B747 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Situational Awareness; Distraction; Confusion; Troubleshooting
Deviation / Discrepancy - Procedural Weight And Balance; Deviation / Discrepancy - Procedural Published Material / Policy
General Release Refused / Aircraft Not Accepted
Aircraft; Human Factors
During preflight; I was assisting the Captain with duties. When we received the SABLE; I entered the ZFW and TOW MAC into the Performance page of ACARS; all other entries were already loaded; and pushed 'SEND'. We received the ACARS Aerodata/FDP a short time later; the Captain was preoccupied working a MEL (No Water) and asked me to enter the data into the FMS. I entered the ZFW and moved on to the TAKEOFF/THRUST pages; this is when I first noticed something wrong. We were very light weight; small amount of cargo and a small BLOCK fuel requirement (32.3); for the short flight (ZZZZ-ZZZZ1). The FDP data was THR: TO and no ATM; I loaded the FMS but my brain was struggling with why we would need TO thrust with no Assumed Temperature?When I finished the FMS entries I presented the paperwork to the Captain and the Observer Pilot for verification and mentioned to them that THR: TO and no ATM seemed very odd. The two of them agreed that the data seemed odd and the three of us began looking for what we screwed up in the 'data entry'. We searched everything we could think of; but could find nothing wrong. The TLR (Takeoff/Landing Report) even showed an Assumed Temperature. The Captain decided to call Dispatch and have them compute a 'Live Calculation'; the Captain began giving the Dispatcher the parameters for the 'Live Calculation'. Sometime during this process the Dispatcher identified that there had been some similar problems lately like this and then identified that the '...B1F engines required a TOGW of 240K...' ( I've never heard of this nor have I been able to find it in any of our publications.) The Dispatcher had us standby while he calculated a new Block fuel. The Dispatcher changed our Block fuel to 58.0 and sent us a new OFP 'Front Page'. We had to have the stairs put back in place and begin the process of ordering more fuel and getting the paperwork straightened out. I have included pictures of everything except I missed getting the new SABLE and FDP copy; it had the increased GRWT; an ATM of 63 and a N1 of 95.9. I would like to add that the actual T/O had an extremely fast acceleration at an N1 of 95.9; I'm not 100% positive but I feel that had we not caught this mistake and used the N1 of 105.6 we would have been above either MCG; MCA; or both. Seemed like a very dangerous and unsafe situation was narrowly avoided. NOTE: I flew KC-135s for 25 years and 'Performance' was never our limiting factor; 'Control' was always our concern. I was concerned when I saw the FDP data - One of those 'hair on the back of my neck' moments. Not sure about the 'CF6-80C2-B1F... 240K' requirement. I know that these engines with NG FMS are limited to TO only but I (we) might need a reminder of the >240K requirement and where to find it.
Air carrier First Officer reported confusion after reviewing the fuel load for the flight.