Abstract: The rotor blades or wings of the present helicopter rotor structure are interconnected by tension or carrier bars so that diametrically opposite rotor blades or wings form a pair. The tension bars are substantially stiff against bending, but permit some bending. The blade angle bearings are movable in the blade flapping direction, as well as in the blade lead-lag direction. At least one blade angle bearing of a pair of such bearings permits an axial movement of the respective tension or carrier bar, whereby the latter is able to take up bending loads.

Abstract: The blades or wings of a rotary wing aircraft are secured to the rotor head n a non-rigid manner by means of a carrier bar, however, without any flapping hinges and without any lagging hinges. The carrier bar is supported on the rotor head. The connection of each wing to the respective end of the carrier bar is such, that the longitudinal wing axis is excentrically displaced relative to the central longitudinal axis of the carrier bar in the direction in which the forces of the air are effective. The displacement or spacing between the two axes is such that at least a partial compensation of the occurring bending moments is achieved.

Abstract: The present rotor structure for rotary wing aircraft, such as helicopters, s constructed to minimize the mass unbalance which normally occurs due to the lead-lag of the rotor blades or wings. For this purpose all the bearings supporting the rotors on the rotor heads are constructed as bearings permitting an axial movement of the tension bars which interconnect the wings of a pair of wings. In addition, the wing interconnecting bars are bending-resistant and connected with each other at their crossing point by a centering device which is freely movable in the rotor plane and relative to the rotor head. The connection of the bars by the centering device is rigid in the longitudinal, axial direction of the tension bars.

Abstract: An elastomeric bearing for a helicopter rotor in which the laminates of the bearing are shaped and positioned so that the center of hydrostatic pressure generated in each elastomer laminate and the cross-sectional center of gravity of each metal laminate are in alignment so that the integrated load vectors reacted through the metal and elastomer laminates of the bearing in imparting blade centrifugal loads to the hub therethrough are substantially in alignment to thereby prevent the creating of eccentric internal moments and hence avoid life reducing bending and hoop stresses in the metal laminates and unnecessarily high hydrostatic pressures in the elastomer laminates.

Abstract: A helicopter rotor assembly comprises a rotor including a rotor boss and a rotor cup in, and coaxial with, said boss, a plurality of rotor blades each having an integral rigid spindle connecting the blade to the rotor with the spindle axes intersecting at the axis of rotation of the rotor and with the blades being inclined upwardly from the rotor. Articulated joints connect the spindles with the boss and further articulated joints connect the spindles with the cup. The blades are rotatable about the spindle axes and control means is provided for lifting and lowering the rotor boss relative to the cup to vary the inclination of the blades.

Abstract: A rotor blade retention system connects an elongated rotor blade to a rotor hub that is rotatable about its central axis. The connected rotor blade normally extends generally radially from the hub and is rotatable with the hub. The retention system includes a pair of bearings that are interconnected in parallel load transmitting relationship. Both bearings are connected in serial load transmitting relationship with a flap hinge. One bearing is relatively stiff along the longitudinal axis of the rotor blade and is less stiff in directions transverse to the longitudinal blade axis. The other bearing is most stiff in directions transverse to the rotor blade axis and is less stiff along the axis. Both bearings define effective elastic centers which are located along the longitudinal blade axis, but the two elastic centers are spaced from each other. The two bearings accommodate lead-lag motions of the rotor blade.

Abstract: A torsionally compliant helicopter blade having its aerodynamic center axis positioned selectively forward of its center of gravity and elastic axes throughout a selected portion of the blade span so that, during operation, the blade will experience airloading which will induce two per rev torsional deflection of the blade to thereby improve rotor performance by reducing the total power required to drive the rotor.

Abstract: A helicopter rotor includes, for each of a plurality of rotor blades, a generally radially extending flexure member to accommodate blade flap movements, a feathering hinge for pitch change movements and an elastic shear mounting located within the feathering hinge to accommodate rotor blade lead and lag movements. Spaced-apart elastomeric bearings are utilized in the feathering hinge, and the elastic shear mounting is associated with the outer elastomeric bearing and is arranged to be substantially equally resilient in both the lead/lag and flap planes. The arrangement facilitates the incorporation of automatic damping in the lead/lag plane by selection of suitable material for the elastic shear mounting.

