Narrative:

About 1 yr ago my airline switched to another computer system in an effort to become Y2K compliant. Unfortunately our automated weight and balance suffered a great setback as compared to the old system. In an effort to become more automated, our operations engineering developed some new screens to help dispatchers automate takeoff and landing performance penalties. During this event, the B737-4 had anti-skid system, automatic ground spoiler system, and the left engine pmc all inoperative. The penalties were applied using the newly developed screens. Fortunately, the captain questioned the weight and balance numbers and asked to be sent new numbers without improved climb. Neither central load planning nor myself the dispatcher, could figure out how the flight was given improved climb takeoff weights when we did not initiate those numbers. Furthermore, we are not authority/authorized to use improved climb with anti-skid inoperative. It turned out that the automated screen used to apply takeoff weight penalties had used improved climb weights which gave an erroneous maximum takeoff weight that was 7000-8000 pounds too high. The flight returned to gate, but if it were not for the captain that knew by looking at his v-spds that this was an improved climb takeoff, the flight would have departed 4000 pounds overweight. It is my understanding that flcs are not specifically shown on their ACARS that the weight and balance numbers are based on improved climb or not. This aircraft along with the same MEL's had been flying the line previously for 3-4 days. Most likely the previous flts were all issued improved climb takeoffs when this was not authority/authorized and flcs along with dispatchers and load agents were not aware of this.

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Original NASA ASRS Text

Title: B737 PERFORMANCE COMPUTER DID NOT ACCOUNT FOR VARIOUS MEL ITEMS.

Narrative: ABOUT 1 YR AGO MY AIRLINE SWITCHED TO ANOTHER COMPUTER SYS IN AN EFFORT TO BECOME Y2K COMPLIANT. UNFORTUNATELY OUR AUTOMATED WT AND BAL SUFFERED A GREAT SETBACK AS COMPARED TO THE OLD SYS. IN AN EFFORT TO BECOME MORE AUTOMATED, OUR OPS ENGINEERING DEVELOPED SOME NEW SCREENS TO HELP DISPATCHERS AUTOMATE TKOF AND LNDG PERFORMANCE PENALTIES. DURING THIS EVENT, THE B737-4 HAD ANTI-SKID SYS, AUTO GND SPOILER SYS, AND THE L ENG PMC ALL INOP. THE PENALTIES WERE APPLIED USING THE NEWLY DEVELOPED SCREENS. FORTUNATELY, THE CAPT QUESTIONED THE WT AND BAL NUMBERS AND ASKED TO BE SENT NEW NUMBERS WITHOUT IMPROVED CLB. NEITHER CENTRAL LOAD PLANNING NOR MYSELF THE DISPATCHER, COULD FIGURE OUT HOW THE FLT WAS GIVEN IMPROVED CLB TKOF WTS WHEN WE DID NOT INITIATE THOSE NUMBERS. FURTHERMORE, WE ARE NOT AUTH TO USE IMPROVED CLB WITH ANTI-SKID INOP. IT TURNED OUT THAT THE AUTOMATED SCREEN USED TO APPLY TKOF WT PENALTIES HAD USED IMPROVED CLB WTS WHICH GAVE AN ERRONEOUS MAX TKOF WT THAT WAS 7000-8000 LBS TOO HIGH. THE FLT RETURNED TO GATE, BUT IF IT WERE NOT FOR THE CAPT THAT KNEW BY LOOKING AT HIS V-SPDS THAT THIS WAS AN IMPROVED CLB TKOF, THE FLT WOULD HAVE DEPARTED 4000 LBS OVERWT. IT IS MY UNDERSTANDING THAT FLCS ARE NOT SPECIFICALLY SHOWN ON THEIR ACARS THAT THE WT AND BAL NUMBERS ARE BASED ON IMPROVED CLB OR NOT. THIS ACFT ALONG WITH THE SAME MEL'S HAD BEEN FLYING THE LINE PREVIOUSLY FOR 3-4 DAYS. MOST LIKELY THE PREVIOUS FLTS WERE ALL ISSUED IMPROVED CLB TKOFS WHEN THIS WAS NOT AUTH AND FLCS ALONG WITH DISPATCHERS AND LOAD AGENTS WERE NOT AWARE OF THIS.

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.