Abstract: A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

Abstract: The rotor blades of a rotary wing aircraft are mounted at their blade roots pon a rotor head formed as an integral body of composite fiber material shaped to define a plurality of bifurcated rotor blade support arms between which the blade roots are mounted. Each of the blades is formed, at least in the region of the blade roots, with a laminated configuration including at least two layers formed with a fiber loop having a unidirectional fiber orientation extending longitudinally of the rotor blade and about a load-bearing connection between the blade root and the rotor head. An intermediate layer having a crosswise fiber orientation is provided between each of the at least two layers of the blade root which integrally joins the two layers and the fiber loop is enclosed by support members at its longitudinal edges at the inside and outside thereof at least in the region of the load-bearing connection.

Abstract: A control for a helicopter tail rotor where inboard twist sections on opposite sides of a central hub section are adjacent to pitch horns mounted outboard the margins of the twist sections and extend to a negative delta.sub.3 connection point located at the virtual bending axis of each twist section. The rotor teeters on the tail mast with the span axis of the rotor at an angle of the order of 30.degree. to 45.degree. from the teetering 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 system of rotatably and pivotally mounted radially extended bent supports for radially extending windmill rotor vanes in combination with axially movable radially extended control struts connected to the vanes with semi-automatic and automatic torque and other sensing and servo units provide automatic adjustment of the windmill vanes relative to their axes of rotation to produce mechanical output at constant torque or at constant speed or electrical quantities dependent thereon.

Abstract: The wings of a rotary wing aircraft comprise, for example, four wing blades orming two pairs of wing blades whereby the blades of a pair are located diametrically opposite each other. The blades of a pair are connected to each other by a spar extending from wing blade to wing blade. The spar is operatively secured to the rotor head. Each spar has between the rotor head and the respective wing blade a zone with a torsion yieldability larger than in the spar outside said zone. A beam stiff against bending, bridges the zone, referred to as a torque soft zone, from the wing blade toward the rotor head except for a small flexible section between the rotor head and the radially inner end of the beam. The flexible section permits the blade flapping movements and the blade lead-lag movements.

Abstract: The wing blades of a hingeless and bearingless multiblade rotor are connected to a substantially rigid rotor hub by spar sections elastically twistable and bendable in the flapping direction and in the lead-lag direction. The mounting positions on the periphery of the rotor hub for connection of the spar sections of the respective blades are off-set relative to the angular position of the corresponding blades to which they are connected. Further, the mounting positions for the spar sections of each rotor blade are situated on the periphery of the half side or far side of the rotor hub, facing away from the respective rotor blade.

Abstract: The multi-blade articulated rotor for helicopters, comprises a hub connected to a shaft rotatable substantially about a vertical axis, the hub being in the form of a plate comprising a plurality of perforations, each of which defines a bridge of material of said plate between a part of the edge of said perforation and a part of the edge of said plate; a plurality of yokes, each of which is substantially of U shape and comprises a pair of substantially parallel arms and a base element which connects together one end of said arms, the other end of the arms being connected to one of said blades, said base element being inserted into one of said perforations in the hub; a plurality of elastomer bearings, each of which is disposed between said base element of a yoke and the corresponding hub bridge; and means for limiting the amplitude of the swivel movement which each of said yokes can make substantially in a vertical plane.

Abstract: A blade retention system for use in a fully articulated rotor head of a rotary wing aircraft is described. The retention system comprises a separate elastomeric bearing means for carrying loads in compression and accommodating motions about the respective flapping, lead-lag, and pitching axes of the rotor head in shear for each type of motion about the respective flapping, lead-lag and pitching axes of the rotor head.

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: The neck of a hingeless helicopter rotor wing blade is provided with a damping device effective to dampen lead-lag movements of the rotor wing blade. For this purpose the damping device comprises at least two stiff plates secured to opposite sides of the blade neck by a plurality of elastomeric members glued or bonded to the respective stiff plate and to the blade neck at spaced intervals. The difference of deformation between the stiff plates and the blade neck causes a deformation of the individual members in directions substantially across the longitudinal blade direction (in lead-lag plane). The spacings between adjacent members are located where the damping action is inherently low.

