The present disclosure is directed to a detachable connection between a pitch control unit arm and a pitch horn of a blade holder in a tail rotor head of a tail rotor of a rotary wing aircraft. The detachable connection includes a pin connecting the pitch horn, attached to a blade holder, with the pitch control unit arm of a pitch control unit, by protruding through an arm through hole and at another edge through a pitch horn through hole. By this arrangement, material wear is reduced and maintenance intervals can be reduced. This is reached because the pin is designed as a sliding pin projecting between pitch horn and pitch control unit arm, which is running in the course of its length through a spherical bearing in form of a ball with a central ball through hole.

The present disclosure is directed to a detachable connection between a pitch control unit arm and a pitch horn of a blade holder in a tail rotor head of a tail rotor of a rotary wing aircraft. The detachable connection includes a pin connecting the pitch horn, attached to a blade holder, with the pitch control unit arm of a pitch control unit, by protruding through an arm through hole and at another edge through a pitch horn through hole. By this arrangement, material wear is reduced and maintenance intervals can be reduced. This is reached because the pin is designed as a sliding pin projecting between pitch horn and pitch control unit arm, which is running in the course of its length through a spherical bearing in form of a ball with a central ball through hole.

A gear box includes a housing, an actuator coupled to the housing, and a bearing assembly pivotably coupled to the actuator. The bearing assembly including an outer raceway, a cylindrical housing positioned within the outer raceway, and an annular bearing positioned between the outer raceway and the housing. The cylindrical housing has a first end and a second end opposite the first end. A sensor is coupled to the first end of the cylindrical housing and configured to monitor an operating condition of the annular bearing. A linkage couples the actuator to the second end of the cylindrical housing and an output shaft is rotatably coupled to the bearing assembly.

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 coaxial, dual rotor system includes a first rotor assembly positioned at a rotor axis. A first rotor quill shaft is operably connected to the first rotor assembly at the rotor axis to drive rotation of the first rotor assembly about the rotor axis. A nonrotating static mast extends along the rotor axis through the first rotor quill shaft. A second rotor assembly is positioned at the rotor axis. A second rotor quill shaft is operably connected to the second rotor assembly to drive rotation of the second rotor assembly about the rotor axis. The second rotor quill shaft is coaxial with the first rotor quill shaft and disposed inside of the static mast. A second rotor bearing is positioned between the second rotor assembly and the static mast to transfer loads from the second rotor assembly to the static mast.

A coaxial, dual rotor system includes a first rotor assembly positioned at a rotor axis. A first rotor quill shaft is operably connected to the first rotor assembly at the rotor axis to drive rotation of the first rotor assembly about the rotor axis. A nonrotating static mast extends along the rotor axis through the first rotor quill shaft. A second rotor assembly is positioned at the rotor axis. A second rotor quill shaft is operably connected to the second rotor assembly to drive rotation of the second rotor assembly about the rotor axis. The second rotor quill shaft is coaxial with the first rotor quill shaft and disposed inside of the static mast. A second rotor bearing is positioned between the second rotor assembly and the static mast to transfer loads from the second rotor assembly to the static mast.

An aircraft rotor system includes a rotating pitch change shaft which rotates about an axis, a translating element disposed within the rotating pitch change shaft and movable along the axis and a pitch change bearing assembly which transfers movement of the translating element to the pitch change shaft. The pitch change bearing assembly includes a primary bearing and a secondary bearing coupled to the rotating pitch change shaft via the translating element when the primary bearing is in a first mode. A thrust shoulder is coupled to the translating element. The thrust shoulder is movable into engagement with the secondary bearing in response to failure of the primary bearing such that in a second mode, movement of the translating element is primarily transferred to the pitch change shaft via the secondary bearing.

An aircraft rotor system includes a rotating pitch change shaft which rotates about an axis, a translating element disposed within the rotating pitch change shaft and movable along the axis and a pitch change bearing assembly which transfers movement of the translating element to the pitch change shaft. The pitch change bearing assembly includes a primary bearing and a secondary bearing coupled to the rotating pitch change shaft via the translating element when the primary bearing is in a first mode. A thrust shoulder is coupled to the translating element. The thrust shoulder is movable into engagement with the secondary bearing in response to failure of the primary bearing such that in a second mode, movement of the translating element is primarily transferred to the pitch change shaft via the secondary bearing.

A helicopter autopilot system includes an inner loop for attitude hold for the flight of the helicopter including a given level of redundancy applied to the inner loop. An outer loop is configured for providing a navigation function with respect to the flight of the helicopter including a different level of redundancy than the inner loop. An actuator provides a braking force on a linkage that serves to stabilize the flight of the helicopter during a power failure. The actuator is electromechanical and receives electrical drive signals to provide automatic flight control of the helicopter without requiring a hydraulic assistance system in the helicopter. The autopilot can operate the helicopter in a failed mode of the hydraulic assistance system. A number of flight modes are described with associated sensor inputs including rate based and true attitude modes.