Abstract: Hub moment and driving torque is provided for a helicopter gimbal rotor by two-part flat springs that are in-plane with the rotor tilt point (P). The inboard end of an outward part of each spring is connected to the rotorshaft and the inboard end of an inward part of the spring is connected to the tiltable hub member. The outboard ends of the two spring parts are journaled together by an eccentric elastomeric joint that allows for spring foreshortening that accompanies rotor tilt.

Abstract: A helicopter hub main retention plate is described made up of graphite and glass fiber reinforced epoxy resin. The graphite fiber reinforcement is in-plane isotropically laid continuous graphite fibers and the glass fiber reinforcement comprises segments of fiberglass continuously and circumferentially wound around the areas of retention. Such materials and configuration provide crack resistance, damage tolerance, and integrity inspectability to the retention plate.

Abstract: A composite torque tube for a helicopter rotor hub is described. The torque tube contains upper and lower load bearing surfaces connected by two sidewall portions. Both the sidewall and load bearing portions contain filament wound glass fiber reinforced epoxy resin such fibers having a .+-.45.degree. orientation. The upper and lower load bearing portions additionally contain a plurality of multiaxially oriented plies of continuous unidirectionally oriented graphite fibers interleaved with the glass fibers so as to produce a torque tube with crack resistance, damage tolerance, light weight, strength and integrity inspectability.

Abstract: A composite helicopter rotor hub is described having a composite retention plate, yokes and torque tubes. The retention plate is made up of graphite and glass fiber reinforced epoxy resin. The graphite fiber reinforcement is in-plane isotropically laid continuous graphite fibers and the glass fiber reinforcement comprises segments of fiberglass continuously and circumferentially wound around the areas of retention. The yoke is made up of glass fibers unidirectionally oriented in the direction of principle stress, i.e., along the length of the yoke. The yoke also has clevis sections on either end and the clevis sections additionally contain multiaxially oriented multiple plies of unidirectionally oriented continuous graphite fibers interleaved with the unidirectionally oriented continuous glass fibers. The torque tube contains upper and lower load bearing surfaces connected by two sidewall portions.

Abstract: Hub moment for a tilt rotor is provided by U-shaped springs that extend outwardly from the rotorshaft and in-plane with the tilt point (P) and inwardly to the tiltable hub member in the rotor plane, which is above the tilt point (P). Driving torque is supplied to the rotor via a torque disc that has a resilient diaphragm portion attached to the rotorshaft in-plane with the tilt point (P) and a rigid rim attached to the tiltable hub member in the rotor plane. The torque disc comprises the lower half of an aerodynamic fairing which encases the hub.

Abstract: The device comprises two rigid elements 1a, 1b, 2 and an elastomer mass 10 interposed therebetween so as to be deformed when the elements move relative to each other in a longitudinal direction. The device includes a closed space with a restriction element 16 defining two chambers 23, 24 whose volumes vary inversely upon movement of the chamber walls, the two chambers being interconnected by one or more passages, the empty space being filled with a viscous fluid material so as to produce a damping effect in the passages. Application to helicopter blade frequency adapters.

Abstract: A hub plate and helicopter rotor incorporating same made of a composite material and comprising a laminated disc constituted by layers of fiber cloth having high mechanical strength. A frame of the disc is made of aligned layers of the cloth with the weft or warp of the cloth extending radially in the direction corresponding to the direction of centrifugal force acting on the plate when in use. The aligned layers are positioned at the core of the structure and at least at the surface of the structure in the peripheral portion of the disc. The disc is enclosed by a belt of parallel threads consisting of fibers having high mechanical strength fitted on radially outwardly projecting parts of the disc in recesses formed in the outer edge of the parts, the recesses being open to the exterior.

Abstract: Helicopter rotor on which the blades are each connected to a center hub plate by means of a U-shaped fork connected to the hub by an elastomer support, the latter supporting a static supporting device for limiting dynamic oscillation on the relative blade in the vertical plane, the said device providing for use of a pin faceted on the side, mounted so as to turn on a taper seat integral with the relative fork and designed to engage with a mating surface integral with the hub.

