Narrative:

After liftoff our flight management guidance comptuer (FMGC) gave us a 'check gross weight' message, the first officer was flying. He thought the aircraft seemed slow to liftoff. At cruise we checked the weight tab and although the passenger count was correct (150), the zero fuel weight did look low. We called dispatch and he researched the problem. Dispatch called back with an answer. Load control had mistakenly entered our passenger load as 150 children. 'Half weights' had been used to generate our zero fuel weight. Our original weight tab ZFW was 13200 pounds low. In other words we were 13200 pounds heavier than we thought. During taxi-out, at night, at a busy hub. I failed to notice our gross weight was lower than it should have been. Both the first officer and I followed our SOP's. We don't check zero fuel weight for reasonableness, however, I think I will do a few personal calculations from now on, to make sure I don't miss a mistake again.

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Original NASA ASRS Text

Title: FLC OF MLG TKOF WITH THE WRONG WT AND BAL COMPUTATION BY 13000 LBS LIGHTER THAN ACTUAL WT OF THE ACFT.

Narrative: AFTER LIFTOFF OUR FLT MGMNT GUIDANCE COMPTUER (FMGC) GAVE US A 'CHK GROSS WT' MESSAGE, THE FO WAS FLYING. HE THOUGHT THE ACFT SEEMED SLOW TO LIFTOFF. AT CRUISE WE CHKED THE WT TAB AND ALTHOUGH THE PAX COUNT WAS CORRECT (150), THE ZERO FUEL WT DID LOOK LOW. WE CALLED DISPATCH AND HE RESEARCHED THE PROB. DISPATCH CALLED BACK WITH AN ANSWER. LOAD CTL HAD MISTAKENLY ENTERED OUR PAX LOAD AS 150 CHILDREN. 'HALF WTS' HAD BEEN USED TO GENERATE OUR ZERO FUEL WT. OUR ORIGINAL WT TAB ZFW WAS 13200 LBS LOW. IN OTHER WORDS WE WERE 13200 LBS HEAVIER THAN WE THOUGHT. DURING TAXI-OUT, AT NIGHT, AT A BUSY HUB. I FAILED TO NOTICE OUR GROSS WT WAS LOWER THAN IT SHOULD HAVE BEEN. BOTH THE FO AND I FOLLOWED OUR SOP'S. WE DON'T CHK ZERO FUEL WT FOR REASONABLENESS, HOWEVER, I THINK I WILL DO A FEW PERSONAL CALCULATIONS FROM NOW ON, TO MAKE SURE I DON'T MISS A MISTAKE AGAIN.

Data retrieved from NASA's ASRS site as of July 2007 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.