What is the primary purpose of a fuel tank sump in an aircraft?

A fuel tank sump serves a crucial function in the maintenance and safety of an aircraft's fuel system. Its primary purpose is to provide a designated area where contaminants such as water and dirt can accumulate. This accumulation is critical because water and particulates can adversely affect fuel quality, potentially leading to engine malfunctions or performance issues. Regularly draining the sump helps ensure that only clean, uncontaminated fuel is being pumped into the fuel system, thereby promoting the safety and efficiency of the aircraft’s operation.

The other options address different aspects that are not the primary function of a sump. For instance, while fuel storage and monitoring are essential, those functions are managed by other components of the fuel system. The maintenance of fuel temperature is also important, but it is typically managed by other system designs and not specifically by the sump. Therefore, the role of the sump in gathering impurities is essential for maintaining the integrity of the aircraft's fuel.