Ok Thanks, I found the option. And on overhead I set display on 2.Now the F/O and the captain PFD display the same altitude, but the warning message ALT Disagree remains.On the captain HUD, there was a disagree with F/O CAPT PFD.And why I have to put displays reference on F/O to have an altitude in accordance to the reality ?If I choose CAPT PFD as reference the altitude grows very low and it is not the real altitude