Abstract: A tail rotor for a rotary wing aircraft is located in a laterally directed duct located at the end of a tail cone extending rearward from the aircraft cabin and at the base of an empennage extending upward from the duct. The rotor includes a rotor shaft driveably connected to a power source, a rotor hub connected to the rotor shaft, a rotating control shaft, a stationary control shaft, and an actuator connected to the stationary control shaft for moving the rotating control shaft axially. The rotor hub includes rotor arms each supporting a pitch shaft-blade spar assembly for pivotable movement about a pitch axis. A pitch beam supports flexures, each connected to a pitch arm offset laterally from the associated pitch axis. The flexures driveably connect the pitch arms to the pitch beam and transmit pitch control motion to the blades as the pitch beam moves along the rotor axis. Pitch bearings, on which the pitch shafts turn about the pitch axes, are supported on a rotor hub shell fixed to the rotor hub.

Abstract: A tail rotor for a rotary wing aircraft is located in a laterally directed duct located at the end of a tail cone extending rearward from the aircraft cabin and at the base of an empennage extending upward from the duct. The rotor includes a rotor shaft driveably connected to a power source, a rotor hub connected to the rotor shaft, a rotating control shaft, a stationary control shaft, and an actuator connected to the stationary control shaft for moving the rotating control shaft axially. The rotor hub includes rotor arms each supporting a pitch shaft for pivotable movement about a pitch axis. Each pitch shaft is adapted to support a rotor blade so that its angle of attack changes with movement of the pitch shafts. A pitch beam, located adjacent the rotor hub, supports flexure members, each connected to a pitch shaft eccentric of its pitch axis.

Abstract: A rotor for a rotary wing aircraft includes a rotor shaft driveably connected to a power source, a rotor hub connected to the rotor shaft, rotor arms inclined with respect to a plane perpendicular to the rotor axis and pitch shafts supported on each rotor arm. The rotor arms each support a pitch shaft for pivotable movement about a pitch axis. A pitch beam carries flexures, each connected to a pitch arm at a location offset laterally from the associated pitch axis. The flexures driveably connect the pitch arms to the pitch beam and transmit pitch control motion to the blades as the pitch beam moves along the rotor axis. Each flexure is intentionally displaced by bending radially during installation in a direction that reduces forces among components of the flexure bearings developed during operation.

Abstract: A rotor system according to this invention includes a structurally flexible coupling for transmitting rotor torque and other rotor loads to a rotor hub. The rotor hub is adapted to have rotor blades mounted thereon and is mounted by an elastomeric spherical bearing whose center is located at the rotor center. A flexible coupling made from fiber reinforced resin matrix material, connected to the bearing at a connection located below the bearing center, extends vertically from that location through the bearing to a position located above the center where it is connected to a connecting member fixed to the rotor hub. The flexible coupling is structurally stiff with respect to the mode in which it transmits rotor torque compared to the rotor torque stiffness of the other components. However, the bending stiffness and axial stiffness of the flexible coupling is substantially less compared to the mode in which rotor moments and forces are transmitted from the other components to the rotor shaft.

Abstract: A rotor system according to this invention includes a structurally flexible rotor shaft for transmitting rotor torque and other rotor loads to a rotor hub. The rotor hub is adapted to have rotor blades mounted thereon and is mounted by an elastomeric spherical bearing whose center is located at the rotor center. A flexible shaft made from fiber reinforced resin matrix material, connected to the rotor shaft at a connection located below the bearing center, extends vertically from that location through the bearing to a position located above the bearing center where it is connected to a connecting member fixed to the upper surface of the rotor hub.The flexible shaft is structurally stiff with respect to the mode in which it transmits rotor torque compared to the rotor torque stiffness of the other components.

Abstract: A three-directional vibration isolator, connecting two bodies, which includes spring elements for coupling vibratory forces between the bodies and an inertia assembly for generating inertia forces to attenuate these vibratory forces. The assembly includes a drive member having one end coupled to one body to allow pivotal movement about a first assembly pivot point and an opposite end which extends axially through a tubular member and which is coupled to radially-extending, equiangularly-disposed, inertia arms to allow pivotal movement of the arms about respective first pivot axes orthogonal to the assembly axis. One end of the tubular member is coupled to the other body to allow pivotal movement about a second assembly pivot point and an opposite end thereof is coupled to the inertia arms to allow pivotal movement of the arms about respective second pivot axes parallel to the first pivot axes.

Abstract: A six axis vibration isolation system, which includes four bi-directional vibration isolators, each having a spring arm and an inertia arm which extend along a longitudinal axis between a body and a vibrating mass. The spring arm is pivotally attached to the body by a spherical bearing, and the inertia arm is pivotally attached to both the body and the vibrating mass by spherical bearings, which allow the vibration isolator to attenuate vibrations in any direction orthogonal to its longitudinal axis.

Abstract: A bearingless rotor system has a flexible strap member to which the root of a rotor blade is attached, and a pitch rod aligned with the pitch axis and mounted to the rotor blade root and to a pitch arm, which arm transmits control system variations by way of a pitch link to the pitch rod. Tapered shoes are disposed adjacent the surfaces of the strap and are capable of applying a restoring force to the strap in opposition to flexural displacements of the strap member.

Abstract: A vibration isolation system for a passenger carrying helicopter with which the crew seats in the cockpit area and the floor in the passenger area are decoupled from the airframe thereby isolating the seats and floor from the airframe vibrations. In addition, the fuel tanks of the helicopter are isolated from the airframe so that a force feedback from the fuel tank to the airframe resulting from the changing fuel quantity is effectively eliminated. The system employs nodal isolators which both isolate (decouple) and support the particular structural mass in question.

Abstract: A vibration isolation system wherein a vibrating mass such as a helicopter rotor-transmission assembly is spring coupled to a body to be isolated, such as the helicopter fuselage, at a plurality of coupling locations. Each coupling location includes a weighted lever arm pivotally connected to the vibrating mass and to the body and a coupling spring connected to the weighted lever arm for transmitting the rotor forces of the rotor-transmission assembly to the fuselage through the pivot connections on the lever arm. The coupling spring is in the form of an elongated spring arm connected at one end to the weighted lever arm and at the other end to the body through a pivot link, the latter being required to accommodate shortening of the spring during flexure. The spring forces transmitted to the fuselage through the coupling springs due to linear vibration forces are cancelled at the characteristic rotor frequency by equal and opposite inertial forces produced by the weighted lever arms.

Abstract: A vibration isolation system wherein a vibrating mass such as a helicopter rotor-transmission assembly is spring coupled to a body to be isolated, such as the helicopter fuselage, at a plurality of points. Each coupling point includes, in addition to a coupling spring, a weighted lever arm pivotally connected to the vibrating mass and to the body, with the body-to-lever pivot connection lying between the center of gravity of the arm and the vibrating mass-to-lever pivot connection. The coupling spring is in the form of a torsion spring, e.g., torsion bar, coupled between the body and the lever arm at the pivot connection therebetween. Vibratory forces of a predetermined frequency transmitted from the vibrating mass to the body through the spring are substantially cancelled by inertial forces generated by the lever and applied to the body through the body-to-lever pivot connection, thus isolating the body from the vibrating mass at the predetermined frequency.