When should all angle ***** be opened during the coupling procedure?

During the coupling procedure, all angle cocks should be opened before making the add. This practice is essential to ensure the operational readiness of the train and to allow for the proper flow of air throughout the system. When the angle cocks are opened before making the add, it helps to equalize the air pressure in both the locomotives and the cars, ensuring that the air brake systems can function correctly once the train is fully engaged.

Opening the angle cocks at the correct time prevents issues related to air pressure imbalances that could arise if they are opened after the locomotives and cars are already coupled. This timing ensures that any potential leaks can be addressed prior to coupling, contributing to operational efficiency and safety.