Abstract: A helicopter rotor system with a plurality of identical rotor blades each of which includes a skin that forms an interior region, a counterweight rod and a bundle of longitudinally-extending fibers in the region. The bundle continues outside of the region, and there it includes a bight portion with a pair of arms and a bend. The fibers in the region are continuations of the fibers in the bight portion. A torque tube is attached to the counterweight rod, and a bearing stabilizes the torque tube relative to the mast, but does not transfer any appreciable centrifugal load. This bearing permits rotation (feathering) of the torque tube around its own axis, and lateral movement in any direction from the torque tube axis, around the center of this bearing (lead lag, and flapping). The bight portion is progressively shaped from a single flat portion bent directly around the mast, through a pair of separate channel sections to a bundle adjacent to the counterbalance rod.

Abstract: The wing blades of a helicopter rotor each are connected to the rotor hub a connection, e.g. a spar being .fwdarw..rarw. including a hinge which is at least fictitious to permit lead-lag movements of the blades <yielding relative to torsion to permit the blade angle adjustment>. A rod, which is stiff in the lead-lag direction and yielding against torsion, is connected in parallel to the connection between the blade root and the rotor hub. One connection of the rod is rigid, for example the connection to the blade root. The other connection of the rod is elastically yielding substantially only in the plane of the rotor whereby a substantial damping of blade movements in the lead-lag direction is accomplished.

Abstract: In a helicopter tail rotor of flexrotor or, composite bearingless rotor design, a control wheel member is positioned in spaced relationship to the torque tube at the blade inner end and is connected thereto by pivotal push-pull rods connected at one of their ends to the control wheel member and at their opposite ends to the leading edge and trailing edge of the torque tube so that, as the control wheel member is selectively caused to rotate relative to the blade, one push-pull rod pulls upon the torque tube while the other push-pull rod pushes upon the torque tube to cause the torque tube to rotate, and hence the flexible spar to which it is attached to twist to thereby selectively change the blade pitch angle.

Abstract: A helicopter including a driven rotor assembly provided with a hub having oscillatable rotor blades extending outwardly therefrom and axially spaced portions of the hub having outer peripheral portions of a pair of annular flexible and elastic supporting diaphragms anchored relative thereto. Inner peripheral portions of the diaphragms are deflected and stretched toward each other and anchored to a supporting flange carried by a central rotary drive shaft of the rotor assembly. A sleeve is longitudinally shiftably mounted on the shaft below the rotor assembly and supports, through the utilization of a flexible and resilient diaphragm, a larger sleeve structure therefrom for universal angular displacement of the sleeve structure relative to the sleeve. The sleeve structure includes control arms operatively connected to the rotor blades for oscillation of the latter in response to axial shifting of the sleeve structure relative to the sleeve.

Abstract: A helicopter rotor has at least one pair of diametrically opposed rotor blades interconnected by a strap member flexible in torsion and in a plane perpendicular to a plane of rotation and stiff in a plane coincident with the plane of rotation. A torsionally flexible tie-bar having a tensile elastic modulus greater than that of the strap member is extended between pivotal attachments adjacent opposed ends of the interconnecting strap member.In operation, a major portion of centrifugal loads caused by the rotating blades is carried by the tie-bar.

Abstract: The present four-blade rotor is made up of two blade pairs, each blade pair aving two rotor blades arranged diametrically opposite one another. The blades of each blade pair are coupled to each other by means of a coupling loop for taking up centrifugal forces produced by the rotation of the blades. The present rotor system also has a centering device including a centering body and tension straps for each coupling loop. The tension straps connect the respective loop end to the centering body whereby the two coupling loops may be centered in the rotor head practically without play and without substantially limiting the free movement of the coupling loops.

Abstract: In a helicopter rotor, a blade control linkage is externally supported on the rotor hub and connected to the root end of a torque tube to provide torsion inputs to the blade by twisting the flexible spar member, which is enveloped by the torque tube and joined to the torque tube at a predetermined blade radial location. The linkage forms a parallelogram with the torque tube, and short vertical ball joint mounted links incline in two directions to accommodate blade lead/lag and flapping motions without introducing pitch coupling.

Abstract: A variable-pitch, multi-blade propeller specially usable as a rear rotor of a rotary-wing aircraft and a process for manufacturing the same are described. The propeller comprises a number of pairs of blades emanating from a central hub, each pair comprising a single elongate strip secured at its center to the hub. The strip is composed of two flat bundles of fibres and defining an aperture for a sliding shaft at their center. The shaft is used to control the pitch angles of the blades and aerodynamic blade shells are secured to the fibre bundles by adhesive synthetic cellular or foam material.