Abstract: A bearingless helicopter rotor includes an integral damper and pitch change assembly (16) adapted to damp lead/lag movements of a rotor blade and to change the pitch of the rotor blade. In described embodiments, the assembly includes a generally tubular body portion (17, 27) closed at one end and attached by torque transmitting means (18, 28) to a flexure member blade attachment and a rod (20, 29) protruding axially from the other end of the body portion and attached adjacent the rotor hub. Pitch change movements are effected by rotation of the body portion about its longitudinal axis and damping of lead/lag movements either by metering of an incompressible medium across a piston (23) in a chamber (24) formed internally of the body portion or by an annular body of elastomer material (34) bonded to the outside diameter of the rod and the inside diameter of the body portion.

Abstract: A flexible blade neck of a helicopter rotor blade is bridged by a torsion gid sleeve for the blade angle adjustments. The radially outer end of the blade neck and sleeve are rigidly connected to the wing section of the blade. The radially inner end of the blade neck forms a blade root which is secure to the rotor head or hub. Additionally, the radially inner ends of the blade root and of the sleeve are interconnected by a ball and socket arrangement permitting a universal movement between the sleeve and the blade neck, thereby decoupling sleeve movements from the blade neck and vice versa.

Abstract: The blade angle of the blades is adjustable in a rotor for a rotary wing craft by a lever mechanism (13, 14 or 41, 42) secured to the radially inner end of an extension bushing (7; 7.1) or shaft (43). The extension bushing (7; 7.1) or shaft (43) is connected with its radially outer lever (15 or 44) to the blade root (2) or a blade root mounting (39, 50) of a rotor blade in an angular position adjustable manner for adjusting the tracking of the blades. The bushing (7; 7.1) or shaft (43) is adjustable in its angular position relative to the blade root (2) by adjustment screws cooperating with a free end of the lever (15 or 44) which reaches into a gap between two of such adjustment screws (16 or 45) cooperating with counter nuts (17 or 46). By adjusting the angular position of the bushing or shaft with the screws it is possible to assure a uniform tracking among all the blades of a multiblade rotor. Such uniform tracking is desirable if the blades of a rotor are to rotate in the same plane.

Abstract: A rotor hub system for a helicopter in which the rotor hub and pitch housing are fabricated predominately of composite material, the flap hinge, pitch hinge and lead-lag hinge contain elastomeric bearings and one step blade folding in either the forward or aft direction using the same drive system. The rotor hub includes closed loop straps which define generally opposed lugs of the flap hinge, and the pitch housing includes a pair of closed loop straps which define the lugs of the lead-lag hinge and a lug of the flap hinge. The use of composite materials as the predominant material of the rotor hub and the pitch housing results in a highly load redundant structure permitting a reduction in size and number of parts, a reduction in drag, and an increase in reliability and safety.

Abstract: A rotor hub system for a helicopter in which the rotor hub and pitch housing are fabricated predominately of composite material, the flap hinge, pitch hinge and lead-lag hinge contain elastomeric bearings and one step blade folding in either the forward or aft direction using the same drive system. The rotor hub includes closed loop straps which define generally opposed lugs of the flap hinge, and the pitch housing includes a pair of closed loop straps which define the lugs of the lead-lag hinge and a lug of the flap hinge. The use of composite materials as the predominant material of the rotor hub and the pitch housing results in a highly load redundant structure permitting a reduction in size and number of parts, a reduction in drag, and an increase in reliability and safety.

Abstract: Helicopter rotor on which static balancing of the rotor is provided for by a number of annular-shaped counterweights housed inside each pin securing each blade to the hub; the said counterweights being supported by a rod pressed an clicked inside an axial hole on the relative pin.

Abstract: This invention relates to a system for mounting a helicopter rotor on a flapping axis and, more particularly, to use of an improved unitary trunnion-bearing structure of minimal parts which may be selectively preloaded and which is readily installed.

Abstract: A helicopter rotor hub having a lobed shape defining a plurality of bridge structures each allowing the attachment of a respective blade; each bridge structure is formed of superimposed sections of three annular bands, of synthetic material, the intermediate one of which forms an outer frame extending around the whole of the periphery of the hub, while the other two define one of the said lobes and connect the said outer frame to an inner metal structure.

