Originally Posted by
FMS_747
It appears that, on older FCOM, it was recommended to keep it on DIM position by night (Reason ? Case of Elec Emer Config ?) whereas I just can't find anything about it in our current FCOM version.
I'm not flying the A320 anymore, so my FCOM is outdated (18 DEC '12), but this was written at Preliminary Cockpit Preparation:
COCKPIT LIGHTS...................................................... ....................................................AS RQRD
DOME light should be on because it is the only lighting source in the EMER ELEC configuration. The DIM position is recommended for takeoff.
Note the "should" and "recommended". (Not "must" or "has to be")
There used to be an OEB for A320s with an analogue standby attitude indicator that stated that the dome light had to be on DIM at night.
This was because the standby attitude indicator wasn't illuminated in case of Elec Emer Config.
However, this OEB was cancelled after an electrical wiring update which kept the standby attitude indicator light on during an Elec Emer Config.