normal plane rotation

how is the relationship between the rotation of the normal plane at each curve´s point and the geometry of the own curve?

i get the osculator plane (red in the image) and perpendicular to this plane the normal plane (magenta).

if i get the normal plane (green) to the curve using Pframes the plane  is the same plane obviously but is rotated in relation to the previous plane.

someone could help me?

thanks

normal_plane.gh