Abstract: Each rotor blade is rigidly affixed to a pair of strap members which are also rigidly connected to a rotor hub. Each strap member is defined as an elongated open box beam of rectangular cross section. Each strap member has its open web located on the side of the rectangle opposite that of its associated strap member of a pair. A pitch shaft which is located intermediate the two strap members associated with the given rotor blade, is rigidly attached to that rotor blade, and is rotatably connected with respect to the rotor hub. In alternative configurations, the strap members are configured as various alternative solid or open web designs, but all are configured as pairs having a pitch shaft therebetween.

Abstract: A laminated bearing comprises a plurality of alternating and bonded together layers of elastomeric material and substantially nonextensible material. Each of the layers is a frustroconically shaped annulus that has a pair of frustroconically shaped side surfaces and is concentrically disposed about a common axis extending lengthwise of the bearing. The side surfaces of adjacent layers are bonded to each other such that the larger diameter end of each layer is disposed adjacent to the larger diameter end of another layer. Together, the larger diameter ends of the layers define an annular surface of the bearing. The annular surface formed by the ends of the layers defines, in radial section, an angle with respect to a line which lies normal to the side surfaces of the layers. The direction of the angle or inclination, with respect to the normal line, is toward the smaller diameter ends of the layers with increasing distance along the normal line away from the common axis. Preferably, the angle is about 9.

Abstract: The present invention relates to a rotor arrangement for rotary-wing aircraft, comprising at least one pair of opposite blades mounted on a common one-piece beam, which is twistable, flexible and whose median part rotates with the shaft of the rotor.According to the invention, this arrangement is characterized in that said beam is mounted on the shaft of the rotor by means of an articulation enabling it to pivot, in limited manner, about an axis transverse to said beam and at right angles to said rotor shaft.The invention is applied to rotors for helicopters.

Abstract: A helicopter rotor includes a rotor hub and a plurality of rotor blades, the rotor hub comprising, for each rotor blade, a flexure member extending generally radially from the hub and being flexible in a blade flap plane. A feathering hinge is located at an outer end of the flexure member and includes a cylindrical portion mounted on an extension of the flexure member and resilient means arranged to permit blade lead and lag movements of the cylindrical portion during operation. In a described embodiment, the cylindrical portion is mounted on axially spaced apart bearings comprising an inner part spherical bearing having a geometrical center and an outer parallel bearing, and a resilient elastomer ring is interposed between the outer bearing and the cylindrical portion so as to permit pivotal movement of the cylindrical portion about the geometrical center of the inner bearing.

Abstract: A helicopter rotor having flexible blades mounted to a drive shaft by means of hub arms, wherein opposing blade members are interconnected by a common spar passing across the rotor axis. The spar members are supported from the hub arms by spherical bearing members. The universal freedom of these bearing members provides torsional freedom for blade pitching motions without restricting blade flapping or in-plane bending.

Abstract: A two-bladed semi-rigid type tilt hub teetering rotor for an autogiro. The otor has a spin-up condition in which it has an relatively small blade angle, and an in-flight condition in which the blade angle is relatively high. The rotor is adapted to alter automatically from its spin-up condition to its in-flight condition upon tilting of the hub at take-off.

Abstract: A helicopter rotor having opposed blades interconnected by a common flexible spar which passes across the rotor axis is connected to the drive shaft by clamped hub plates. A spanwise extending torque tube having a pitch horn at its inner end forms a rigid connection with the spar and blade at its outboard end. A centering bearing assembly is positioned at the inner end of the torque tube and spar to react control loads, centralize the torque tube about the spar, and provide pitch, flap, and lead-lag decoupling.

Abstract: A wind turbine having a flexible central beam member supporting aerodynamic blades at opposite ends thereof and fabricated of uni-directional high tensile strength material bonded together into beam form so that the beam is lightweight, and has high tensile strength to carry the blade centrifugal loads, low shear modulus to permit torsional twisting thereof for turbine speed control purposes, and adequate bending stiffness to permit out-of-plane deflection thereof for turbine yard control purposes. A selectively off-set weighted pendulum member is pivotally connected to the turbine and connected to the beam or blade so as to cause torsional twisting thereof in response to centrifugal loading of the pendulum member for turbine speed control purposes.

