Question for an experienced Boeing avionics engineer
 

One question which has puzzled our 787 pilots since the type was introduced concerned the overhead panel illuminated switches. The switches with a line / bar across only illuminate in the top half (all others seem it have upper and lower illumination). What is the purpose / reason for this bar? Can the two switches be swopped if modified? We spend hour’s sitting there with little going on and it’s strange that none of the guys I fly with have any idea on this.Thanks

The line/bar you are referring to is to indicate that part of the switch has no indication/warning in that part. I assume it is done so all the switches are the same physical size, with the other 'two part' switches having either fault/inop/press indications in the lower half [where the line is in the switches you are referring to]

The Boeing 787 switches are modules with LEDs, so the whole module is replaced when the switch is faulty, the internals cannot be switched around, as on older Boeing types [that also had replaceable lamps]

Quality answer thanks for that.

Dark Cockpit Concept
 

As stated the "bar/line" means that part of the switch is inactive (not actively used). Going along with the "dark cockpit" concept means the fewer lights and fewer distractions the better. Swapping parts that are not approved i.e. the IPC shows interchangeability.

Great thanks.