Booster discharge air is used for pressurization and cooling of the oil sumps.
The pressurization is achieved by a set of labyrinth seals, consisting of an air
seal and an oil seal. The difference of pressure between oil chamber and air
chamber causes the air to enter the oil chamber via the oil seals and therefore
prevents oil leaks. Venting of the air from the sump area is caused by the difference
of pressure between oil sump and ambient. The air is vented overboard
via centre air/oil separator, vent tube and flame arrestor.
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