Abstract: A major design consideration in helicopters is that of compensating for ssses on blades resulting from air forces during blade revolutions. Spinning rotor blades are severely stressed. To some degree conventional articulated helicopter rotor hubs overcome vibration difficulties, but high maintenance is a problem. Hingeless helicopter rotor assemblies, generally employing composite materials, were developed to overcome these obstacles. Such hingeless helicopter rotor assemblies usually include a rigid central hub member, and radial flexbeams rigidly attached to the hub member. Flexbeam rotors do not completely eliminate the dynamic instability difficulty. Even using these designs energy must be absorbed by damping means. The shear principle of damping is utilized in this invention.

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: 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: Links (48-50) tangential to the rotorshaft (30) and connected to the inner swashplate ring (38) center the swashplate and restrain it from rotating (in the case of a stationary inner ring) by attachment to gearbox lugs (34-36), or drive it in unison with the rotorshaft (in the case of a rotating inner ring) by attachment to rotorshaft flanges. Spherical (rod-end) bearings (52-54, 56-58) so that the links can accommodate collective and cyclic swashplate attitude changes by moving out of plane.Links (70-72) tangential to the outer swashplate ring (64) and connected thereto and to the airframe (74) perform a similar function in restraining, centering and allowing for collective/cyclic movement of a stationary outer swashplate ring.

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 threadless retention apparatus holds a spindle (2) against a bearing (22) in a helicopter hub and has a split ring (10) mating with an annular spindle groove (4) and a loading hoop (32) holding the ring (10) within the groove (4), the loading hoop (32) locating the ring (10) and spindle (2) in relation to the bearing (10) as a unit.

Abstract: Apparatus for damping blade lead/lag motion on a hingeless helicopter rotor assembly, including a hub, blades and flexbeam(s) interposed between the root end of the blades and the hub. Rigid, radial links extend the length of the flexbeams for attachment to the outboard ends thereof. Lead/lag motion at the outboard end of the flexbeam causes flexbeam bending, which is converted to radial translation of the links. This radial translation of the links and likewise the blade lead/lag motion is damped by damper means connected between the inboard ends of the links and the hub.

Abstract: Centering and stabilizing against rotation of a helicopter swashplate stationary ring are provided by spokes that are attached between the airframe and the stationary ring. When the swashplate tilts for cyclic control, the spokes bend and twist. When the swashplate translates for collective control, the spokes are required to lengthen and skew with respect to the swashplate. An elastomeric bearing having a cylindrical component to allow for skew and a shear pad to allow for lengthening attaches each spoke to the swashplate. The invention eliminates the need for the ball joint, standpipe and scissors associated with traditional swashplate centering techniques.

Abstract: The axial load-carrying ability of an axially-lobed, nearly-spherical elastomeric joint is enhanced by offsetting the elastomer layers so that there is more elastomer to react the load in compression. The improvement is useful in the application of the joint to a gimbal-like rotor system.

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 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: 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: 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: 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 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: 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 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: 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.