What action must be taken if a ruptured air hose is discovered while preparing a train?

When a ruptured air hose is discovered while preparing a train, it is crucial to change the air hose because it plays a vital role in the brake system's operation. If the air hose is damaged, the brake pipe will not be able to pressurize properly, which is essential for the brakes to function effectively throughout the train.

The brake pipe carries compressed air from the locomotive to each car's braking system. A ruptured hose interrupts this air flow, leading to a failure in the brake system and potentially compromising safety. Therefore, ensuring that the air hose is intact and functioning is critical to allow the entire system to operate correctly.

This understanding highlights the importance of routine inspections and maintenance in train operations, which ensures safety and reliability during transit.