If the PSI indicator turns red during fueling, what action should be taken immediately?

When the PSI indicator turns red during fueling, this indicates that there is an abnormal condition that could pose a risk to safety or the fueling process. Therefore, the immediate and correct action is to stop fueling. This prevents potential hazards such as overpressurization, which can lead to leaks, ruptures, or other dangerous situations. It is essential to address any red indicators promptly to ensure the safety of personnel, the aircraft, and the fueling equipment.

Monitoring the process or continuing until the tank is full could exacerbate the problem if there is an ongoing issue, while calling for a supervisor may introduce delays that could compromise safety. Immediate cessation of fueling is the best practice in this scenario to mitigate any risks.