Speeds on 330 340 PFD
Having flown the 3 aircrafts 320 330 340, I keep asking myself about how and where the characteristic speeds are computed.
On the 320 you can get the speeds from FMGC and PFD. Here we know that the FAC compute those speeds by using the AOA, N1, Altitude, THS and so on and present it to the PFD. Fine
We all know as well that sometimes by comparing the two (PFD and FMGC), we may have some discrepancies and therefore recompute the gross weight even if we know that Airbus recommends not to do so (old FCOM bulletin).
Now On the 330 340 (classic and not the newest version) The E part of FMGEC computes those speeds and presents them on the PFD but it uses the ZFW and ZFWCG from the Init page B and the fuel from FCMC. If you read FCOM 1, it does not say much but the FCTM says a bit more about it by telling us that the PRIM also interact with the FE.
My reasonning is: Can we get the same discrepancies between the PFD and the FMGEC on the 330 340 like on the little bus and recomputes the gross weight by applying the green dot computation math.
Sorry for being long and thorough.