Abstract: A flexbeam having matched in-plane and out-of-plane stiffness is described extending at least partway between the tips of a pair of rotor blades bonded thereto. The flexbeam so constituted produces a blade system with a primary in-plane frequency less than the primary forcing frequency. The matched stiffness of the flexbeam is provided by admixing, either compositionally or by laminating, materials of differing flexibilities to produce a high damping material of symmetrical stiffness.

Abstract: A hingeless helicopter rotor including an aerodynamically shaped hub having a flexible diaphragm as its bottom wall, which diaphragm is connected to the rotor drive shaft and is elastically deformable in response to blade loading to tilt in any direction with respect to the axis of rotation, and further having at least three equally spaced helicopter blades projecting from and supported from within the hub for rotation therewith and for flexing with respect thereto in response to blade loading so that the flexible hub and the blades coact to produce a low equivalent offset rotor and minimized Coriolis effect.

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: A hub assembly for a helicopter rotor system having a monolithic thin-wall hub shell made from composite material and including centrally apertured upper and lower wall portions integrally joined at the outer periphery of the shell and spaced apart at inner regions. The upper and lower wall portions cooperate to define a plurality of bearing sockets angularly spaced relative to the axis of rotation and connecting webs extending between angularly adjacent sockets. Elastomeric blade retaining bearing assemblies supported within the sockets retain and support rotor blades for articulate movement. Each bearing assembly has a seating surface which cooperates with an associated bearing surface on the socket in which it is contained to prevent relative rotation therebetween. Mounting flanges on the helicopter rotor shaft and retaining flanges on the hub shell are arranged to permit the rotor system to be lowered on the rotor shaft when the retaining flanges are disconnected from the mounting flanges.

Abstract: A helicopter tail rotor structure includes a thin, flat, tension-bearing strap of fibers extending spanwise, and is to be centrally secured by a hub to a helicopter tail mast. Flex sections are formed inboard of substantially equally divided portions of said fibers which extend as top and bottom blade spars from the outboard margins of the flex sections. Preferably, the planes of the flex sections and the planes of the spars are oriented at predetermined nose-up twist angles, one relative to the other.

Abstract: Rotary-wing aircraft rotor comprising a rigid hub coupled to the root of each blade in which a trailing return brace comprises a stack of metal plates alternating with plates of visco-elastic material the ends of which being coupled via a ball joint respectively to the root of one blade and to a place of the hub such that the brace is always slightly inclined.

Abstract: A helicopter rotor having an even number of articulated blades wherein opposing blades are interconnected by a common spar passing across the rotor axis. Pitch change is introduced to the blade at the spar-blade attachment joint through a torque member connected at its outboard end to the blade joint and including a control horn at its inner end to receive pitch inputs. Drive for the rotor and support for each blade is provided by a spherical bearing directly connecting the torque member to the blade associated hub arm.

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 helicopter rotor includes a rotor head arranged to support a plurality of rotor blades for rotation about an axis. The rotor head comprises a generally hollow structure, and each rotor blade is supported by an elastomeric bearing arranged to permit blade flap, lead/lag and feathering movements. A resilient support means is housed within the structure and is operatively associated with each rotor blade so as to provide controlled restraint of rotor blade movements in the blade flap plane. In the illustrated embodiment, the support means comprises interconnected inner and outer elastomeric assemblies, the outer assembly being connected to each rotor blade through a common elastomeric lead/lag damper unit which provides inter-blade damping of blade lead/lag movements. The outer elastomeric assembly also provides an automatic blade droop stop.

Abstract: The stringer of a rotor blade assembly is mounted on the hub plates of a driveshaft by a two pair of conically elastic studs which space the stringer from the plates. The cylindrical sleeve root of the blade shell is mounted to the hub by a resilient ball joint.

Abstract: A rotor yoke (10) for coupling helicopter blades to a rotatable support mast (12) utilizes a novel laminated construction. Layers (30) of unidirectional fibers and layers (32) of bias ply fibers are arranged in alternating sequence to form an elongate loop structure. At least some of the bias ply layers (32) extend between the sides of the loop to form a transverse central section (20). Further, at least some of the bias ply layers (32) include gaps to provide flexure areas (24) in the sides of the yoke (10).

