What does "sumping fuel tanks" involve?

Sumping fuel tanks involves draining a small amount of fuel from the lowest point of the tank to check for contaminants such as water, sediment, or other impurities. This process is critical for aircraft safety, as fuel tanks can accumulate contaminants that may settle at the bottom. By sumping the tanks, maintenance personnel can ensure that the fuel being used is free of these harmful substances, which could lead to engine performance issues or failures. This practice is important to maintain the integrity of the fuel system and to help prevent damage to the engine and other components.

Other options do not accurately describe the sumping process: completely removing all fuel is excessive and not the purpose of sumping, filling the tanks to maximum capacity does not involve inspecting for contaminants, and testing fuel pressure is a separate maintenance procedure related to the fuel system rather than assessing fuel quality through sumping.