Originally Posted by
Uplinker
What, ALL the screens? - leaving you with just the standby instruments and nothing else?
I disagree. A navigation problem alone should not blank the attitude, IAS, TAS, altitude, V/S, A/P status, A/THR status, N1, EGT, etc, etc. You should just get a red flag for; heading, G/S, wind vector, ILS, VOR, map, compass, course, or whichever Nav function is unavailable, or disagrees with the other side. The whole bloody screen shouldn’t blank, nor should the screens which don’t display any Nav info.
I have problems understanding how a fault in the nav data or its processing can cause displays to blank. I always understood from the various schematics that the Flight Management Computers, Flight Control Computers and Display Processors are physically separate boxes connected by a data bus. In this case the displays should only get turned off if they received an "off" command - surely loss of signal from a crashed FMC should produce an error display rather than a blank screen?
On the other hand if the boxes on the schematics represent logical components run on the same hardware, the plot thickens. What else stopped working when the displays blanked?
Perhaps someone in the know can chip in?