A transmission structure of a helicopter according to one aspect is a transmission structure that transmits power from a prime mover to a rotary wing in the helicopter. The transmission structure includes: a housing; an input shaft that transmits the power of the prime mover to a gear arranged in the housing; a bearing supporting the input shaft in the housing such that the input shaft is rotatable, the bearing including an annular inner ring that holds the input shaft, an annular outer ring that is arranged outside the inner ring in a radial direction and fixed to the housing, and rolling elements sandwiched between the inner ring and the outer ring; and a sleeve that is sandwiched between an inner peripheral surface of the inner ring and the input shaft and is lower in heat conductivity than the inner ring and the input shaft.

A method for controlling a thermal and electrical power plant for setting in motion at least one rotary member of a rotorcraft, the power plant comprising at least one heat engine and an electrical system provided with at least one electric machine. The method comprises: selecting, with a selector, an operating mode chosen from several operating modes; determining a density altitude and comparing, with a controller, the current density altitude and a threshold density altitude; and controlling, with the controller, the at least one electric machine depending on at least the chosen operating mode as well as the comparison and a necessary power to be supplied to the power transmission system.

A method for controlling a thermal and electrical power plant for setting in motion at least one rotary member of a rotorcraft, the power plant comprising at least one heat engine and an electrical system provided with at least one electric machine. The method comprises: selecting, with a selector, an operating mode chosen from several operating modes; determining a density altitude and comparing, with a controller, the current density altitude and a threshold density altitude; and controlling, with the controller, the at least one electric machine depending on at least the chosen operating mode as well as the comparison and a necessary power to be supplied to the power transmission system.

A helicopter with a rotor pivotally connected to a shaft by a universal joint or ball and socket joint. The helicopter includes: a fuselage; a rotor mast that is fixed against relative rotation with respect to the fuselage; at least one blade; a motor for rotating the at least one blade; and a universal joint or ball and socket joint. The universal joint or ball and socket joint: (i) is disposed between the at least one blade and the rotor mast, with the at least one blade being rotatable relative to the universal joint or ball and socket joint; (ii) is disposed between the motor and the rotor mast; and (iii) is fixed against relative rotation with respect to the rotor mast, such that, pivoting of the universal joint or ball and socket joint causes the at least one blade and the motor to tilt.

A helicopter with a rotor pivotally connected to a shaft by a universal joint or ball and socket joint. The helicopter includes: a fuselage; a rotor mast that is fixed against relative rotation with respect to the fuselage; at least one blade; a motor for rotating the at least one blade; and a universal joint or ball and socket joint. The universal joint or ball and socket joint: (i) is disposed between the at least one blade and the rotor mast, with the at least one blade being rotatable relative to the universal joint or ball and socket joint; (ii) is disposed between the motor and the rotor mast; and (iii) is fixed against relative rotation with respect to the rotor mast, such that, pivoting of the universal joint or ball and socket joint causes the at least one blade and the motor to tilt.

A failsafe multimode clutch assembly positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly uses pressurized lubricating oil to shift the bypass assembly between the engaged position and a disengaged position. A lock assembly enables and disables actuation of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit enables a unidirectional torque transfer mode of the clutch assembly. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

A multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly shifts the bypass assembly between engaged and disengaged positions. An engagement status sensor is configured to determine the engagement status of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

A multimode clutch assembly is positioned in a powertrain of a rotorcraft. The clutch assembly includes a freewheeling unit having a driving mode in which torque applied to the input race is transferred to the output race and an overrunning mode in which torque applied to the output race is not transferred to the input race. A bypass assembly has an engaged position that couples the input and output races of the freewheeling unit. An actuator assembly shifts the bypass assembly between engaged and disengaged positions. An engagement status sensor is configured to determine the engagement status of the bypass assembly. In the disengaged position, the overrunning mode of the freewheeling unit is enabled such that the clutch assembly is configured for unidirectional torque transfer. In the engaged position, the overrunning mode of the freewheeling unit is disabled such that the clutch assembly is configured for bidirectional torque transfer.

A rotor for an aircraft is described, comprising an input shaft rotatable around a first axis; an output member rotatable around a second axis; a coupling element functionally interposed between the input shaft and the output member and adapted to transmit the motion from the input shaft to the output member; the coupling element is configured to allow, in use, a fixed or variable inclination between the respective first and second axes; the coupling element comprises at least a first corrugated element made of an elastically deformable material; the first corrugated element allows the inclination through elastic deformation.

A sensor for monitoring rotors includes a rotating shaft coupled to a set of rotor blades and a non-rotating tube at least partially disposed within the rotating shaft and coupled to the rotating shaft. The non-rotating tube includes a first end and a second end, a sensor mount disposed within the non-rotating tube proximate to the second end of the non-rotating tube. One or more sensors are attached to the sensor mount.