Sikorsky Aircraft Corporation

W Donald Jepson

David G Matuska

Edward W Gronenthal

A torque tube/spar assembly (100) for transferring operational loads of a Variable Diameter Rotor blade assembly (16) to a rotor hub assembly (18) and includes a torque tube member (24), a spar member (30) and a bearing assembly (40a, 40b) for telescopically mounting the spar member (30) to the torque tube member (24) and furthermore defines an internal channel (62) for housing a retraction/extension mechanism (64) which mounts to an internally formed restraint surface (86) of the spar member (30) and is operative to vary the length of the rotor blade assembly (18). The torque tube member (30) has a substantially constant external geometry along the length of bearing assembly engagement and defines a root end region (102), a tip end region (106) and an intermediate transition region (104) disposed therebetween. The spar member (30) has a substantially constant internal geometry and defines a root end region (110), a first transition (112), an intermediate region (114), a second transition region (116), a restraint region (118) and a tip end region (120). Each of the various regions of the torque tube and spar members (24, 30) have a characteristic stiffness value wherein the characteristic values (104m, 106m) of the intermediate transition and tip end regions (104,106) of the torque tube member (24) are less than the characteristic stiffness value (102m) of the root end region (102) thereof, and wherein the characteristic stiffness value (118m) of the restraint region (118) of the spar member (30) is greater than said characteristic stiffness values (114m, 120m) of the intermediate and tip end regions (114, 120) thereof, and wherein the characteristic stiffness value (114m) of the intermediate region (114) is less than the characteristic stiffness values (110m, 112m, 116m, 118m) of the root end, first transition, second transition and restraint regions (110, 112, 116, 118).

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Huntington, CT, United States of America

W Donald Jepson