Abstract: A pitch change slide is mounted for longitudinal movement on a propeller shaft hub adapter in turn secured to the engine shaft of an aircraft engine, the said slide carrying a plurality of toothed racks each engaged with a spur gear on the base of one of a plurality of rotatably mounted propeller blades. Reciprocation of the pitch change slide changes the pitch of the propeller blades. The pitch change slide carries a coiled spring. A spring pressure slide, mounted for longitudinal movement on the propeller shaft hub adapter, has a flange bearing against the coiled spring, and is reciprocable on the propeller shaft hub adapter through a control rod operable from the aircraft cabin, thereby to adjust the degree of compression of the spring. Weights are mounted on the propeller blades and generate centrifugal force as the engine shaft turns, the said centrifugal force tending to rotate and change the pitch of the propeller blades.