Abstract: This invention relates to helicopter rotors having three or more blades and of the type having a hollow rotor drive shaft and a control column positioned within the hollow shaft arranged to support a spider assembly at its upper end through which control movements are transmitted to the rotor. In the present invention, the inner ends of at least two of the arms of the spider are retained in fixed relationship and the outer end of each arm is connected to its respective feathering hinge through a vertical pivot located on an axis at an operational radius not greater than a radius of a point about which blade lead/lag movements occur. This arrangement serves to establish a virtual floating fulcrum about which the control column is tilted during operation to impart control movements, and thereby eliminates the complicated mechanical support means that are a feature of prior rotors of this type.

Abstract: The invention relates to a two-bladed tail rotor arrangement for gyroplanes and helicopters, comprising two plates fixed to a rotary shaft, between which are embedded the median portion of a flat flexible spar. On the ends of the said spar are fitted two shells which form the rotor blades and whose cross-section evolves in the blade root area to become circular, whereby the said shells are terminated by cylindrical sleeves fixed by bonding to flanges which are connected by elastic blocks to two plates. The rotor boss assembly can be provided with a cylindrical fairing.

Abstract: A helicopter cross beam rotor is shown including upper and low coaxial composite blade spars at right angles secured by tension bolts which pass through the composite spars and are held by threaded nuts to a rotor hub at the upper end of a rotor drive shaft. A metal cap plate above the upper spar and a spar-to-spar filler piece are also provided. Torque between the spars and the rotor hub is reacted by intermeshing ribs and grooves on the confronting faces of the hub, the filler piece and the cap plate. The bolt holes in the composite spars are oversize so that the bolts do not react torque between the rotor hub and the composite spars.

Abstract: A variable pitch blade and blade mount which is suitable for propellers, fans and the like and which has improved impact resistance. The invention is particularly directed to composite fan blades and blade mounting arrangements wherein the blades are permitted to pivot relative to a turbine hub about an axis generally parallel to the centerline of the engine upon impact of a large foreign object, such as a bird. By thus providing for the pivoting of the blades upon impact, centrifugal force recovery becomes the principal energy absorbing mechanism and a blade having improved impact strength is obtained.

Abstract: A flexure for connecting the root end of a rotor end of a rotor blade to a rotor hub in a bearingless rotor assembly. The flexure inherently induces a change in pitch angle in accordance with a change in flap angle. The flexure, which may form an integral portion of the rotor blade, is constructed of a composite material made of fibers secured to one another by a bonding agent. The fibers are arranged in two sets. The variation of the blade pitch angle in accordance with the blade flap angle is accomplished by either varying the number of fibers between the two sets or varying the angle of each set to the longitudinal axis of the flexure, or both.

Abstract: This invention provides a rotor hub for a rotary wing aircraft in which elastomeric bearing means are utilized to transmit centrifugal loads and blade pitch, flap and lead lag movements, and in which the blades are foldable about a pivot located outboard of the elastomeric bearing means between extended and folded positions. Locking means are provided to ensure that no deflection of the elastomeric bearing means occurs during the folding operation.

Abstract: A rotor blade retention system connects an elongated rotor blade to a rotor hub that is rotatable about its central axis. The connected rotor blade normally extends generally radially from the hub and is rotatable with the hub. The retention system includes at least three laminated elastomeric bearings connected together in serial compression load transmitting relationship. Each laminated bearing includes a plurality of alternating and bonded together layers of elastomeric material and substantially inextensible material. The layers of each of the serially interconnected bearings are at least partially inclined relative to the longitudinal axis of the rotor blade. In section taken radially of the longitudinal axis of the blade, at least a portion of each layer of each bearing projects longitudinally toward an end of the rotor blade. Preferably, only one of the serially interconnected bearings is rigidly connected to the rotor blade.

