Abstract: A rotor for use in an aircraft includes an inner hub; and a plurality of blades arranged around the inner hub, each of the plurality of blades comprising an inner structural member; an outer blade shell surrounding the inner structural member; and a centering block located at a base of the inner structural member proximal to the inner hub, wherein the centering block is located between a first lateral portion of the inner structural member and a second lateral portion of the inner structural member, wherein the centering block is further connected to the outer blade shell, and wherein the centering block allows the outer blade shell to rotate about an axis approximately corresponding to the inner structural member.

Abstract: A rotor for use in an aircraft includes an inner hub; and a plurality of blades arranged around the inner hub, each of the plurality of blades comprising an inner structural member; an outer blade shell surrounding the inner structural member; and a centering block located at a base of the inner structural member proximal to the inner hub, wherein the centering block is located between a first lateral portion of the inner structural member and a second lateral portion of the inner structural member, wherein the centering block is further connected to the outer blade shell, and wherein the centering block allows the outer blade shell to rotate about an axis approximately corresponding to the inner structural member.

Abstract: A snubber inner member has a doubly convex outer surface portion having a central longitudinal axis. A shim/spacer stack secured to the outer surface portion couples the snubber inner member to the second member. A retainer having one or more engagement surfaces cooperates with one or more engagement surfaces of the snubber inner member to constrain lateral movement of the snubber inner member relative to the retainer while permitting longitudinal movement of the snubber inner member away from the retainer. An elastomer secures the retainer to the first member.

Abstract: A snubber inner member has a doubly convex outer surface portion having a central longitudinal axis. A shim/spacer stack secured to the outer surface portion couples the snubber inner member to the second member. A retainer having one or more engagement surfaces cooperates with one or more engagement surfaces of the snubber inner member to constrain lateral movement of the snubber inner member relative to the retainer while permitting longitudinal movement of the snubber inner member away from the retainer. An elastomer secures the retainer to the first member.

Abstract: A variable diameter rotor blade assembly includes a rotor hub with multiple rotor blades each having an outboard blade section telescopically mounted to an inboard blade section. A reeling assembly includes a strap drum that extends and retracts a strap attached to each of the outboard blade sections to selectively change the diameter of the rotor blade assembly. The strap includes a body portion extending toward the drum and a termination portion attached to each of the outboard blade sections. The termination portion is made from a rigid fiber reinforced composite that has a higher rigidity than the body portion. A transition region is formed between the body portion and the termination portion and is made from a flexible matrix-fiber composite that has a higher rigidity than the body portion and a lower rigidity than the rigid fiber reinforced composite.

Abstract: A variable diameter rotor blade assembly includes a rotor hub with multiple rotor blades each having an outboard blade section telescopically mounted to an inboard blade section. A reeling assembly includes a strap drum that extends and retracts a strap attached to each of the outboard blade sections to selectively change the diameter of the rotor blade assembly. The strap includes a body portion extending toward the drum and a termination portion attached to each of the outboard blade sections. The termination portion is made from a rigid fiber reinforced composite that has a higher rigidity than the body portion. A transition region is formed between the body portion and the termination portion and is made from a flexible matrix-fiber composite that has a higher rigidity than the body portion and a lower rigidity than the rigid fiber reinforced composite.

Abstract: A VDR blade lock system includes a set of blade pins that are rigidly mounted into the outboard blade section and a set of mount pins that are rigidly mounted to a rotor mount assembly. A resilient bushing at least partially surrounds each pin to provide high-energy absorption, impact resistance and low compressive modules. Should the outboard rotor blade section become free, centrifugal force will cause the outboard rotor blade section to rapidly telescope radially outward over the inboard blade section. The lock system prevents full extension of the outboard rotor blade section while the bushings act as a series of springs to reduce the deceleration rate of the outboard rotor blade section to minimize an impact force experienced by the VDR system.

Abstract: A novel apparatus and method are provided to reduce the interlaminar shear loading in the retention area of composite springs used in a vibration isolator for use with a helicopter main rotor. The composite springs, which are made of a graphite laminate, are weakest when subject to inter-laminate shear. The shear forces are highest during bending and twisting about the longitudinal axis of the laminate composite. The invention consists of several techniques to minimize the inter-laminate shear. The first is the use of nylon mounting pads which are attached to the ends of the graphite laminate spring arm at the locations where mounting to the inner and outer hubs is to take place. In particular, it has been found that the nylon spacer must be recessed back from the perimeter edges of the graphite spring arm the same distance which is approximately equal to the width of the graphite spring arm.

