During an air test, what should be visually inspected concerning the helper consist?

During an air test, it is crucial to visually inspect that the brakes are applying correctly on the helper consist. This inspection ensures that the brakes are functioning as intended, which is vital for safe train operation. The purpose of the air test is to confirm that the entire braking system, including that of the helper locomotives, is operationally sound. Proper brake function contributes to the overall control and safety of the train, particularly when managing variations in train size and weight that can occur with helper units.

Inspecting the movement of the brake rigging and noting whether the brake shoes make contact with the wheels confirms that the pneumatic system is properly engaged and that the brakes are responsive. This step is critical before proceeding, as any failure in this area could lead to safety hazards during train operation.

The other choices do not directly relate to the air test's primary function of verifying brake performance. Speedometer readings, fuel gauges, and cargo load distribution are not the focus during an air brake test and do not affect the brake functionality that is being assessed with this specific inspection.