Abstract: A composite bearingless helicopter rotor system utilizes one single and only flexible strap as at least the principal wing support, and also preferably has also a blade pitch shaft. The line of shear centers of the flexible strap, the line of shear centers of the blade pitch shaft, and the pitch axis each lie somewhere along the one straight line, or substantially so.The cross section of the flexible strap may vary but in each case it is one which is asymmetrical relative to a line through its center of gravity and parallel to the axis of rotation of a rotor, and in each case the line of shear centers of the flexible strap, the line of shear centers of the blade pitch shaft and the pitch axis all are spaced from the line of centers of gravity of the flexible strap. A number of examples of varying specific overall configurations of flex straps and blade pitch shaft will be found described and illustrated herein, of which an example is that in FIG.

Abstract: A rotor blade has a neck section which connects the blade proper to a rotor ead at the blade root. The neck section is flexible against bending in the lead-lag direction and in the flapping direction. A carrier member is located alongside or inside the neck section but spaced from the neck section. The carrier member is resistant against bending at least in the lead-lag direction or in the flapping direction. The carrier member is rigidly connected at its one end to the blade proper. A layer of a damping material is operatively interposed between the carrier member and the neck section, preferably at the blade root end of the neck section, whereby blade vibrations preferably in the lead-lag direction are damped and substantially prevented from entering into the rotor head.

Abstract: The present four-blade rotor structure comprises two pairs of rotor blades. iametrically opposite each other located blades form a pair and the blades of a pair are connected to each other by coupling belts which are tension resistant and torsionally yielding. One coupling belt extends substantially horizontally whereas the other extends substantially vertically. The coupling belts are centered in the rotor head by respective centering bodies. The centering bodies are connected to their respective belt by bearing elements capable of taking up pressure loads while simultaneously permitting a blade angle adjustment. In a modification the bearings may be slide bearings.

Abstract: The present hingeless rotor structure, especially for rotary wing aircraft, omprises at least one pair of rotor blades, whereby the blades of a pair are arranged diametrically opposite each other. The blades are secured to a rotor head for proper blade angle adjustment. Each blade has its root or radially inner end secured in a blade root sleeve which in turn is held in a respective blade angle bearing bushing. The blades of a pair are interconnected by a tension resistant, torsionally yielding member. One bearing which is pressure loadable in the direction of the longitudinal blade axis is provided for each blade pair between one of the respective blade root sleeves and the corresponding blade angle bearing bushing. The tension resistant, torsionally yielding member is capable of a certain stretching or elongation during operation.

Abstract: The present rotor for rotary wing aircraft is of the type which is free of flapping hinges as well as free of lead-lag hinges. Such rotor shall have a simple structure and a small structural weight while simultaneously having a high operational reliability. To this end the rotor hub comprises upper and lower support or carrier plates made of a fiber compound material arranged in such a manner that the fibers extend substantially radially. The upper and lower support plates are spaced from each other by thrust arms or lands and the blade angle bearings are supported between the carrier plates of a fiber compound material.

Abstract: A rotor for a rotary wing aircraft includes a rotor head and an even number of rotor blades arranged in pairs about the rotor head. The rotor blades of each pair are located diametrically opposite each other and each blade has a root end positioned radially inwardly toward the head. Bearings carried by the rotor head pivotally support each of the rotor blades. A torsionally elastic connection member extends between and connects the roots of a pair of rotor blades, and the connection member is mounted at its longitudinal center in the rotor head for pivotal movement about its longitudinal axis.

Abstract: A pitch change slide is mounted for longitudinal movement on a propeller shaft hub adapter in turn secured to the engine shaft of an aircraft engine, the said slide carrying a plurality of toothed racks each engaged with a spur gear on the base of one of a plurality of rotatably mounted propeller blades. Reciprocation of the pitch change slide changes the pitch of the propeller blades. The pitch change slide carries a coiled spring. A spring pressure slide, mounted for longitudinal movement on the propeller shaft hub adapter, has a flange bearing against the coiled spring, and is reciprocable on the propeller shaft hub adapter through a control rod operable from the aircraft cabin, thereby to adjust the degree of compression of the spring. Weights are mounted on the propeller blades and generate centrifugal force as the engine shaft turns, the said centrifugal force tending to rotate and change the pitch of the propeller blades.

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 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: A rotor blade extended radially from a hub, characterized by an elongated spar and a plurality of axially aligned shells pivotally mounted on the spar, each having an aerodynamic center located in trailing relation with the spar and supported thereby for simultaneous axial and angular displacement as centrifugal forces are applied thereto, and a pitch controller including a plurality of pivotal pitch limiting arms transversely related to the spar, each being characterized by a cam surface defined along one edge thereof, engaging in supporting relation a cam follower of a truck pivotally connected to a shell and supported thereby for pivotal motion about an axis coincident with a radius of said spar, and a push-pull link interconnecting the arms for imparting simultaneous pivotal motion thereto, whereby the angular relationship of the arms to the spar is varied for varying the motion of the trucks along the arms for thus limiting the pitch of the segments about the spar.

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 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: 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: 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: 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 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 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.