When should the brake handle be placed in the FULL SERVICE position during a main reservoir rupture?

Placing the brake handle in the FULL SERVICE position during a main reservoir rupture is critical for ensuring the safety of the train and its operations. The correct timing for this action is when loss of motor power occurs. When motor power is lost, there is a risk that train control can be compromised, leading to potential safety hazards. By activating the brake in FULL SERVICE at this moment, the engineer can help bring the train to a controlled stop, reducing the likelihood of an uncontrolled descent or collision, particularly if the train is on a slope.

Understanding this timing is crucial for maintaining control of the train during emergencies, as other scenarios like being in motion or having normal Brake Pipe pressure do not provide the urgency that a loss of motor power does. In addition, exceeding specific pressure levels in the Brake Pipe is not a relevant factor in deciding when to engage FULL SERVICE; the priority is ensuring immediate control in the event of a power failure.