Why is there extra space in the oil tank?

The extra space in the oil tank is primarily designed to accommodate frothing and aeration of the oil as it circulates through the engine. When oil is pumped at high velocity, it can become agitated, leading to the formation of bubbles or froth. This phenomenon can increase the volume of oil temporarily and potentially decrease the effectiveness of lubrication due to the entrained air. Extra space in the oil tank ensures that even when frothing occurs, there is sufficient volume of oil available to maintain effective lubrication and cooling of engine components.

Including this additional space helps prevent situations where the oil could overflow or become aerated to the point where it affects the engine's performance. This ensures a consistent supply of oil under various operating conditions, including during rapid changes in engine speed or direction.

The other reasons, such as fire protection, accommodating extra oil for long flights, and anti-surge action, pertain to specific operational requirements but do not fundamentally address the impact of frothing and aeration on oil levels and lubrication effectiveness.