What is a potential indicator of a Straight Air rupture on a PA-4 train?

A potential indicator of a Straight Air rupture on a PA-4 train is the slow loss of Brake Pipe pressure. This situation occurs when there is a rupture in the air system, leading to a gradual decrease in pressure along the Brake Pipe. The braking system relies on maintaining a consistent and adequate pressure level in the Brake Pipe to ensure effective operation. If there is a rupture, the pressure will not remain stable, and rather than an immediate or sudden loss, it instead depletes slowly. This gradual decrease can provide critical information for operators, as it suggests a failure in the air system that could compromise train safety and effectiveness in braking.

In contrast, other options may not directly relate to the specific consequences of a Straight Air rupture. For example, brake pressure above 100 pounds does not indicate a rupture since a functioning system may still maintain high pressure. Loss of engine power is typically unrelated to air brake issues and could arise from different mechanical or electrical failures. Similarly, successive loud thuds while braking could signal other issues such as malfunctioning brakes or track irregularities, rather than indicating a specific rupture in the air system. Thus, recognizing the slow loss of Brake Pipe pressure is essential for diagnosing potential failures in the train's braking mechanism.