Abstract: A structural element capable of resilient twisting about an axis including a plurality of axially extending open section members of decreasing transverse dimension nested together with adjacent ends of the members being rigidly interconnected at each end of the element.

Abstract: A helicopter rotor in which a central plate-like hub is provided with a plurality of axial apertures uniformly distributed around a central axis of rotation and each defined radially outwardly by a supporting peripheral bridge connected to a respective blade by a U-shape structure extending through the said aperture and coupled to the associated bridge by an elastomeric coupling; each U-shape structure being coupled to a respective radial projection of the hub by a further elastomeric coupling.

Abstract: FH (FLEX-HUB) helicopter rotor on which each blade is connected to a center hub by a fork having two arms on one side for connection to the relative blade and integral, on the other, to a rod connected to the hub by an elastomer support; the forks being interconnected by a polygonal ring passing between the said arms on each fork and each side of the said ring being supported centrally by a flexible arm extending radially from the hub.

Abstract: The invention concerns a helicopter rotor, the rigid hub (1) of which comprises a central drum (2) which is disposed substantially in line with the rotor mast (3) and which carries an upper plate (4) and a lower plate (6). This rigid hub (1) is connected to the root of each blade (26) by way of a laminated spherical stop (13) and a resilient-return drag brace. Each blade (26) comprises, in the zone of its root, a rigid loop (27) which surrounds the laminated spherical stop (13) in a continuous manner and is engaged in the inner movable fitting (24) of this stop (13) by means of a wedge (30) co-operating with the outer fixed fitting (15) of the stop (13).

Abstract: This invention is directed to helicopter rotor hubs which includes an elastomeric material between an inner and outer hub. The inclusion of elastomeric material transmits torque, thrust and in-plane loads and is flexible in the tilt direction.

Abstract: A countertorque rotor for helicopters in which a transmission shaft keyed transversely onto a drive shaft and disposed obliquely within a hub has each of its ends coupled in a slidable manner within an inner bush of an associated elastomeric coupling this latter carrying screw actuator means which can act axially on the said shaft to displace the said hub with respect to the shaft (3) itself in the direction of the axis of this latter.

Abstract: A helicopter rotor system using composite flexbeams for connecting a rotor blade to the rotor hub, each flexbeam being of C-section and having a web section made up of 0.degree. and .+-.45.degree. plies and top and bottom flanges made up of low angle plies in the direction of their length with their ends being connected by an arc of plies so that the top and bottom flange plies are continuous with an attachment fitting encased at the ends of the flexbeams.

Abstract: An aerodynamic rotor having a flexible blade comprising a plurality of planar layers and an anvil having configured bearing areas engagable with the flexed blade is presented. The plurality of layers are slidably movable in a shearing motion with respect to other layers. The blade is secured by the anvil with the configured bearing areas being engagable with an adjacent portion of the blade when the blade is flexed by forces created by the driven rotory motion of the anvil about an axis of rotation. Such a rotor with a laminated blade exhibits reduced head moment forces and reduced stress/strain forces within the blade thereby permitting improved reliability and maintenance.

Abstract: A connecting element having end regions (22, 23) joined by an intermediate by an intermediate region (26) is constructed of a plurality of fibre filaments extending longitudinally and continuously throughout its length. The fibers in the end regions are embedded in a thermo-setting resin matrix material and the fibres in the intermediate region are embedded in a resilient matrix material thereby permitting relative resilient torsional movement of the end regions about a longitudinal axis. Such a connecting element is particularly suited for use in a helicopter rotor and several embodiments are described and illustrated. In all embodiments the torsional flexibility of intermediate region (26) provides for blade feathering movements and in a preferred embodiment the inner end region (22) is constructed so as to be resiliently flexible in a blade flap plane and the outer end region (23) is constructed so as to be equally resiliently flexible in the blade flap and lead/lag planes.

