I have also another question:
In the ARCHITECTURE above if P1 fails S1 takes over, so redundancy for rudder is still there. So why Blue Elec pumps starts again?
In another word, after ENG1 failure, the effect of PRIM 1 and PRIM 3 failures are not same. If PRIM 3 fails, no redundancy; if PRIM 1 fails there is still redundancy...(?)