A coaxial rotor system for a rotorcraft includes a mast, a top rotor assembly and a bottom rotor assembly. The top rotor assembly is coupled to the distal end of the mast. The bottom rotor assembly includes a motor configured to provide rotational energy to the mast, thereby rotating the top rotor assembly. The bottom rotor assembly experiences a torque reaction force responsive to the motor rotating the mast such that the top and bottom rotor assemblies counter rotate.

A mechanical power transmission that pivots about an axis to vary an angle between an input shaft and an output shaft. The mechanical power transmission includes an input gear having an input shaft that couples to a drive shaft, an output gear having an output shaft that couples to a tail rotor, a first intermediate gear rotationally coupled to the input gear, and a second intermediate gear rotationally coupled to the output gear. The mechanical power transmission further comprises a shaft that mechanically couples the first intermediate gear with the second intermediate gear, where a centerline of the shaft is coincident with the axis.

The invention herein comprises a kit and method that may be used to replace damaged and worn stabilizer bearings in both the Echo and Delta Apache helicopter. The kit includes a removal assembly that includes a bolt coupled to a cutting means. Tightening of the bolt causes the cutting means to cut the damaged and worn bearing from its housing. A staking means is disclosed that allows the staking of a replacement bearing in the housing is provided. The staking assembly joins the replacement bearing to the housing so that it is tight. And, an installation assembly is disclosed that utilizes the bolt utilized in the cutting means coupled to a hex nut.

A rotary wing aircraft and a rotor assembly of a rotary wind aircraft is disclosed. The rotary wing aircraft includes at least one engine, and the rotor assembly is coupled to the at least one engine. The rotor assembly includes a first rotor hub, a second rotor hub, and a shaft fairing between the first rotor hub to the second rotor hub, the shaft fairing defined by a chord that varies between the first rotor hub and the second rotor hub.

A rotary wing aircraft that extends along an associated roll axis between a nose region and an aft region and that comprises a fuselage with a front section and a rear section, the rotary wing aircraft comprising: a main rotor that is rotatably mounted at the front section, a shrouded duct that is arranged in the aft region, and a propeller that is rotatably mounted to the shrouded duct, wherein the rear section extends between the front section and the shrouded duct and comprises an asymmetrical cross-sectional profile in direction of the associated roll axis.

A yaw control system for a helicopter having a tailboom and a forward flight mode includes a surface coupled to the tailboom, one or more tail rotors coupled to the surface, a flight control computer implementing a yaw controller having a rudder control module and a tail rotor rotational speed reduction module and a rudder rotatably coupled to the surface. The tail rotor rotational speed reduction module is configured to selectively switch the one or more tail rotors into a rotational speed reduction mode in the helicopter forward flight mode. The rudder control module is configured to rotate the rudder in the rotational speed reduction mode of the one or more tail rotors to control the yaw of the helicopter.

A yaw control system for a helicopter having an airframe that includes a tailboom includes one or more tail rotors rotatably coupled to the tailboom and a flight control computer implementing an airframe protection module. The airframe protection module includes an airframe protection monitoring module configured to monitor one or more flight parameters of the helicopter and an airframe protection command module configured to modify one or more operating parameters of the one or more tail rotors based on the one or more flight parameters of the helicopter, thereby protecting the airframe of the helicopter.

A yaw control system coupled to a tailboom of a helicopter includes tail rotors. The tail rotors include a clockwise tail rotor and a counterclockwise tail rotor. The clockwise tail rotor is configured to rotate in a first rotational direction. The counterclockwise tail rotor is configured to rotate in a second rotational direction, the second rotational direction opposite of the first rotational direction.

An exemplary anti-torque system for a rotorcraft includes a fan located inside of a channel that extends inside of a fuselage from an inlet proximate a forward end of the tail boom to an outlet at an aft end of the tail boom, the outlet is oriented to direct airflow from the channel onto a rudder coupled to a trailing edge of a vertical stabilizer.

An aircraft rotor system including a hub having a hub axis about which the hub is configured to rotate; a plurality of rotor blades configured to extend from the hub and rotate about the hub axis, at least one of the rotor blades rotatable about a respective pitch change axis; wherein the hub is configured to be rotated about the hub axis only by the plurality of rotor blades. Another aspect includes a method of operating the rotor system.