Abstract: A torsionally compliant helicopter rotor blade with maximum blade torsional flexibility at the blade tip portion and so shaped at the blade root portion that the locus of shear centers and the locus of centers of lift are substantially coincident, and so shaped at the tip portion so that the locus of shear centers is selectively forward of the locus of centers of lift to establish an aerodynamic restoring moment in response to blade tip torsional excursions, thereby improving blade torsional stability.

Abstract: This invention relates to a semi-rigid rotor of the type in which each rotor blade is attached to a hub through a flexure member comprising an inner part which accommodates flapping movements and an outer part which accommodates lead/lag movements. In the arrangement of the present invention the outer part of each flexure member comprises a spindle extending from the inner part and an arm extending from a housing rotationally mounted on the spindle, the arm extending outwardly to an outer end arranged for connection to a rotor blade and spaced-apart radially from an outer end of the spindle. A tie-bar interconnects the outer end of the arm and the spindle, and means are provided to rotate the housing to effect pitch changes of the rotor blade during operation.

Abstract: A rotor for a rotating wing aircraft has a star-shaped hub each arm of which supports a blade. The yoke between each blade and arm is a two tine fork constituted by a continuation of the blade root.

Abstract: A propeller assembly comprises a rotatable drive shaft and two separate blade subassemblies resiliently coupled to and driven by the shaft. Each blade subassembly has a pair of interconnected propeller blades extending in opposite directions radially of the shaft. The blade subassemblies are disposed in parallel planes with the blades of one subassembly oriented transversely of the blades of the other subassembly. Rotational movement of the shaft is transmitted to the blade subassemblies through viscoelastic material which is torsionally loaded and stressed in shear. The viscoelastic material resiliently permits and damps in plane or lead-lag movement of each blade subassembly relative to the drive shaft. The subassemblies are also interconnected so that the viscoelastic material resiliently permits and damps relative in-plane movement between the subassemblies.

Abstract: Improved stability is provided in a hingeless helicopter rotor by inclining the principal elastic flexural axes and coupling pitching of the rotor blade with the lead-lag bending of the blade. The primary elastic flex axes can be inclined by constructing the blade of materials that display non-uniform stiffness and the specification describes various cross section distributions and the inclined flex axes resulting therefrom. Also described are arrangements for varying the pitch of the rotor blade in a predetermined relationship with lead-lag bending of the blade, i.e., bending of the blade in a plane parallel to its plane of rotation.

Abstract: An improved rotor for a helicopter comprises a yoke at the inner end of each arm engaging the rotor hub by way of a spherical abutment.

Abstract: A grip-yoke assembly for attaching a helicopter blade to the mast of the helicopter rotor having a conventional primary coupling to carry the centrifugal loads and a redundant path operative should the primary coupling fail to insure continued operability of the blade. In one embodiment, the redundant load path has a bearing surface formed on the inboard end of the grip and a corresponding thrust bearing mounted on an inboard yoke fitting for engagement with the bearing surface upon failure of the coupling. In an alternative embodiment, a bearing surface is formed on an outboard grip fitting and a corresponding thrust bearing is supported on the yoke outboard of the grip fitting.

Abstract: A helicopter rotor hub is provided with a center plate and a plurality of arms projecting from the center plate. Each of the projecting arms has a slot for receiving a flexible element that is connected to a spindle and grip that supports the rotor blades. The rotor blades can accomplish the movements of flapping and lag by allowing the center plate to have a low stiffness in the vertical plane when the center plate lies in a horizontal plane, and the flexible element a low stiffness in the horizontal plane when the flexible elements lie in the vertical plane, thereby acting as virtual hinges. This allows for the possibility of locating the vertical hinges at an equal distance from the rotor axis, and the pitch variation hinge a small distance from the other hinges, allowing for a relatively small dimension of the hub.

Abstract: A fully articulated helicopter rotor having an elastomeric type main bearing which is reactive of all blade motions about the intersecting blade pitch change, lead-lag, and coning axes, including blade droop supporting and limiting members for static and dynamic operating conditions wherein coupling influences between the separate blade motions are precluded. In reacting these blade weight loadings and dynamic thrust forces, the droop members specifically provide full area contact bearing surfaces to distribute the large forces from the blades into the rotor hub proper while avoiding scuffing or rolling contact between the parts, and the high bearing stresses which would result from either point or line contact only.