Date: 201808
Local time of day: 1801-2400
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Takeoff / Launch
Aircraft component: PMC; Performance/Thrust Management Computer
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Time Pressure
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Airspace Structure; Human Factors
Primary problem: Ambiguous

Narrative: We were operating a flight and had loading delays that caused our slot time to be missed. ATC informed that we would have a 2 hour additional delay. They then called back and changed it to only 15 minutes delayed. This caused periods of idleness combined with periods of hurriedness to make the slot time. This hurry and wait and wait and hurry may have helped to throw us out of sequence. During the loading of the performance an entry of 227.4 was entered by the PF (Pilot Flying) as our ZFW (zero fuel weight). The performance data was printed; then entered into the FMS; and then briefed. As the 1st observer I compared the performance data with the load sheet looking at zero fuel; fuel and the TO CG. I failed to look at the TOGW. Had I been more thorough and deliberate I would have seen the ZFW should have been entered as 277.4 and was entered incorrectly. This caused us to take off with inaccurate data. The takeoff roll; rotation; and climb out seemed normal. It wasn't until we were entering the landing data (enroute) did we find our mistake. We noticed that the ZFW was 50;000 kg less and checked the performance data against the [previous performance calculations] to find that we had a V2 of 163 when it should have been 174. We realized that the plane was rotated and climbed out with too slow of an airspeed as a result of the miscalculation. We adjusted the ZFW and landed with correct data. Looking back I realize that as the 1st observer I should have slowed down and fully (not quickly) verified the performance data. I thought I saw 277.4 when it actually was 227.4 when reviewing the data. I should have checked the TOGW and then cross checked the V2 with the [previous calculations] and seen that a discrepancy of more than 5 kts existed. Although we did not experience any harm to the aircraft or ourselves it is a stark reminder of the hazards of rushing and the potential consequences of doing so. I have no recommendations as the procedures in place are adequate to catch errors of this type had we followed them slowly and deliberately while not allowing distractions to throw us out of sequence. It simply may have been the combination of rushing combined with a 4 man crew which often lulls us into thinking that someone else would catch any errors made by any one of us.


Second narrative: During preflight duties myself and the captain entered the incorrect (approximately 50;000 kg less than actual) zero fuel weight (ZFW) in both the performance section of the FMC and FDP (Flight Data Program) ACARS page (captain read the numbers; and I entered them for the FDP). I did not compare the 'stable' weight and balance ZFW to the FDP when the performance data came back on ACARS. All other policies and procedures were followed. We requested data for both an intersection and full length takeoff. We used the data for the intersection takeoff; thinking that it was the most conservative option (the data would be valid in the case of an intersection takeoff; and exceed performance requirements in the case of a full length takeoff). We were given a full length departure and departed normally. The Captain was the pilot flying. We discovered and corrected the error (for landing performance) when preparing for arrival (approximately 2 hours prior to landing).


Synopsis: B747 flight crew reported entering incorrect weight data and had a 50;000 kg difference from actual weight during takeoff.