Why does the INBD & LOWER DU BRT controls have dual concentric rotary controls. ? The Outer/lower control, is the actual Brightness control. What does the Inner/Upper rotary knob do ? Note: The OUTER DU BRT has only the signle Rotary control (not a Dual Concentric one) Edited: OK, found the answer. The Inner Brightness control controls the Brightness of the WEATHER displayed data.As the PMDG 737NGX does not display "weather", their rotation has no effect in the PMDG Model.

It's also to brightens or dimming the TERR display on Navigation display.

It's also to brightens or dimming the TERR display on Navigation display.

Thanks Mark. That was not obvious from the Boeing Docs I read, ( It only mentioned Weather) but it would make sense to want to turn that down as well as the weather !!