De-aerator in Oil System
 

Hi, not_a_mechanic here!

The gearbox is vented through a centrifugal breather, to separate the air/oil mist within it. But their is also a de-aerator that separates air bubbles from the oil supply being returned to the tank, right?? Is this also a centrifugal breather or does the de-aerator work on any other principle?

Looking forward to any response!

It's a metal splash-plate in a flat four.

On PT6A engines, the oil returning from the bearings drains into the accessory gearbox at the back of the engine where it de-airs. This is where the centrifugal breather is located.
From there, a scavenge pump sends the oil back to the oil tank after going through the oil cooler. The oil enters the oil tank from the top and a small metal plate shaped like a little bowl is deflecting the oil. I think I remember from the course that this is to prevent a solid jet of oil splashing straight into the oil tank which would add air the oil. That's why the call it de-aerator plate.

The prop reduction gearbox oil goes straight to the oil cooler and back to the tank because it doesnt have as much air in and already sits in the gearbox sump before being scavenged.

Many thanks for the clarification!