A reduction gearbox for a gas turbine engine may have one or more epicyclic gear trains used for speed reduction and to transmit power. The planet gears, part of the epicyclic gear train, are typically mounted on journal bearings. The bearings must be continuously fed with lubricating oil for adequate operation. Various manoeuvres can occur during flight, and some of these manoeuvres can affect momentarily the lubricating oil operating pressure. Under manoeuvres generating a negative “g”, the oil system pressure may drop significantly to the extent that the oil flow delivered to the journal bearings may be interrupted.
There exist systems for delivering lubricating oil to bearings in a reduction gearbox, to avoid the starving of the bearings during negative “g” circumstances, which systems include additional pumps and/or valves to supplement the lubricating oil system.
There is a need for a system to retain lubricating oil around the bearings, in a reduction gearbox, that is simple and requires fewer accessories in order to provide protection against oil starvation of the bearings during negative “g” circumstances.