Abstract: The present hingeless rotor system for helicopters has carrier spars or b each of which is subdivided into three functional sections substantially forming the blade neck connecting the lift producing portion of the respective rotor blade to the rotor mast. The carrier spar sections form a single structural blade neck member extending for about two tenths of the rotor radius from the rotor mast to the lift producing blade portions. About one half of the length of the blade neck adjacent to the rotor mast form the connecting zone proper. The spar sections comprise bands forming respective loops in the connecting zone proper. Two of the band loops are connected one above the other and a third band loop is displaced in the direction of rotation of the rotor from the first mentioned band loops. The third band loop is releasably connected to the rotor mast to allow a folding of the respective rotor blade. The spar sections are interconnected by shear resistant bridging webs having a T- or X cross-section.

Abstract: In a fully articulated helicopter rotor head, utilizing an elastomeric bearing to support each rotor blade and react centrifugal flight loads, a blade restraint, effective in three axes is provided for use during blade folding for aircraft stowage purposes. The restraint allows the blade to be folded through a predetermined fold plane, and held there while preventing or minimizing deflection of the elastomeric bearing.

Abstract: The invention relates to a rotor, specially for a helicopter. This rotor comprises a plurality of blades connected to a rotor hub by flexible, twistable, substantially radial strips, surrounded by tubular rigid sleeves. Rigid rings are secured to the inner ends of the tubular sleeves. Spherical ball and socket joint members are inserted between each radial strip and the rigid ring. The joint members are associated with frequency adaptors for drag movements of the corresponding blade.

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 helicopter rotor hub assembly (10) in which a blade grip (30) extends inboard of a yoke (14) and transfers centrifugal forces to the yoke (14) through a spherical elastomeric bearing (38). Pitch change of the grip (30) and blade (32) is accommodated by the spherical elastomeric bearing (38) which also acts as the pivot point for lead-lag motion of the blade (32) and grip (30). A lead-lag damper (22) is located inboard of the elastomeric bearing (38) and is connected between one end of the grip (30) spaced away from the lead-lag pivot and the yoke (14) for damping the lead-lag motion between the grip (30) and yoke (14).

Abstract: A rotor blade formed of a fiber-reinforced plastic material is constructed for the absorption of at least one of longitudinal forces and bending forces. The interior of the blade is formed of an elongated bundle of fiber strands forming a loop intermediate its ends. The loop defines one end of the longitudinally extending blade. The bundle has two limb portions extending from the loop and forming, adjacent the loop, a transition portion followed by a neck portion and then a blade portion. A skin encloses the blade outwardly from the loop. A layer of fiber strands extends around the outer surface of the loop and between the skin and the limb portions at least in the transition portion. In the region of the loop the fiber strands extend in parallel relation with the fiber strands in the bundle, however, in the transition portion the fiber strands in the layer extend angularly across the longitudinal axis of the blade.

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: A hub assembly for a helicopter rotor system having a monolithic thin-wall hub shell made from composite material and including centrally apertured upper and lower wall portions integrally joined at the outer periphery of the shell and spaced apart at inner regions. The upper and lower wall portions cooperate to define a plurality of bearing sockets angularly spaced relative to the axis of rotation and connecting webs extending between angularly adjacent sockets. Elastomeric blade retaining bearing assemblies supported within the sockets retain and support rotor blades for articulate movement. Each bearing assembly has a seating surface which cooperates with an associated bearing surface on the socket in which it is contained to prevent relative rotation therebetween. Mounting flanges on the helicopter rotor shaft and retaining flanges on the hub shell are arranged to permit the rotor system to be lowered on the rotor shaft when the retaining flanges are disconnected from the mounting flanges.

Abstract: A helicopter rotor includes a rotor head having, for each of a plurality of rotor blades, an elastomeric bearing and a damper that is arranged to provide controlled restraint of rotor blade movement in both the flap and lead/lag planes. The damper can be arranged to exhibit either substantially equal stiffness in both operational planes or any desired stiffness ratio. In a preferred embodiment of the latter arrangement, the desired stiffness in the respective planes are provided by separate components incorporated in the single damper. The damper may be situated either inboard or outboard of the elastomeric bearing.

Abstract: A helicopeter rotor blade fabricated from laminated fiber-reinforced resin includes a blade root end attachment to the rotor hub that provides a structural extension capable of developing chordwise bending moment continuity across a single-pin joint. The extension is a spanwise continuation of the nose block and heel portions of the spar and continues inboard of the blade attachment pin about which the primary axial load-carrying portions of the spar are wrapped. The structural extension is formed as an integral part of the blade spar without secondary bonding or the use of pre-formed fittings.

