Mmm..maybe i explained in a bad way myself.
If i have the 2 PACKS ON it's clear that i get the air from them to pressurize the cabin.
But, assuming we are performing a take off with
PACKS OFF, then i am not anymore supposed to get the air from the 2 PACKS that i turned OFF for performance reasons.
So the mode PREPRESSURIZATION during the take off roll, which i described before, in my opinion, should NOT work.
Because i don't find any evidence of the function of this mode with PACKS OFF i was wondering if anybody could have an answer if it's automatically inoperative or if it works in an another way (which i don't think).
I hope it's a little more clear now.
