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.

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Original NASA ASRS Text

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

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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.