The way I look at it, there is no ZFW nor ZFCG computation. They are
always pilot entered.
Absolutely correct. Perhaps I wasn't clear earlier. When I said "...and the consequent difference in the result of a particular calculation that the FCMCs and FMGCs each do", I meant a calculation that
uses ZFW/ZFWCG values to derive another value (the GW/GWCG), not a calculation that
reults in in the ZFW/ZFWCG. The ZFW/ZFWCG are indeed always pilot-entered and, of course, are the starting point of the calculations.
It is clearly a fuel related discrepancy
I quite agree. Incidentally, when we got this message, like
Romasik says
, we had indeed not uplifted any fuel on a turnaround.
We can apply the relevant procedure, but without knowing the 'thought process' of the system behind the message, it's difficult to gain a full understanding of it and its background.