Final answer:
If fuel flow does not stop during a fuel flow precheck in a concurrent servicing operation, immediate action must be taken to stop the flow, engage the emergency shut-off, and inspect and repair the fuel system.
Step-by-step explanation:
If the fuel flow does not stop during the fuel flow precheck of a cargo/passenger aircraft concurrent servicing operation, immediate action should be taken to ensure the safety of the operation and to prevent a potential hazard. The standard procedure is to first attempt to stop the fuel flow using the normal controls. If this does not work, the emergency fuel shut-off should be activated to halt the fuel supply. Once the situation is under control, it is essential to investigate the cause of the failure to prevent future occurrences. Maintenance personnel should inspect the fuel system for defects or malfunctions, and proper repairs should be conducted before returning the aircraft to service. It is imperative that all personnel understand the importance of following these safety protocols to maintain a safe operating environment.