A reduction gear box is part of a gas turbine engine and includes a casing and reduction epicyclic gear stages within the casing. The reduction gear stages comprising at least an epicyclic array of gears meshing together with at least one planetary gear mounted for rotation on a gear carrier and a bearing associated therewith. A lubricating oil delivery system is provided within the casing, surrounding a portion of the gear carrier. The oil delivery system includes a conduit; a closed oil reservoir; a first metered opening communicating the conduit with the reservoir and a plurality of metered outlet openings communicating the reservoir with the gear carrier and the bearing such that the reservoir is filled with oil in normal flight operating conditions and the oil trapped in the reservoir is released to the carrier and bearing when a temporary drop in the oil system pressure occurs.