What is the first step in the procedure for uncoupling PA4 cars with the cab at the point of the cut?

The first step in the procedure for uncoupling PA4 cars with the cab at the point of the cut is to apply hand brakes on the section left behind. This action is critical for safety, as it ensures that the portion of the train remaining in position does not roll unexpectedly. By securing the cars with hand brakes, it limits any movement that could result from the uncoupling process, which is particularly important in maintaining control of the train as cars are separated.

In train operations, applying hand brakes before any uncoupling minimizes the risk of accidents or loss of train integrity, as gravity can cause unbraked cars to move. This is an established safety protocol, reinforcing that proper precautions are taken to secure the train before any operations are carried out.

The other steps, such as removing safety chains, inserting the cutting key, or charging the train, contribute to the overall process but do not precede the application of hand brakes. These actions typically follow the securing of the train to ensure a safe and smooth uncoupling.