A320, navigation lights, use of the switch (top panel)
Note: this switch is common to all versions of the 320 existing on FS and its use is therefore identical regardless of the version chosen.
How does it work, what is it for and how do we use it?
The switch in question turns on the navigation lights (red at the left wing tip, green at the right wing tip and white on the tail below the APU outlet) and illuminates the fin (this i.e. the "colors" of the company).
Note that the nav lights, once turned on, will remain on until the switch is positioned Off (i.e. the entire flight as long as the aircraft is powered on, including on the ground) while the drift lighting will not last only when the landing gears are compressed (i.e. the aircraft on the ground) and the flaps in position 1 or the slats extended (either on takeoff until switching to configuration 0 or on landing from the transition in configuration 1).
Three positions:
OFF: The system is turned off.
1: the system powers the navigation lights of set 1 and the left and right side fin lighting
2: the system powers the navigation lights of set 2 (a second set of bulbs... or LEDs for more recent versions) and the left and right side fin lighting
There is only one set of lights for the fin and it will be the same when ON in position 1 or 2.
How do we use it?
I would say the choice of the company...
Airbus recommends systematically setting position 1 and using position 2 as a backup. Indeed, to fly at night, the use of navigation lights is mandatory.
Which implies that if, for example, one of the lights is out of order in position 1 and the same or any other in position 2, the plane would not be able to fly at night...
Other companies may indeed also recommend using position 1 on odd days and position 2 on even days... why not, but that could increase the risk of a double simultaneous breakdown with identical wear on both systems.
Although the use of navigation lights is only mandatory at night, a "good practice" is to systematically turn the navigation lights ON as soon as the crew is on board. This allows ground personnel to be notified that the aircraft is powered on and in use.