A320 - Indication on PFD
In the A320 the Fixed Aircraft Symbol is in black,and outlined in yellow. The yellow outline is dimmed if the flight crew selects TRK-FPA, unless the FMA is in TOGA or FLX mode.
Why is this design feature incorporated? Why should it be dimmed if TRK FPA is selected?
And why should it retain the brightness if TOGA or FLX mode is selected?