What is the purpose of the hopper tank?

The primary purpose of the hopper tank in an aircraft is to permit a fast warm-up of the engine oil. This is significant because during cold weather operations or after extended periods of inactivity, engine oil needs to reach its optimal operating temperature to ensure proper lubrication and performance. The hopper tank provides a means to preheat the engine oil, which is essential for maintaining engine health and efficiency.

In this context, the other options do not accurately represent the function of the hopper tank. While storage of excess fuel and management of fuel pressure are important aspects of fuel system design, they do not apply to the specific purpose of the hopper tank. Additionally, filtering contaminants from fuel is typically handled by different components in the fuel system, such as fuel filters, rather than the hopper tank itself. Therefore, the option related to the fast warm-up of engine oil is the most accurate representation of the hopper tank's function in aircraft systems.