Aero tech
What is your fixation with in-flight shut downs. All of your threads start with “with an engine shut down or all engines flamed out”
Engine manufactures go to great lengths to make sure this does not happen and if airlines maintenance become lax and in-flight shut down occurs the external governing bodies FAA JAA CASA etc remove etops or shorten operating etops limitations from 240 minutes to 120 or 180mins to 135 mins etc as applicable.
I mention this to emphasise how important it is to any airline operating large twin engine jet aircraft NOT to have in in-flight shutdown.
Your Backup Generator is a wild frequency generator used in case of main generator failure (IDG) to provide a separate power to flight control/ auto pilot computers etc.. “Essential power”
Check your mail for the rest..
I hOPE THIS HELPS