A speed reducer, particularly of an aircraft, includes a central sun gear mounted to rotate with a drive shaft about a rotation axis X, an annular ring gear coaxial with the X axis, and a plurality of planet gears arranged about the X axis and mounted to be movable on a planet carrier. The planet gears engages the sun gear and the annular ring gear, which extends around the planet gears. The speed reducer further includes a lubricant recovery device having a pipe for recovering lubricant discharged from the reducer by centrifuging. The recovery device has scoops mounted to pivot about a pivot axis P on a movable member of the speed reducer that rotates about the X axis between a deployed state and a rest state.