What should be done to pre-check a drop tank during refueling?

To pre-check a drop tank during refueling, utilizing the external pre-check switch located in fuel door 8 is essential. This switch allows the crew to verify that the fuel system is functioning correctly and ensures that the necessary fuel levels and flow rates are achieved before the refueling process begins. It's an important step in the safety protocol, as it helps prevent potential issues during refueling that could lead to fuel leaks or improper fueling.

Other actions, such as closing all valves or checking fuel levels from the cockpit, while valuable in their own contexts, do not specifically address the pre-check procedure for the drop tank. A visual inspection of the tanks can be a good practice but does not replace the importance of using the pre-check switch, which provides the necessary verification of system integrity and readiness for safe refueling operations. Therefore, the use of the external pre-check switch is a critical step in ensuring proper fueling procedures.