B747-400: BAT switch with APU running
Good morning folks.
We had a discussion in the cockpit last night regarding what would happen if the BAT switch was turned OFF during ground operations with the APU running, APU generators connected and STBY POWER switch in AUTO. We all imagined that "nothing" would happen, considering that the relevant busses would be fed by the AC system.
Allegedly, someone turned BAT OFF by an accident in mentioned condition and everything went black and the APU subsequently shut down. Could anyone please explain why?
Best regards,
Bluescan