The rotor assembly can have a first disc having a first body extending circumferentially and radially around the axis, a first set of circumferentially distributed blades protruding radially from the first disc, and a male spline extending axially relative the first body, the male spline extending around and along the axis, and a second disc having a second body extending circumferentially and radially around the axis, a second set of circumferentially distributed blades protruding radially from the second disc, and a female spline extending around and along the axis, the female spline receiving the male spline in a spline engagement.