What is the primary requirement when air flowing a brake system for added cars using the Air Flow Method (AFM)?

The primary requirement when using the Air Flow Method (AFM) for adding cars is to charge the system to within 15 psi of the regulating valve setting. This process ensures that the brake system can properly equalize and achieve consistent pressure throughout the train, which is crucial for the effective functioning of the air brakes on all cars added to the system.

By charging the system within this specified psi range, it allows for adequate pressure to be maintained for reliable braking while accommodating the additional cars. This is important because if the pressure is too low, the brakes may not apply correctly, and if it is too high, it could lead to potential damage or failure in the brake components.

Other methods or requirements might focus on different aspects of the braking system, such as verifying brake functionality or monitoring air flow, but the focus on charging to within 15 psi for AFM specifically caters to achieving the right balance in pressure for effective brake operation across the added cars.