Sikorsky Aircraft Corporation

Douglas E Tritsch

David H Hunter

Francis E Byrnes

A monolithic structural member (10) operative for reacting steady and vibratory bending moment loads M about an applied loads axis X and having a specially configured cross-sectional configuration for providing improved flaw tolerance. The cross-sectional configuration (10) includes a central connecting element (18) and at least one pair of structural ribs (14a, 14b) being integrally formed with the central connecting element (18) and projecting outwardly thereof. The structural ribs (14a, 14b) are, furthermore disposed in the tensile field produced by the steady portion of the bending moment loads M and are proximal to the centroid C.sub.T of the cross-section (10). The cross-sectional configuration (10) defined by the structural ribs and connecting element produces a partial inertia ratio I.sub.X /I.sub.Y greater than or equal to 1.0, which partial inertia ratio I.sub.X /I.sub.Y has the advantageous effect of retarding or arresting crack propagation in the structural member (10). The cross-sectional configuration (10), as adapted for use in a helicopter rotor hub assembly (50), provides improved flaw tolerance and improved clearance between rotor hub assembly components. Specifically, the cross-sectional configuration (10) has a double-tee cross-sectional shape and is employed in areas corresponding to the midsection (64m) of each rotor assembly yoke (64) and shear segments (62) of the hub retention member (52). The double-tee cross-sectional configuration (10) facilitates higher flapwise and edgewise angular excursions between the yoke (64) and hub retention member (52) thus providing greater design flexibility and/or reducing the size and weight of the rotor hub assembly (50).

Monolithic structure having improved flaw tolerance

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. Bearing endplates (40) are bonded to the spherical elastomeric elements (34) and are mounted in combination with the yoke (24) and hub retention member (12). In operation, the central bearing element (32) is rotationally self-positioning to effect load and motion sharing between the spherical elastomeric elements (34).

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Beavercreek, OH, United States of America

Douglas E Tritsch