Any more on the previous report that the APU battery charger takes it's supply off the F/O's Instrument supply bus?
Yeah, I shook my head too when I read it.........they wouldn't would they...
From a post by
gas path in
http://www.pprune.org/rumours-news/5...arning-12.html
post 224
The four engine driven generators supply the 235v variable freq. That goes to the aft and fwd EE bays. The aft EE bay Auto TRU's convert to +/-270vDC.
The DC is for driving the cabin air compressors, centre hyd. pumps. O/Jett pumps, the ram fans, and the NGS compressor.
The APU battery located in the same bay supplies the APU Hot Batt Bus its charger is supplied from the F/O's instrument bus. APU starter 235vac from the ATRU.
The main a/c battery located fwd. is charged (via a charger) from the capt's instrument bus. This is the only one with a diode pack to prevent the Hot batt. bus from back feeding the battery.
The PMG's only power the eng. EEC's
Windmilling engines will provide some hydraulic power. Enough for flight controls.
The RAT will supply hydraulic power to the centre hyd. system.
The RAT will supply electrical power to the ac busses (with some serious load shedding!) but primarily the backup bus, flt. instrument busses, brake system controllers (130VDC)
I'm tired its getting late..so apologies if I've got something wrong.
So the possibility, however slight, of a cascading battery failure [s] dragging down the supply buss[es] for both "sets" of instruments?
that can't be right surely.....
