Yesterday, I was on a flight and I felt bored during a long cruise. So I decided to give myself a challenge of handling an emergency. I tried to simulate both engine failure and APU generator failure so that I have no thrust and power but only standby instruments working.
As I shut down the engines and not turning the APU on, all of the instrument displays were dead.
Literally, all of them were dead including the standby instruments.
Standby instruments (aka, backup instruments) should be working all the time unless the master batteries are off so pilots can get basic information about their situations.
However, standby instruments in infinite flight have no point of being ‘Standby’. They need the master battery and APU to work just like the main displays like PFD and ND. We need a fix so standby instruments can actually work as ‘Standby’ instruments.