Narrative:

During preflight preparation we had an EPR mode inoperative performance problem to do in the aircraft. We were within 10 mins of departure with cabin door closed and jetway off aircraft when purser advised we had ill passenger in forward lavatory. This took me out of loop on the performance problem since I had jetway brought back to aircraft and a customer service representative supervisor come on board to consider removing passenger. We decided to go ahead and take passenger. When I returned to the cockpit the first officer and I reviewed the calculations but we both missed a mathematical subtraction error that equated to 10000 pounds. We were planning flaps 1 degree bleed off as this was the best runways performance numbers. When we subtracted 18.2 from 147.8 we came up with 139.6. We had long wait to take off and burned off enough fuel to depart weighing 139.6. At cruise we were discussing if dispatch runs the same numbers and what they came up with when I noticed the calculation we made was in error. Contributing factors were: 1) my distrs with customer service issue. 2) trying for on-time departure. 3) this was the end of 90 hour month plus and early get-up domicile time. 4) ACARS not being able to figure the penalty and maybe load planning should have known about the big weight penalty. Supplemental information from acn 704781: flight had been released prior to taking over the shift. I was briefed on the operation and reminded that flight had a placard for the EPR control modes specifically #2 engine EPR control mode inoperative. And that it was a placard that had to be handled manually. Having been released; I believed that the 'numbers' had been worked up for the reduction in ATOG. Aircraft left the gate on time but returned to the gate with sick passenger prior to takeoff. Also another problem I believe with ATC resulted in a somewhat chaotic situation. Aircraft departed the gate at XA45Z and took off at XB25Z. After arrival; captain called me and wanted to discuss the ATOG at departure. He thought they may have erred in the calculations; thus taking off approximately 10000 pounds heavier than their calculated weight. I took the flight manual and calculated the allowable takeoff weight using the prescribed formula in the book. After running it and using required interpolation I found maximum allowable takeoff weight was 129.1. Aircraft took off at 139.0. I see a significant problem particularly with the MEL itself. Under 'note: weight and v-spds must be calculated manually; request printout of EPR/ATOG message.' that phrase is listed under the flight crew heading instead of under the flight planning restrs. The entire planning procedure to calculate the lower ATOG needs to be part of 'flight planning restrs.' the dispatcher can work up the numbers and the crew could verify as a xchk in order to eliminate another incident like this one.

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Original NASA ASRS Text

Title: AN A320 CAPT AND DISPATCHER RPT A 10000 LB TKOF WT CALCULATION ERROR AFTER MANUALLY CORRECTING THE DISPATCH CALCULATION FOR AN MEL RESTR.

Narrative: DURING PREFLT PREPARATION WE HAD AN EPR MODE INOP PERFORMANCE PROB TO DO IN THE ACFT. WE WERE WITHIN 10 MINS OF DEP WITH CABIN DOOR CLOSED AND JETWAY OFF ACFT WHEN PURSER ADVISED WE HAD ILL PAX IN FORWARD LAVATORY. THIS TOOK ME OUT OF LOOP ON THE PERFORMANCE PROB SINCE I HAD JETWAY BROUGHT BACK TO ACFT AND A CUSTOMER SVC REPRESENTATIVE SUPVR COME ON BOARD TO CONSIDER REMOVING PAX. WE DECIDED TO GO AHEAD AND TAKE PAX. WHEN I RETURNED TO THE COCKPIT THE FO AND I REVIEWED THE CALCULATIONS BUT WE BOTH MISSED A MATHEMATICAL SUBTRACTION ERROR THAT EQUATED TO 10000 LBS. WE WERE PLANNING FLAPS 1 DEG BLEED OFF AS THIS WAS THE BEST RWYS PERFORMANCE NUMBERS. WHEN WE SUBTRACTED 18.2 FROM 147.8 WE CAME UP WITH 139.6. WE HAD LONG WAIT TO TAKE OFF AND BURNED OFF ENOUGH FUEL TO DEPART WEIGHING 139.6. AT CRUISE WE WERE DISCUSSING IF DISPATCH RUNS THE SAME NUMBERS AND WHAT THEY CAME UP WITH WHEN I NOTICED THE CALCULATION WE MADE WAS IN ERROR. CONTRIBUTING FACTORS WERE: 1) MY DISTRS WITH CUSTOMER SVC ISSUE. 2) TRYING FOR ON-TIME DEP. 3) THIS WAS THE END OF 90 HR MONTH PLUS AND EARLY GET-UP DOMICILE TIME. 4) ACARS NOT BEING ABLE TO FIGURE THE PENALTY AND MAYBE LOAD PLANNING SHOULD HAVE KNOWN ABOUT THE BIG WT PENALTY. SUPPLEMENTAL INFO FROM ACN 704781: FLT HAD BEEN RELEASED PRIOR TO TAKING OVER THE SHIFT. I WAS BRIEFED ON THE OP AND REMINDED THAT FLT HAD A PLACARD FOR THE EPR CTL MODES SPECIFICALLY #2 ENG EPR CTL MODE INOP. AND THAT IT WAS A PLACARD THAT HAD TO BE HANDLED MANUALLY. HAVING BEEN RELEASED; I BELIEVED THAT THE 'NUMBERS' HAD BEEN WORKED UP FOR THE REDUCTION IN ATOG. ACFT LEFT THE GATE ON TIME BUT RETURNED TO THE GATE WITH SICK PAX PRIOR TO TKOF. ALSO ANOTHER PROB I BELIEVE WITH ATC RESULTED IN A SOMEWHAT CHAOTIC SITUATION. ACFT DEPARTED THE GATE AT XA45Z AND TOOK OFF AT XB25Z. AFTER ARR; CAPT CALLED ME AND WANTED TO DISCUSS THE ATOG AT DEP. HE THOUGHT THEY MAY HAVE ERRED IN THE CALCULATIONS; THUS TAKING OFF APPROX 10000 LBS HEAVIER THAN THEIR CALCULATED WT. I TOOK THE FLT MANUAL AND CALCULATED THE ALLOWABLE TKOF WT USING THE PRESCRIBED FORMULA IN THE BOOK. AFTER RUNNING IT AND USING REQUIRED INTERPOLATION I FOUND MAX ALLOWABLE TKOF WT WAS 129.1. ACFT TOOK OFF AT 139.0. I SEE A SIGNIFICANT PROB PARTICULARLY WITH THE MEL ITSELF. UNDER 'NOTE: WT AND V-SPDS MUST BE CALCULATED MANUALLY; REQUEST PRINTOUT OF EPR/ATOG MESSAGE.' THAT PHRASE IS LISTED UNDER THE FLT CREW HEADING INSTEAD OF UNDER THE FLT PLANNING RESTRS. THE ENTIRE PLANNING PROC TO CALCULATE THE LOWER ATOG NEEDS TO BE PART OF 'FLT PLANNING RESTRS.' THE DISPATCHER CAN WORK UP THE NUMBERS AND THE CREW COULD VERIFY AS A XCHK IN ORDER TO ELIMINATE ANOTHER INCIDENT LIKE THIS ONE.

Data retrieved from NASA's ASRS site as of January 2009 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.