Abstract: A coil spring (50) for use in an overrunning spring clutch assembly having a central arbor (16) for centering and supporting the coil spring (50) in an overrunning operating mode. The coil spring (50) includes teaser coils (52) disposed at each end thereof, central coils (54) disposed intermediate the teaser coils (52), and transition coils (56) disposed between and adjoining the teaser coils (52) and the central coils (54). The coil spring (50) is characterized by each of the transition coils (56) having an interface surface (56.sub.IS) being substantially complementary to a corresponding external bearing surface (16.sub.ES) defined by the central arbor (16) of the spring clutch assembly. Such substantially complementary relationship limits the radial deflection of the transition coils (56) in the overrunning operating mode, thereby reducing vibratory bending stresses in the coil spring (50).

Abstract: A mid-beam jointed reconfigurable bearingless main rotor (BMR) assembly that includes reconfiguration joints that facilitate BMR assembly reconfiguration by main rotor blade removal or folding to reduce the structural envelope of a helicopter for rapid deployment, routine transport, and/or storage. The BMR assembly comprises a rotor hub structure that includes a plurality of radially extending flexbeams, combinations of torsion flexure members and main rotor blades disposed in combination with corresponding flexbeams, and torque tube subassemblies disposed in combination with corresponding flexbeams and torsion flexure member, main rotor blade combinations. Each reconfiguration joint is formed by a combination of an outboard joint segment of a flexbeam and an inboard joint segment of the corresponding torsion flexure member.

Abstract: A retractable helicopter rotor in which the rotor and its blades, the swashplate and the pitch change rods are retracted and extended as a unit during the helicopter rotor retraction/extension mode of operation, wherein the connection between the rotor support system and the fuselage constitutes a single interface between overlapping circumferentially extending flanges of each, and with the bolts joining those flanges being loaded in compression.

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: An external composite wrap (34) of composite fibers (36) is added to the flap flexure portion (14) of a flexbeam (10), which is composed of predominantly unidirectional fibers (32) extending along the length of the flexbeam in (vertically) stacked layers (31). The fibers of the external wrap are disposed at an angle to the unidirectional ply fibers. The external wrap serves to reduce the interlaminar shear stresses in the unidirectional plies and increase the torsional stiffness of the flap flexure portion without significantly increasing the flexural stiffness of the flexbeam. The latter is accomplished by tailoring the thickness of the external wrap relative to flexbeam station (longitudinal position) and optimizing the angle of the external wrap fibers.

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: 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: 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.