Originally Posted by
noooby
You would need to lose all four screens to not have any engine info. Power supply for the screens is separated.
The electrical fire/smoke checklist calls for switching GEN1 and GEN2 off and then BATTERY MAIN off. If you mistakenly switch off BATTERY MASTER instead of BATTERY MAIN at this point (and they are right next to each other) you will lose all electrical power and instruments. The engines will keep running fine, as they produce their own electrical power to do so.
Making this mistake in instrument conditions will result in loss of control and almost certainly game over. In my view quite a serious ergonomic design flaw of the 139, having those switches located together and named/labelled similarly.