An actuator arrangement includes epicyclic gearing having compound planetary gears each of whose pinions respectively mesh with a ring gear on a relatively fixed body and with two output ring gears to drive the latter in opposite directions relative to the body. The pinions which mesh with the ring gear on the body are free to rotate with respect to the remaining pinions and also mesh with a sun gear which is separate from, but driven by, the sun gear which drives the remaining pinions. The arrangement permits the gearing to overcome dimensional restraints imposed by prior art systems.