Narrative:

There is a software glitch within airline's weight and balance software that led to a departure with incorrect weight calculations. The first officer had received the bag count from the ramp agent, and the passenger count from the gate agent and entered the numbers into the software. When on the weight and balance page, he allowed the software to calculate the ZFW center of gravity and takeoff center of gravity. The software came up with the error message, as the center of gravity was outside of limits. Following the suggestion of the software, he decided to 'split the cabin' in which he went back to the ZFW tab, then zeroed out the previous entries of 130 adults and 1 infant on the all rows page by placing a zero in the adult and infant fields and pressing the enter key after each entry. He then entered 72 adults and 1 infant in the passenger fields on the rows page, yet it was later discovered that he had not hit the enter key after placing these entries into their respective fields (as is required), and had used the tab button to move between entry fields. He then placed 58 adults in the passenger field on the other rows page, pushing the enter key as required. When he returned to the weight and balance page the center of gravity calculated within limits. He turned the computer to face me and I verified entries in the following fields, fuel, passenger, and bags/cargo. In brackets (beside the passenger field) was the figure 131. Assuming that the software had made the correct calculations of weight for 131 passenger, I entered the weights into the ACARS weight and balance report and we departed normally. As we were climbing through 7000 ft, I looked at the fuel prediction page and was surprised to see that it was forecasting arrival into jfk with 1000 more pounds than originally flight planned. When I crosschecked the gross weight with the flight plan, I noticed there was a large discrepancy. Climbing through 10000 ft, I asked the first officer for his laptop, and investigated the problem. I then realized that although the weight and balance page indicated 131 passenger, the 72 adults and 1 infant in 12 rows were not included in the passenger weight field (although it indicated 131 passenger). The error was verified by looking at the saved data text field. He had not pressed the enter key after these entries, and had tabbed from field to field. In the past tabbed entries would not show up on the weight and balance page passenger totals, only passenger numbers that were entered with the enter key. The weight and balance page indicated 131 passenger, yet the weight that was calculated beside the 131 figure was 72 passenger short (12960 pounds). We had departed with calculations made 12960 pounds short, and V1/vr speeds 6 KTS lower than required. I sent the proper weight and balance numbers via ACARS, and made a manual calculation of weight and changed the gross weight on the fuel page. Since the takeoff weight discrepancy was under planned takeoff weight operations did not generate an error message. We were rushed on departure due to being over 1 hour behind schedule, and we may have caught the discrepancy if we had had more time on the gate. However, short of doing manual calculations to verify the software has calculated the proper figures, the fuel total, passenger total and a weight in the baggage entry was crosschecked on the weight and balance page. The software needs to be changed so that passenger figures that were not followed by the enter key do not show up on the weight and balance page. The total passenger count should match the weight listed beside it.

Related reports:

Google
 

Original NASA ASRS Text

Title: DUE TO A MISCALCULATION OF WT AND BAL AND ACTUAL GROSS WT INFO, AN A320 PERFORMS A TKOF WITH A TRIM SETTING OUT OF LEGAL LIMITS FROM OAK.

