The present work is the result of a research project carried out by the Politecnico di Torino with GE Avio S.r.l. The aim of this work is the study of the parameters of air oil static separators, also known as de-aerators, which are fundamental devices of the lube system for aero engines. The role of these components is to separate the air oil mixture coming from the scavenge line and to deliver the purified oil to the tank. The separation is accomplished without any moving part. The flow is provided with a swirling motion and the resulting centrifugal effects manages to separate the two phases thanks to their different density.