Abstract: A cross-beam helicopter rotor in which the torque tube enveloping the flexible spar is supported in relation thereto by an elastomeric primary snubber which is readily replaceable in the field and which utilizes a snubber retainer plate bonded to the spar with an elastomer layer of selected shape factor so that the retainer plate remains adhered to the spar while accommodating all blade and spar pitch and flapping motions and so that the retainer plate elastomer layer is substantially more durable than the elastomer layers of the primary snubber. This primary snubber may be used in combination with an auxiliary snubber.

Abstract: Apparatus to center and compressively load a spherical elastomeric bearing about its static apex during helicopter rotor static mode, which centering means is adjustable from a station external of the rotor and is operable to be out of contact during helicopter rotor dynamic mode.

Abstract: A semi-articulated flexstrap for use in connecting a rotor blade to the hub of a helicopter rotor is disclosed. The flexstrap includes a series of straps which alternatingly crisscross at a point between the blade and hub. The straps are substantially parallel to the plane of rotation of the rotor at the crossover point and unrestrained so as to permit relative movement between the straps. The relative movement of the straps of articulation of the flexstrap in the plane of rotation of the rotor permits lead lag motion of the rotor blade to occur.

Abstract: A helicopter rotor having one or more blades mounted for rotation with the rotor hub and each supported therefrom by an elastomeric bearing, and having a lead-lag damper connected to the blade and the hub and extending substantially parallel to the blade axis, and including the improvement of apparatus for preventing tension loading of the elastomeric bearing as the blade moves radially inwardly as a result of rotor braking.

Abstract: This invention is concerned with helicopter rotor control systems which hitherto have tended to comprise complex assemblies which are costly to manufacture and maintain and which are vulnerable to external damage.A helicopter rotor is disclosed in which each of a plurality of radially extending rotor blades is attached to the outer end of an individual spindle 19 having its inner end protruding into the interior of a hollow rotor hub structure 12 and supported by bearing means 21 arranged to permit rotational movement of the spindle 19 about its axis. A pitch control lever 22 is attached to the inner end of each spindle 19 and is articulated, through a universal joint, to the upper end of an individual connecting rod 38, 39, 40 and 41, the lower ends of the connecting rods being attached to a common housing 42 having independently rotatable means for connection to helicopter flying controls.

Abstract: A yoke for coupling helicopter blades to a mast is provided. The yoke comprises a long oval loop of glass fibers embedded in a cured adhesive to form a solid strap. The side portions of the loop are reinforced with layers of bias ply glass fibers arranged in parallel planes. Structure is provided to couple to the side portions of the loop for attachment to the mast.

Abstract: The invention relates to a rotor, specially for a gyroplane. The rotor comprises elongated connecting members respectively inserted between the rotor hub and the rotor blades. Each connecting member comprises a bundle of fibres having a high mechanical strength and agglomerated by a vulcanized elastomer at least in the mid part of the fibre bundle. A rigid tubular sleeve extends in a spaced and surrounding relationship to each elongated connecting member. Each tubular sleeve has an outer end connected to the root part of the respective blade and an inner end with a lateral lug articulated to the blade pitch control lever. An annular elastomer member is inserted in the annular space between the inner end of each tubular sleeve and the corresponding end of the respective connecting member.

Abstract: A flexible spherical bearing, comprising two end pieces connected by a stack of interconnected alternate layers of a flexible material, such as elastomer, and of a strong material, such as metallic material and at least one cavity filled with an incompressible fluid and extending between the two end pieces without the interposition of elastomer. Such a bearing is used for connecting a helicopter rotor blade to the rotor hub of this helicopter.

Abstract: The invention relates to a variable-pitch rotor, specially for a rotary-wing aircraft. Each blade of the rotor is connected to the hub by a flexible connecting member comprising a radial bundle of fibres, each agglomerated by a resin and secured together by a vulcanized elastomer. A rigid tubular sleeve surrounds the connecting member without contact thereto. The outer end of the tubular sleeve is secured to the root part of the blade and its inner end is secured to a rigid ring, to which a blade pitch control lever is externally articulated. Spherical ball and socket joint members are inserted between the rigid ring and rigid parts of the rotor hub. Frequency adaptors are associated with the ball and socket joint members.

