NWS/Green/Yellow Syst.
Dream Land. Perhaps to taxi off after landing and after having had a green syst hyd failure.
SRover40. In the begining and also upto just a few years ago, the NWS was on the Green system and the pressure was tapped off the nose landing gear door closing circuit. In the event of a manual gear extension, the nose gear door remain open and thus isolating the NWS. So even if you still have green hyd qty one could not use the yellow + PTU to provide NWS.
Airbus have since moved the NWS system from the green hyd syst to the yellow syst. The NWS now has two sources of hydraulic power....No2 engine driven pump and the yellow hydraulic pump.
Not that I much like the idea, but you can, should you so desire, taxi on one engine and have NWS.
I hope this helps.
Ndicho Moja.