Abstract: A structural interlock (40) for inhibiting relative rotation between mating elements (20, 42) characterized by a plurality of grooves (50) being formed in one of the mating elements, and a mechanism (60) for producing a nominal contact pressure on the contact area (A.sub.1 thru A.sub.8) between the mating element, which contact pressure elastically deforms the other of the mating elements into the grooves (50), and is less than the material yield strength of either of the mating elements. In the preferred embodiment, the grooves (50) are radially oriented and an applied compressive load produces a nominal contact pressure which is about 80% of the material yield strength.

Abstract: An optimized composite flexbeam (10) having a pitch region (PR) which includes a core laminate (50) of unidirectional fiberglass material (U.sub.F), and face laminates (52) of unidirectional graphite material (U.sub.G) bonded to mating surfaces (50.sub.M) defined by the core laminate (50). The core laminate (50) and face laminates define an aspect ratio which is greater than or equal to 10 and define chamfered edge surfaces (54.sub.S). Each chamfered edge surface (54.sub.S) defines a critical acute angle .alpha. with respect to the flapwise bending neutral axis (X.sub.A) of the pitch region (PR) and defines a lateral edge (54.sub.E) disposed a vertical distance X from the flapwise bending neutral axis (X.sub.A). The critical acute angle .alpha. is between about 14 degrees to about 22 degrees and the vertical distance X is about 12.5% to about 37.5% of the pitch region thickness dimension (T.sub.PR).

Abstract: An axisymmetric elastomeric bearing assembly (30) for an articulated rotor hub assembly (10), which axisymmetric elastomeric bearing assembly (30) is disposed in combination with a rotor assembly yoke (24) and hub retention member (12) of the rotor hub assembly (10) and is operative for accommodating the multi-directional displacement of a rotor blade assembly (14) thereof. The axisymmetric elastomeric bearing assembly (30) includes a central bearing element (32) having a spherical bearing surface (32s) defining a bearing focal point (30f) and spherical elastomeric elements (34) bonded to the spherical bearing surface (32s) on opposing sides of the bearing focal point (30f). Each of the spherical elastomeric elements (34) have a plurality of alternating layers of elastomer and nonresilient shims (36, 38) which have a center of curvature which is coincident with the bearing focal point (30f) and disposed at increasing radii therefrom.

Abstract: An acoustic isolator is incorporated between a noise generating device and a support structure, such as between a transmission housing and an airframe. The isolator has a first fitting which attaches to the noise generating device, and a second fitting which attaches to the support structure, with an acoustic attenuation member disposed therebetween. Preferably, a first elastomer member is disposed between a pair of vertical walls of the first and second fittings. Optionally, a second elastomer member is disposed between an upper surface of the supporting structure and a lower surface of the second fitting such that horizontal loads are reacted therethrough. Alternatively the first and second elastomers comprise a spherical elastomer member and a cylindrical elastomer member in the form of a spherical bearing.

Abstract: A mounting assembly (100) is provided for securing a helicopter snubber bearing (70) to a bearingless rotor assembly (10) which includes a flexbeam connector (22) mounted to a torque drive hub member (18). The mounting assembly (100) includes a retainer fixture (102) for mounting a retainer (104) which engages an inner bearing race portion (88) of the snubber bearing (70). The retainer fixture (102) is mounted to the flexbeam connector (22) and includes an inboard end portion (112), a restraint portion (114) extending radially outboard thereof, and a seat portion (116) disposed therebetween. The retainer (104) is disposed in register with, and is compliantly bonded to, the seat portion (116) of the retainer fixture (102), and furthermore abuts the restraint portion (114) which provides redundant retention therefor.

Abstract: A pitch adjustment assembly (100) for a bearingless rotor assembly (20) which includes a torque tube member (36) enveloping a flexbeam connector (22), which torque tube member (36) defines a geometric center (120) and is operative to impart pitch motion to the rotor blade assembly (20).