Abstract: A helicopter main rotor has an improved fairing enclosing the rotor hub and blade root area for drag and vibration reduction purposes. The fairing has peripheral cutouts through which the blades project provided with rounded lips on the rim of the cutouts to streamline air flowing in and out of the fairing through the cutouts. Internal partitions divide the fairing into chambers, each of which subtends one cutout, thus preventing flow of air through the fairing and attendant drag caused thereby. The rotor pylon is provided with a well through which the rotor drive shaft projects having a rounded lip adjacent the fairing to produce streamline airflow out of the well.

Abstract: In a helicopter rotor in which the blades are supported for rotation and articulation from the hub by elastomeric bearings and including a lead-lag damper which acts to cause radially inward blade motion during rotor braking and including the improvement of utilizing members which move pivotally in response to centrifugal force and which serve blade flapping and droop stop functions both statically and dynamically and which further are programmed as a function of rotor speed to prevent or limit radial inward motion of the blade during the rotor braking operation.

Abstract: This invention relates to helicopter rotors in which the rotor blades are supported by flexure members and resilient means to permit flap and lead/lag movements.Hitherto such support means have been subjected to centrifugal forces thus complicating their design and requiring compromises such that optimum properties in flap and lead/lag planes have been unattainable.In this invention, each blade is attached by an individual spindle 19 supported in an elastomeric bearing 21 secured in a hollow rotor hub 12. Arms 26, flexible in a flapping plane, extend from the rotor hub 12 and a bearing 46 at the outer end of each spindle is attached to its associated arms through resilient means 30 to permit lead/lag movement of the spindle 19 relative the arms 26.In operation, centrifugal loads are transmitted to the hub 12 so that the arms 26 and resilient means 30 can be designed to provide optimum properties in the flap and lead/lag planes.

Abstract: A rotor, especially for rotary wing aircraft, is constructed without flapping hinges and without lead-lag hinges. The rotor comprises a rigid rotor head and rotor blades secured to the rotor head by flexible coupling rods, for example, made of fiber reinforced composite material. One end of each rod is secured to the rotor head. The other end of each rod is secured to the root of the respective rotor blade. The rods are so arranged that their central longitudinal axes coincide with a generatrix of two coaxial cones having a central axis. One of the cones is located with its base in the respective rotor blade while the other cone is located with its base in the rotor head. This type of structure is surprisingly simple, yet capable of transferring substantial forces between the rotor head on the one hand and the rotor blades on the other hand.

Abstract: A rotor hub for a helicopter having a hum member rotatably mounted to a rr mast stationarily attached to the fuselage of a helicopter and forming an air plenum for circulation control. A shaft, which is driven from a transmission, drives a torque plate which is attached to the top of the hub member. A flexible hub plate is attached to a flange on the hub member and has a plurality of axles to which the rotor blades are individually attached. Air from inside the plenum is piped to the rotor blades through flexible ducts. The flexible hub plate is designed to provide a high degree of stiffness in the plane of rotation and a lesser degree of stiffness in a plane normal to the plane of rotation.

Abstract: A system of rotatably and pivotally mounted radially extended bent supports for radially extending windmill rotor vanes in combination with axially movable radially extended control struts connected to the vanes with semi-automatic and automatic torque and other sensing and servo units provide automatic adjustment of the windmill vanes relative to their axes of rotation to produce mechanical output at constant torque or at constant speed or electrical quantities dependent thereon.

Abstract: The present rotor head for a helicopter is free of flapping hinges and free of drag or lagging hinges. The rotor blades or wings are connected to the rotor head by a plurality of connecting plates which are flexible to bending moments. These plates are inserted into the blade roots of the helicopter wings and connected to the rotor head proper. The planes defined by these connecting plates intersect in the axis of the rotor blades or wings.

Abstract: A helicopter rotor having at least one blade projecting from the central hub and mounted for pitch change, flapping and lead-lag motion and including a lead-lag damper mounted to be pivotally movable in a selected plane and connected to the blade through a pivotal link connection to avoid the adverse effects of pitch and flap coupling.

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.