Jet* planning software is limited in that if a flight is overbooked, the data resets itself. Ie. if the a/c has 200 seats for example and the flight has 201 seats booked, the planner clocks itself and shows the pax numbers as 1!
News to me, however I think the dumbest pilot would look at that and be a little suspect, only time I carried close to 1 pax was on a ferry. Also, normally, most guys/gals carry enough " fat " to cover the difference in fuel burn, especially on a long night flight.
I seriously hope that I have been misinformed and that someone will shoot this theory down.
Yes you have, there is no way they would have blasted off with a difference in pax of that magnitude, or any magnitude for that matter, the PDA docket has to match the Cabin Crew count, simple.
Surely there must be more to this turn-back than what is being written here?
Yep, you can bet on it, I don't know but as mentioned earlier PH wx forecast is quite often dodgy, especially with fog.
If the ZFW increased dramatically preflight (and entered in FMC) wouldnt the FMC produce a scratchpad message to the effect "insufficient fuel"
No
If the ZFW error was not identified & the wrong ZFW entered into the FMC. Then wouldnt all the takeoff calculations of takeoff speeds & thrust be in error.
V speeds are manually inserted by the pilots, which are taken from the TOLD card after obtaining from the RTOW book
Is there a ECAM message something like "STAB BAND" which would appear if the FMC programmed weights differ to that in which the nose gear senses as actual aircraft weight?
No such message, and to the best of my knowledge, no weight sensor in nose gear. The only message that even slightly applies to the above is " CHECK GW " which only shows if the FMC and FAC computed weights differ by more that
7T. (this is based on pilot inserted data, and the GW computed by the FAC via AoA etc )