A pitch change mechanism for a bladed rotor includes a driving sleeve, a drive shaft, a first pitch-changing element, a second pitch-changing element, and a plurality of blade drive gears. The driving sleeve has, in axial sequence, a first helical connection portion and a second helical connection portion. The driving sleeve is positioned concentrically with and surrounding the drive shaft. The first pitch-changing element has a first end drivingly engaged with the first helical connection portion, and a first ring gear portion at a second opposite end, while the second pitch-changing element has a first end drivingly engaged with the second helical connection portion, and a second ring gear portion at a second opposite end. The plurality of blade drive gears are arranged in a circumferential array around a longitudinal axis of the drive shaft.