What is the purpose of an air-oil separator, or deaerator, in a turbine engine oil tank?

• A. It removes water from the oil.
• B. It cools the oil.
• C. It filters contaminants from the oil.
• D. The swirling action releases air from the oil, and the air is used to pressurize the oil tank.

Answer: (D)

Air can become entrained in turbine engine oil as it circulates, which leads to foaming and inconsistent lubrication. The air-oil separator uses a swirl chamber so the oil spins and air separates from the oil. The oil continues back to the tank, while the separated air is routed to pressurize the oil tank. This pressurized air helps push oil through the system and maintains a steady, foaming-free supply to the bearings and pumps, ensuring reliable lubrication.