Lubrication oil system for a reduction gearbox

An oil supply system for a reduction gearbox in a gas turbine engine, the reduction gearbox of the type having at least one reduction epicyclic gear stage, within the casing, the reduction gear stage comprising at least an array of gears meshing together with at least one gear mounted for rotation on a gear carrier and a bearing associated therewith, the engine being subject to normal flight and negative “g” flight conditions;

• the oil supply system comprising an oil reserve system consisting of a closed reservoir provided adjacent the gear carrier, a restricted inlet opening associated with the reservoir for allowing oil to enter and fill the reservoir in normal flight conditions and a plurality of metered outlet openings to feed the oil from the reservoir to the gear carrier when a negative “g” condition occurs.

A method of supplying lubricating oil to a reduction gearbox wherein the gearbox includes reduction gear stages and a gear carrier mounting at least a gear rotatable in the gear carrier and an associated bearing, the method comprising:

• forming a closed reservoir radially outwardly of the gear carrier within the reduction gear box, and a restricted opening to the reservoir for delivering lubricating oil through;
• forming an annular oil channel surrounding the gear carrier and in oil communication therewith;
• providing metered openings to communicate the reservoir with the annular oil channel so that the oil trapped in the reservoir is distributed into the oil channel to the gear carrier when a temporary pressure drop occurs in the oil delivery system.