Narrative: THERE IS A SOFTWARE GLITCH WITHIN AIRLINE'S WT AND BAL SOFTWARE THAT LED TO A DEP WITH INCORRECT WT CALCULATIONS. THE FO HAD RECEIVED THE BAG COUNT FROM THE RAMP AGENT, AND THE PAX COUNT FROM THE GATE AGENT AND ENTERED THE NUMBERS INTO THE SOFTWARE. WHEN ON THE WT AND BAL PAGE, HE ALLOWED THE SOFTWARE TO CALCULATE THE ZFW CTR OF GRAVITY AND TKOF CTR OF GRAVITY. THE SOFTWARE CAME UP WITH THE ERROR MESSAGE, AS THE CTR OF GRAVITY WAS OUTSIDE OF LIMITS. FOLLOWING THE SUGGESTION OF THE SOFTWARE, HE DECIDED TO 'SPLIT THE CABIN' IN WHICH HE WENT BACK TO THE ZFW TAB, THEN ZEROED OUT THE PREVIOUS ENTRIES OF 130 ADULTS AND 1 INFANT ON THE ALL ROWS PAGE BY PLACING A ZERO IN THE ADULT AND INFANT FIELDS AND PRESSING THE ENTER KEY AFTER EACH ENTRY. HE THEN ENTERED 72 ADULTS AND 1 INFANT IN THE PAX FIELDS ON THE ROWS PAGE, YET IT WAS LATER DISCOVERED THAT HE HAD NOT HIT THE ENTER KEY AFTER PLACING THESE ENTRIES INTO THEIR RESPECTIVE FIELDS (AS IS REQUIRED), AND HAD USED THE TAB BUTTON TO MOVE BTWN ENTRY FIELDS. HE THEN PLACED 58 ADULTS IN THE PAX FIELD ON THE OTHER ROWS PAGE, PUSHING THE ENTER KEY AS REQUIRED. WHEN HE RETURNED TO THE WT AND BAL PAGE THE CTR OF GRAVITY CALCULATED WITHIN LIMITS. HE TURNED THE COMPUTER TO FACE ME AND I VERIFIED ENTRIES IN THE FOLLOWING FIELDS, FUEL, PAX, AND BAGS/CARGO. IN BRACKETS (BESIDE THE PAX FIELD) WAS THE FIGURE 131. ASSUMING THAT THE SOFTWARE HAD MADE THE CORRECT CALCULATIONS OF WT FOR 131 PAX, I ENTERED THE WTS INTO THE ACARS WT AND BAL RPT AND WE DEPARTED NORMALLY. AS WE WERE CLBING THROUGH 7000 FT, I LOOKED AT THE FUEL PREDICTION PAGE AND WAS SURPRISED TO SEE THAT IT WAS FORECASTING ARR INTO JFK WITH 1000 MORE LBS THAN ORIGINALLY FLT PLANNED. WHEN I XCHKED THE GROSS WT WITH THE FLT PLAN, I NOTICED THERE WAS A LARGE DISCREPANCY. CLBING THROUGH 10000 FT, I ASKED THE FO FOR HIS LAPTOP, AND INVESTIGATED THE PROB. I THEN REALIZED THAT ALTHOUGH THE WT AND BAL PAGE INDICATED 131 PAX, THE 72 ADULTS AND 1 INFANT IN 12 ROWS WERE NOT INCLUDED IN THE PAX WT FIELD (ALTHOUGH IT INDICATED 131 PAX). THE ERROR WAS VERIFIED BY LOOKING AT THE SAVED DATA TEXT FIELD. HE HAD NOT PRESSED THE ENTER KEY AFTER THESE ENTRIES, AND HAD TABBED FROM FIELD TO FIELD. IN THE PAST TABBED ENTRIES WOULD NOT SHOW UP ON THE WT AND BAL PAGE PAX TOTALS, ONLY PAX NUMBERS THAT WERE ENTERED WITH THE ENTER KEY. THE WT AND BAL PAGE INDICATED 131 PAX, YET THE WT THAT WAS CALCULATED BESIDE THE 131 FIGURE WAS 72 PAX SHORT (12960 LBS). WE HAD DEPARTED WITH CALCULATIONS MADE 12960 LBS SHORT, AND V1/VR SPDS 6 KTS LOWER THAN REQUIRED. I SENT THE PROPER WT AND BAL NUMBERS VIA ACARS, AND MADE A MANUAL CALCULATION OF WT AND CHANGED THE GROSS WT ON THE FUEL PAGE. SINCE THE TKOF WT DISCREPANCY WAS UNDER PLANNED TKOF WT OPS DID NOT GENERATE AN ERROR MESSAGE. WE WERE RUSHED ON DEP DUE TO BEING OVER 1 HR BEHIND SCHEDULE, AND WE MAY HAVE CAUGHT THE DISCREPANCY IF WE HAD HAD MORE TIME ON THE GATE. HOWEVER, SHORT OF DOING MANUAL CALCULATIONS TO VERIFY THE SOFTWARE HAS CALCULATED THE PROPER FIGURES, THE FUEL TOTAL, PAX TOTAL AND A WT IN THE BAGGAGE ENTRY WAS XCHKED ON THE WT AND BAL PAGE. THE SOFTWARE NEEDS TO BE CHANGED SO THAT PAX FIGURES THAT WERE NOT FOLLOWED BY THE ENTER KEY DO NOT SHOW UP ON THE WT AND BAL PAGE. THE TOTAL PAX COUNT SHOULD MATCH THE WT LISTED BESIDE IT.

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.