to each of the inflatable diaphragm, such that inflation and deflation of the inflatable diaphragm causes movement of each of the plates; a valving system connected to each inflatable diaphragm to allow input of a fluid into each inflatable diaphragm and allow release of a fluid out of each inflatable diaphragm; and a controller for controlling fluid pressure into and out of each inflatable diaphragm using the valving system.