Abstract: The blades or wings of a rotor for example of a rotary wing aircraft, are nnected to the rotor head in a hingeless and bearingless manner by a blade neck section, which is flexible relative to torsion loads, flapping movements and lead-lag movements. The blade angle adjustments are made by a torsion stiff control rod bridging the flexible blade neck section. The control rod is flexible relative to flapping and lead-lag movements. The radially outer end of the control rod is rigidly connected to the respective wing. The radially inner end of the control rod is connected to the rotor head in such a manner that the control rod is movable substantially in the direction of its own longitudinal axis.

Abstract: A helicopter rotor blade to hub arm attachment configured to react centrifugal loads from the blade through a blade cuff, spindle, and elastomeric bearings utilizes a bolt in the bore of the spindle for secondary load path operation and a spindle integrity monitoring indicator to provide a visual showing of a deviation from the normal load path.

Abstract: The blade angle of the blades of a rotary wing aircraft is adjusted by a control rod (5) inside the hollow rotor head operating a control shaft (8) extending radially out of the rotor head in axial alignment with the blade angle adjustment axis. The adjustment movement of the shaft (8) is transmitted to the respective blade (3.3) by a yoke (11, 12) and a torsion-stiff sleeve (7) which bridge the blade root (3.1) and the torsion yielding blade neck (3.2) respectively. The blade root (3.1) is connected to the rotor hub (1) by a forked member (2) through which a portion (11) of the yoke extends for connection to the control shaft.

Abstract: This invention relates to helicopter rotors and more particularly to rotor mounting involving a composite fiber-reinforced unitary yoke with resilient inplane restraints.

Abstract: A composite hub for a helicopter rotor, the hub having the form of a flat plate of laminated structure provided with a plurality of through holes each able to house an elastomeric coupling for connection of an associated blade, and a central layer of the said plate being constituted by a force distributor element in contact with each surface of which there is disposed at least one layer constituted by radial elements extending outwardly of an axis of rotation of the hub and an annular element disposed in contact with the free ends of the said radial elements; these latter being connected to the radial elements disposed on the other side of the distributor element by means of axial elements (25) defining part of the surface of the said aperture.

Abstract: A marine propeller includes a hub and a plurality of replaceable, respectively adjacently positioned blade support sections attached to the hub. The hub has a central portion and a plurality of spoke members that extend radially out from the central portion. Each of the blade support sections includes an inner lip that engages a respective one of the spoke members and an outer lip adjoining and overlapping the inner lip of an adjacent blade support section. Each pair of adjoining outer and inner lips are drawn tightly against a respective one of the spoke members by a plurality of screws. The spaces between the respective spoke members form a plurality of exhaust gas passages.

Abstract: A bearing assembly of concentric, cylindrical or conic rigid layers alternated with and bonded to elastomeric layers is bonded to a rigid, inner ring. A protective outer ring surrounds the bearing assembly and is equipped with devices for compressing the elastomeric layers to prevent bond failure between the layers when the assembly is subjected to radial loads. Bond failure is especially likely in bearings of this type because of tensile stresses built into the elastomer as a result of its tendency to shrink during its cure process. The bearing assemblies are conic in form, so that the elastomeric layers can be compressed by axial displacement of the rigid layers when the inner and outer rings are drawn together axially.

Abstract: A fiberglass-epoxy flexbeam extends from tip to tip of each opposed blade pair, carrying the blade centrifugal forces so that none of the centrifugal loading is carried by the hub. The primary load-carrying connector between the flexbeam and the hub is a set of elastomeric pads. These provide a soft mount between the flexbeam and the hub to keep the primary bending moments within the flexbeams where the filaments are designed to accommodate them. The elastomeric pads are also effective in isolating the hub from chordwise loads which include the steady driving torque and the "C" mode and "S" modes of coriolis vibration. The elastomeric hub mount damps these vibrations and tunes their frequencies to values well separated from the rotor frequency.

Abstract: A helicopter rotor blade to hub arm attachment configured to react centrifugal loads from the blade through a blade cuff, spindle, and elastomeric bearings utilizes a pre-loaded bolt through the spindle for load sharing therewith and a spindle integrity monitoring indicator to provide a visual showing of a deviation from the normal load sharing proportion.

