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[ATLcrew]

Did it really?...

[ATLcrew]

Great question for an engineer. The document I have has formulas I'll never decipher....

[ATLcrew]

Apparently yes, they have that capability on the ground, at least on some serial #s and Mod #s. The ECAM would be what we discussed above and, again, it will only pop up when the T/O config button is pushed. I don't think it would pop up "when the thing won't rotate" since T/O INHIBIT mode will be active....

[ATLcrew]

So, I got an Airbus document from my Fleet Chief. It's a good 30 pages, most of it heavy engineering stuff that's so far beyond my feeble mind, it gave me cerebroalgia It appears that while FACs do not sense CG directly when on the ground, they can derive it from other data, such as pitch angle, weight, and even the amount of thrust that it takes to move the airplane (so FADEC is involved also). Since the FACs know what the CG range should be for a given weight, if they get information from all those sources that the CG may be out of that range, the above ECAM will be triggered.

Whether or not that would have helped this particular crew, I know not.

[ATLcrew]

That's just it, there is a check for THAT discrepancy AS WELL, and on some serial numbers that value and the actual trim value are all that are cross-checked. It appears, however, that there are software (and possibly hardware) versions that check for those two PLUS that "FAC-calculated value"....

[ATLcrew]

That's what I thought, too, and that appears to be the case on certain serial numbers. But on others, however, it appears the FACs are able to somehow calculate the CG themselves with the FQIC being some sort of an accessory to that process....

[ATLcrew]

Apparently they do have a way (depending on the mod status), because my manual says the message will be triggered if there is a discrepancy between

- Actual pitch trim from THSA
- The pitch trim value entered by the crew in the MCDU.
- The pitch trim value calculated by the FAC based on the CG (emphasis mine). I don't yet know exactly HOW the FACs calculate CG (but I do know who to ask) other than to say that, according to my diagram, the FQIC is involved somehow.

Stand by for further....

[ATLcrew]

Don't tell John Morgan and Dan Newlin....

[ATLcrew]

Ah, but they can! Research F/CTL PITCH TRIM/MCDU/CG DISAGREE. Also, research the "CHECK WEIGHT" MCDU scratchpad message.

The FACs are actually pretty smart....