This Irishman (or woman or not Irish) has nailed it on the head.
The 744 FMC (or for that matter all aircraft) have the pilots enter the ZFW of the aircraft (zero fuel weight being the dry weight plus payload).
What has been postulated is that there is no error message if the ZFW given is below the dry weight of the aircraft (in this case approximately 180 tonnes). Although I'm not sure if the 744 FMC software accounts for this fact.
So when the V-Speeds in the aircraft computer were calculated, the computer assumed that the gross weight of the aircraft (which is ZFW+Fuel) was say 250 tonnes (rather than the correct 350 tonnes for example).
The fuel wouldn't have been an issue as the fuel load is calculated at the dispatch office which assumes the aircraft is loaded correctly with the appropriate cargo and passengers.
|Quoting 777ER (Reply 5):|
I think the cause was because the B744 was overloaded, mostly with fuel
There is absolutely no way the dispatch fuel load could have been that badly overstated.
Remember the tanks of the 744 have about 177 tonnes of fuel capacity.