RotationReference defines the reference for the z-rotation it is either sparUID or„LeadingEdge“ or „TrailingEdge“. If it is not defined the rotation reference is the eta-axis (=leading edge, that is projected on the wings y-z-plane). A z-rotation angle of 90 degrees means, that the rib is perpendicular on the ribRotationReference (e.g. spar, leading edge...). The rib itself is allways straight, and the rotation is defined with respect of the intersection point of the rib with the ribRotationReference.

The rotation around z describes the rotation around the wings midplane normal axis. The defaults to 90°. The reference for the 'zero-angle' of the z-rotation is defined in ribRotationReference.