The Air Oil Separator (AOS) is a Line Replaceable Unit (LRUs) used to remove air from the input fluid.
The separation is obtained through the cyclonic effect. The input aerated fluid is injected into the AOS.
The internal design of the AOS constraints the fluid to start a helicoidal motion along a hollow cylinder.
The internal geometry of the AOS produces a downward motion of the fluid and an upward motion of the air initially entrapped inside the fluid.
The outgoing fluid results de-aerated.