Investigation of the spurious cases of ECAM warnings "FUEL: ZFW/ZFCG
DISAGREE" on A330/A340 basic aircrafts showed that when a ZFW/ZFWCG is inserted
on one MCDU, each FMS will send these values to their onside FCMC with a boolean
set to high (to indicate to the FCMC to init/re-init the values) during a few
seconds. But, the setting/resetting of the high position for this boolean is not
synchronized between both FMSs. A delta of more than 4 s may be observed.
And
because of the 3rd condition, the FCMC issues the message.
Excellent, thank you for that. So something akin to "a momentary lapse of communication".
Hi Old Grouch. Not intentionally; My PC, or the Pprune site were doing really
weird things to my attempted posts the other day - putting them in the middle of
the thread instead of at the end etc. If you can, please would you repost my
post?
Certainly, here we go:
Yes; pilot entered block fuel is used to make initial calculations according to the flight plan and winds.
This gives a gross error check; that the FMGEC (A330) agrees with the paper flight plan that fuel on board will be sufficient, given the winds, to complete the flight with sufficient reserve.
Later after engine start, the system refines its predictions based on actual fuel on board.
In our company we enter an estimated ZFW/ZFWCG after inputting the flight plan and winds. I've had the ECAM caution in question when taxying away after a turnaround in which we uploaded fuel, and after engine start (obviously). But ONLY when we have done a manual load sheet. I am trying to remember what we do differently with data inputs when we do a manual loadsheet. Perhaps we enter the estimates on one MCDU and the actuals on the other? Then if the FMGEC's don't talk to each other properly, we get the discrepancy and the caution?
Thank you, everybody who contributed.