Abstract: The wings of a hingeless helicopter rotor are secured to the head of the rotor by connecting elements of fiber compound materials. Each connecting element has at least two outer layers of fiber compound materials and an intermediate layer of .+-..beta.-fiber compound materials between the outer layers. The intermediate layer is bonded to the outer layers by a suitable adhesive. The intermediate layer takes up the central portion of the securing flange of the rotor head and its axial thickness increases radially inwardly. The intermediate layer has four side lobes which extend laterally out of the confines of the outer layers. These side lobes are connected by bolts to the rotor head. This structure provides a strong connection in which the outer layers are not weakened. Effects of the lead-lag movement of the rotor wings and of any torsion of the connecting elements are minimized and the fictitious hinges are located close to the rotational axis even within the zone defined by the rotor head flange.

Abstract: A helicopter rotor comprising elastomer joints, in which each blade is connected to a rotatable hub by means of a yoke constituted by a single U-shaped piece and mounted through a relative aperture provided in said hub;each yoke being connected to a transverse arm outwardly bordering said aperture, by means of a U stirrupembracing the relative said arm and provided with two overlying appendices extending outwards and having two surfaces inclined towards the other and acting as stop surfaces for two rocker arms constituting a devicefor controlling the flapping movements of said blade; said two rocker arms being mounted rotatable in a substantially vertical plane passing through the axis of the relative blade and being supported by a lever for controlling the pitch of this latter.

Abstract: An improved droop stop for a fully articulated helicopter rotor is provided herein curved mating surfaces are employed between the spindle pad and the centrifugal droop stop static support arm to provide surface rather than line contact therebetween during centrifugal operation. The centers of the curved surfaces are coincident at the pivot point of the droop stop centrifugal arm to force the downward load of the blade to pass through this pivot point.

Abstract: An elastomeric bearing assembly for supporting a rotor blade of a helicopter including a spherical elastomeric section mounted in serial relationship to a pair of frusto-conical elastomeric bearing section on the blade shaft. The frusto-conical bearing section includes two elastomeric bearings having bonded and alternate layers of elastomeric and non-extensible material and are arranged to receive the resulting force vectors in a direction normal to their planar surfaces.

Abstract: The invention relates to a rotary-wing aircraft rotor.The rotor comprises a hub 1 connected to each blade 7a by a rigid yoke 8-9 gripping the root of blade 7a and a spherical abutment 17 secured at its center C to radial arms 5a, 6a of hub 1 and bearing on its convex side against the inner end of yoke 8-9. According to the invention, an annular visco-elastic shock-absorber 20, constituting a frequency-matching device, is disposed between the yoke 8-9 associated with each blade 7a and the corresponding pitch control device 24-29.The invention is of use inter alia in the manufacture of fast helicopter rotors having a hub which is very compact and can therefore be easily streamlined.

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: 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 connecting element for securing a rotor blade to the rotor hub of a helicopter rotor comprises at least two components arranged at an angle relative to each other. At least one component extends outside the boundary of the other component on both sides of the other component. Slots are arranged in at least one of the components and these slots extend substantially toward the shearing center or rather toward the central shearing axis. Additionally, each connecting element has a flattened zone adjacent to the rotor hub to function as a flapping hinge. The connecting element also functions as a lead-lag hinge and as a torsion hinge.

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 bearing for carrying compressive radial loads comprising alternating bonded layers of a resilient material of a uniform modulus of elasticity and layers of a non-extensible material, all generally concentrically formed about a common center axis. The fatigue life of the bearing under torsional and compressive loads is enhanced by progressively decreasing both the length and thickness of each layer of resilient material with increasing radii, so that a substantially equal strain is carried across each layer of resilient material in response to each torsional load and the shape factor of each of the layers of resilient material remains substantially constant or increases with increasing radii.

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: 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: 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: An end closure for honeycomb structures is disclosed. The end closure effectively provides for the sealing of the end of a honeycomb structure in order to prevent moisture from entering and propagating into the structure. The invention includes a structure and method for closing the end of a honeycomb structure with a molded closure. A foam adhesive, in combination with a tape adhesive, forces the tape adhesive to conform to the shape of the irregular honeycomb core, thereby providing an effective bond and seal of the honeycomb face.

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.