Rotor assembly with weathervaning sheath for blade roots

A rotor assembly 38 includes a hub 42 disposed for rotation about an axis of rotation 24. The rotor assembly also includes at least one blade 46 fixed with the hub for concurrent rotation with the hub. The at least one blade extends along a height axis radially outward from the hub with a root portion 66 proximate to the hub at a first end of the height axis and an airfoil portion 70 extending radially inward from a second end of the height axis opposite the first end. The rotor assembly also includes a sheath 76 extending at least partially around the root portion. The sheath is pivotally engaged with the at least one blade to pivot about the height axis and allowed to weathervane to reduce noise. The arrangement enables a more streamlined passage of exhaust gases passed the blade roots in a contra-rotating open rotor apparatus having pusher blades.