Patent ID: 8235665

Claim:
An aircraft comprising: a blade; a hub; a tension-torsion strap assembly coupling the blade to the hub, the tension-torsion strap assembly comprising: at least a first sculptured spool and at least a second sculptured spool, the first and second sculptured spools each comprising: a spindle having a first end and a second end; a first plate at a first end of the spindle and a second plate at a second end of the spindle, wherein an interior surface of the first plate proximate the first end of the spindle and an interior surface of the second plate proximate the second end of the spindle comprises a sloped contour wherein the sloped contour of the first plate or the second plate comprises a true radius between about 2 inches and 6 inches with an edge blend radius between about 0.02 inches to about 0.06 inches; and a strap wound around the first sculptured spool and the second sculptured spool, wherein the strap is formed from a material having a low torsional stiffness, and wherein the sloped contour reduces tensile and bearing stresses in portions of the strap adjacent the spool plates during articulation of the strap.