When I'm looking straight towards the sun even covered by cockpit frame the screen is getting pale.

Its a fsx feature called sun glare which works just as you describe.

 

Unfortunately Aces introduced a bug with SP2 and it  is turned on and off  by the same  menu item used for the DX10 preview setting.

So in SP2  it is always off in DX9 and always on in DX10 (as Dx10 preview is off in DX9 => sun glare off and on in DX10 -> sun glare on)

 

There is an option in the fixer misc dialog to hide the effect although this will also disable the rather similar G effects.