Abstract: An improved clevis joint capable of withstanding substantial pivotal motion between its joined members and loading along its axis. An improved clevis joint wherein the parts joined thereby are pivotally connected by two sets of elastomeric bearings which are free to rotate about the joint axis and which envelope and support a free floating centering pin from the joined members so that during motion between the joined members, said elastomeric bearing sets share the rotary motion due to the rotating of the connecting pin.

Abstract: An articulated helicopter rotor wherein the blade-to-hub connection consists of a spherical elastomeric bearing connected to the hub and a composite yoke connected thereto in series and consisting of a plurality of unidirectional high strength fibers bonded together to form a continuous strap which passes through a central opening in the elastomeric bearing and is pin-wrap connected to the hub at a single station and to the blade at two spaced stations produces a construction which is light in weight, easy to manufacture, ballistrically tolerant, redundant, and readily visually inspectable for structural integrity.

Abstract: A flexbeam 16 for a bearingless helicoptor rotor includes a composite beam 28, composed of unidirectional fibers bound in an epoxy matrix, having ribs 32, composed of unidirectional fibers bound in a urethane matrix, bonded to each horizontal face at the section of the beam 28 which accommodates lead-lag torsion.

Abstract: A flexbeam helicopter rotor having an improved snubber-vibration damper for positioning the flexbeam spar relative to the torque tube, wherein the snubber-damper is an elastomeric bearing having a spherical and a flat portion, and whose laminates are continuous, selectively preloaded and of selected material to provide increased fatigue life, size reduction, reduced laminate stress concentration, and reduced critical design stress in the snubber-vibration damper.

Abstract: A swashplate configuration for helicopter which eliminates the need for scissors linkages through the use of a centering member capable of tilt and axial translation while driving torque to the rotating swashplate member through the use of elastomeric bearing assemblies each consisting of a first stack of flat laminates and a second stack of spherical laminates.

Abstract: A pitch retention member has a mounting surface which receives an elastomeric bearing disposed within a coupling attaching to the root end of the propeller blade. The mounting surface of the pitch retention member is conical. The coupling has a conically shaped bearing mounted therein which is bolted to the root end of the propeller blade. By bolding the coupling to the spar the conically shaped elastomeric bearing is precompressed against the conical mounting surface.

Abstract: A hybrid metal composite rotor hub retention plate having high strength and reduced weight. The retention plate comprises a metallic perimeter support structure and a plurality of metallic spokes that extend inwardly from the perimeter structure to a hub. The perimeter structure, hub and spokes define at least three holes. The perimeter structure and spokes have upper and lower surfaces. Fiber reinforced resin matrix composite capable of reacting to bending loads, in-plane shear and axial loads is bonded to the upper and lower surfaces. The hybrid metal composite rotor hub retention plate is made by forming the metal structure and using the metal structure as a mold for the fiber reinforced resin matrix composite.

Abstract: A hollow spherical or conical elastomeric bearing has an elliptical inner surface whose minor diameter is aligned with the resultant nonaxial load under a compressive axial load.

Abstract: A helicopter composite swashplate ring that has a triaxial braided tubular ring that withstands both forces in-plane and normal to the plane of the swashplate. The triaxial braided tubular ring comprises substantially circumferential fibers interwoven with angled fibers oriented at a predetermined angle to the circumferential fibers. The tubular ring contains a composite circumferential spacer ring that comprises an upper ring plate connected to a lower ring plate by a plurality of first tubular support members. The upper ring plate and lower ring plate are adjacent the inside upper and insider lower surfaces of the tubular ring, respectively. The upper and lower plates have openings in alignment with the first tubular support members. The ring plates have a plurality of sections extending radially outward. The sections have lug openings that are in alignment with a plurality of second vertical support members to form channels therethrough for accepting servo or control rod lugs.

Abstract: A fiber reinforced braided composite main helicopter rotor hub retention plate whose fiber orientation withstands forces both in the plane of the retention plate and normal to the plane. The retention plate comprises a fiber reinforced resin braided tubular ring having substantially circumferential fibers interwoven with angled fibers disposed about a central core. Arms extend inward from the braided ring for attachment to a driveshaft.

Abstract: The lag-torsion flexure portion (16) of a flexbeam (10) having segregated lag-torsion flexure portions (16) and flap flexure portions has multiple longitudinal lobes (98A-98G, 100A-100G) formed by multiple grooves (90A-90F, 92A-92F) extending from the upper (94) and lower (96) surfaces of the lag-torsion flexure portion to a central planar portion (102) thereof. The bases of the grooves are radiused (r) for favorable stress distribution while allowing for torsional and lead/lag softness in the lag-torsion flexure portion. The preferred number of grooves is an even number, such as six, resulting in an odd number of lobes. The lobes may decrease in height from the central lobe to the edgemost lobes (FIG. 12A). The lobes may be radiused at the upper and lower surfaces of the lag-torsion flexure portions (FIG. 12B). The lobes may be formed of alternate layers of unidirectional longitudinal fiber (32) extending the length of the flexbeam and elastomeric material (112) (FIG. 12D).

Abstract: A nearly spherical laminated elastomeric bearing has a non-circular latitudinal cross-section to accommodate high torque loads in elastomer bending rather than in shear. The nearly spherical profile of the bearing accommodates tilt primarily in shear. Both inwardly and outwardly extending lobes, or splines, are disclosed. The nearly spherical, lobed bearing is useful for a constant velocity joint.

Abstract: The tiltwise stiffness of an axially-lobed, nearly-spherical elastomeric joint is made uniform at all azimuths by contouring the axial height of the elastomer or by reducing the thickness or durometer of the elastomer at azimuths where the joint otherwise would be tiltwise stiffer, such as at the lobes. The improvement is useful in the application of the joint to a gimbal-like rotor system.

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: 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 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.