(...) if you keep in position 1 for too long, then position 1 will act like position 2, and position 2 will brake a little bit your train. In real life this can be solved only halting the train and walking through all of it, manually releasing the brakes on each car, and then going back to the cab and charging the brakes for 180 seconds. You may want to avoid this.
Errata corrige:
In theory, this would be true: the reference pressure in the wagons would be set to 0.54 MPa and so the train
should brake when the brake pipe is set at 0.5 MPa.
But...
The engineers weren't stupid and so isn't the FV4a. When the brake is in the 2nd position (the one normally kept whilst driving), if the pressure is above 0.5 MPa, air comes out through a calibrated hole, which makes that air noise you hear when you go from 1st to second position. This sets the pressure in the brake pipe from 0.54 to 0.5, but it is slow enough that brakes don't trigger.
So, why have I mentioned that problem?
With FV4a I don't think it's easy to make it happen, but in general setting the brake pipe to high pressures, especially at 0.7 MPa, can lead to all those problems that I listed. I heard a story of a shunting terminal where the shunting drivers always send 7 bar in the pipe and then the train drivers need to go through all the train. Fun stuff.
But anyway, if you keep the FV4a in the 1st position, you still have a problem: this position will act as the 2nd would normally do, and so you would lose the possibility to unbrake fast; that is because the wagons now "believe" that 0.54 is the normal pressure.
Am I pedantic? Well, it is quite likely!
Tried different simulator, break were responding better, it was much easier to feel it. Especially release mechanics seems to be little bit bad (too long). Also notice that EN-57 and other EZT has Knorr breaking system, locos has Oerlikon. It works different. Mind that long freights (500m+) are half kilometer long. Quite lot and it must take some time to pump cars break tank plus main pipe.
To me, TD2 looks fine when talking about brake behaviour. The only thing that makes it hard to control to me is that I have to use the keyboard, which is not designed for driving trains. But I'm just talking about impressions.
Sistonami I'm not sure about that LUZ in Poland could use independent breake as main. In US it is even advised to use it for stopping engine. Train breake is self applying on failure. Thats very important to automatic stop train if something bad happen.
I don't know about the pneumatic circuits in Polish locomotives, nor I'm an expert in PKP regulations, but I can talk from what I know about Italian locomotives (which shouldn't be
that different from the rest of Europe, right?): the loco has the brake pipe, as any wagon does, which goes to the connected wagons, the two brake levers in the cabs, a valve of the safety system, and the triple valve.
The latter is connected to the direct brake pipe; this pipe is connected also to the two direct brake levers in the cabs, and to the brake cylinders.
We can have special systems (G/P brake, high speed brake, etc.), but that is what you can find on almost every locomotive.
So, is there a difference between using the train brake or the direct brake? No. You're always just applying pressure to the direct brake pipe, but if you use the train brake lever you're going through the triple valve.
What happens if this pipe brakes? The same that happens if the brake cylinders lose air.
Remember that the main reason we're so worried about the brake pipe breaking is that part of it is made out of rubber pipes and metal joints going from one car to the other. It's so easy for it to break.