View Full Version : A330 C OF G

23rd May 2006, 09:47
Apologies if this has been done to death but I have done a quick search and not found an answer.

How much influence on C of G calculation does the FMGEC have on the A330 automatic fuel transfer.

My current understanding is that the FMGEC only calculates the max and min MAC percentages. The auto fuel trim transfer then uses this info to protect the flight envelope.

However there is some confusion over this.


24th May 2006, 13:03
Its actually the FCMC the calculates the CG (& weight) based upon the ZFW and MACZFW you entered in the MCDU.

The FMGC uses the FCMC data for CG related fuel transfers.

That said the FMGC also computes its own data for use if both FCMCs fail.

26th May 2006, 21:29
It's a long while since I looked at this, but IIRC:

Crew input ZFW and ZFCG via the MCDU.
FM transmits this to the FMCG, which calulates a gross weight.
Incidently, GW and CG on the EWD are driven by the FCMC
Gross weight gives the CG target, which is used to calculate how much fuel to transfer aft.
FM acts as an independant monitor, and if it detects CG going to far aft, it tells the FCMC to transfer fwd.

Of course, the details are all pretty dependant on software levels and 200/300 / 340-600 etc.

27th May 2006, 11:25
All good answers so far.

What prompted this was a discussion along the lines of....

If you get a cargo shift or all the pax suddenly run to the front/back of the a/c, the initial C of G shift would be handled by the THS. However if this condition persisted would the fuel transfer system attempt to balance the aircraft?

Initially everyone thought no, but after some discussion about the FMGEC and it's 'envelope' protection function. Would this enable a fuel transfer? :confused: