What must never be done to a circuit breaker during non-emergency situations?

In non-emergency situations, it's essential to maintain strict control over the aircraft’s systems and prevent any unauthorized actions that could compromise safety or system integrity. Resetting a circuit breaker without permission from the flight deck undermines operational protocols and may lead to unintended consequences.

Circuit breakers are designed to protect electrical circuits from overloads and short circuits. When a circuit breaker trips, it indicates an issue that must be addressed. Resetting it without the flight deck's consent could lead to re-energizing a faulty circuit, which might result in more significant system failures or even pose safety risks.

The flight deck crew is trained to manage critical systems and has the knowledge and authority to determine the appropriate course of action. Therefore, any manipulation of circuit breakers should always be conducted with their explicit guidance, ensuring that all decisions are made with a full understanding of the potential implications.