Abstract: A tubular elastomer damper has a central shaft disposed within a housing and surrounded by an elastomer member. Uniform strain is provided across the elastomer disposed between the central shaft and the housing by either tapering the length of the elastomer from an inner to an outer bonding surface such that the radius times the length at each point along the elastomer is equal or by providing a first elastomer layer adjacent the shaft having a high fatigue strain/lower damping ability, a second elastomer layer adjacent the housing having a low strain higher damping ability and an intermediate elastomer layer of moderate strain and damping therebetween such that from the inner to the outer radius of the elastomer member, uniform strain is achieved. By providing uniform strain from the inner to the outer radius of the tubular elastomer damper, temperature increases due to localized high strains are avoided which are detrimental to damper performance.

Abstract: A hybrid composite flexbeam for a soft inplane bearingless main rotor assembly has eight spanwise regions: a hub attachment region; a first tapered region; a second tapered region; an inboard transition region; a pitch region having a cruciform configuration; an outboard transition region; a tapered outboard transition region; and a main rotor blade, torque tube attachment region. The pitch region is formed from unidirectional fiberglass plies, a 50/50 admixture of unidirectional fiberglass and graphite plies, and unidirectional graphite plies, all of which extend from root to tip of the hybrid flexbeam. Unidirectional fiberglass and graphite plies of varying lengths are interleaved in the second inboard tapered region. Fiberglass and graphite cross plies of varying lengths are interleaved in the first inboard tapered region. Fiberglass and graphite cross plies and unidirectional fiberglass plies of varying length are interleaved in the outboard tapered region.

Abstract: A flexbeam for a soft inplane bearingless main rotor assembly has six spanwise regions: a hub attachment region; a first tapered region; a second tapered region; a pitch region; a tapered outboard transition region; and a main rotor blade, torque tube attachment region. One described embodiment of the flexbeam is fabricated from continuous unidirectional fiberglass plies having a 0.degree. fiber orientation, unidirectional fiberglass plies of varying lengths having a 0.degree. fiber orientation, and graphite cross plies having .+-.45.degree. fiber orientations. The pitch region is formed solely by the continuous fiberglass plies which define a rectangular cross section therefor. The second tapered region is formed solely by the continuous fiberglass plies and the fiberglass plies of varying lengths. The ends of the fiberglass plies terminate in a distributed arrangement in the second tapered region to define the taper thereof.

Abstract: A flexbeam helicopter rotor having an improved connection between the flexbeam and the hub of the connecting pin variety but in which the high tensile fibers of the flexbeam do not wrap around the connecting pin, wherein the blade centrifugal loads and the blade lead-lag loads are reacted by the connecting pin at a station where it passes through drilled holes in the flexbeam inner end, and wherein the blade flapping motion imposed loads are reacted through two load paths in the flexbeam-to-hub connection, the first load path being created by a prying reaction between the flexbeam and the hub connecting flanges, and the second load path being created by the differential bending reaction between the flexbeam at the station of the drilled holes and the connecting bolts.

Abstract: A composite torque tube for a bearingless main rotor (BMR) assembly that is optimally fabricated to meet torsional stiffness, fatigue strength, and buckling strength design constraints at minimal unit weight. The composite torque tube includes a strengthened inboard section for mechanically coupling the torque tube in combination with the hub structure of the BMR assembly, a strengthened outboard section for mechanically coupling the torque tube in combination with a corresponding main rotor blade, and an intermediate section that is operative to accommodate the pitch, flapwise, and/or edgewise loads acting on the BMR assembly during operation thereof. The intermediate section of the torque tube has a constant wall thickness and is formed from continuous filament windings having a predetermined fiber orientation within a broad range of about +/-18.degree. to about +/-40.degree. and/or a narrow range of about +/-26.degree. to about +/-35.degree..

Abstract: A snubber set (30) for a helicopter rotor (10) is comprised of an inner race (44), an intermediate race (45), a preload plate (46), an inner portion (48) having alternating laminates of elastomer (52) and metal shims (54) which are spherically shaped, and an outer portion (50) having alternating laminates of elastomer (58) and metal shims (60) which are flat. The flat laminates (58) are comprised of a center portion (61) made from a high loss elastomer and a peripheral portion (62) made from a high shear strength elastomer.