Narrative:

During the last yr my carrier has initiated a contract with xyz to provide a comprehensive package of services, including computerized performance and weight and balance computations. On a number of occasions, I have noticed that various of the aircraft which were included in this contract did not perform as they might have been expected (ie, difficulty lifting off due to mistrim, nose coming off the ground early, aircraft unable to climb to planned altitudes). The final weight and balance and performance data is provided to us by ACARS printout. We received a 'final' ACARS closeout which was predicated on a takeoff weight of 404,000 pounds. This varied from our planned' takeoff weight by about 20000 pounds, however, such variations are not unusual. All takeoff bugs and trim was set for the 404,000 pound weight, and we planned on a runway and flap setting which would not have been possible at the higher (424000) weight. Due to an ATC delay, the flight engineer made a routine call to advise local operations personnel about the delay. At that point we determined that the ACARS information was wrong. Where we had been trained that ACARS was always the latest and best information available, our own investigation showed that the data can easily be wrong. In fact, I now believe that it is often wrong, and there are few clues which might lead a crew to question the data.

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Original NASA ASRS Text

Title: WRONG RWY TKOF PLANNED ON MISREPRESENTED ACFT GROSS WT.

Narrative: DURING THE LAST YR MY CARRIER HAS INITIATED A CONTRACT WITH XYZ TO PROVIDE A COMPREHENSIVE PACKAGE OF SVCS, INCLUDING COMPUTERIZED PERFORMANCE AND WT AND BAL COMPUTATIONS. ON A NUMBER OF OCCASIONS, I HAVE NOTICED THAT VARIOUS OF THE ACFT WHICH WERE INCLUDED IN THIS CONTRACT DID NOT PERFORM AS THEY MIGHT HAVE BEEN EXPECTED (IE, DIFFICULTY LIFTING OFF DUE TO MISTRIM, NOSE COMING OFF THE GND EARLY, ACFT UNABLE TO CLB TO PLANNED ALTS). THE FINAL WT AND BAL AND PERFORMANCE DATA IS PROVIDED TO US BY ACARS PRINTOUT. WE RECEIVED A 'FINAL' ACARS CLOSEOUT WHICH WAS PREDICATED ON A TKOF WT OF 404,000 LBS. THIS VARIED FROM OUR PLANNED' TKOF WT BY ABOUT 20000 LBS, HOWEVER, SUCH VARIATIONS ARE NOT UNUSUAL. ALL TKOF BUGS AND TRIM WAS SET FOR THE 404,000 LB WT, AND WE PLANNED ON A RWY AND FLAP SETTING WHICH WOULD NOT HAVE BEEN POSSIBLE AT THE HIGHER (424000) WT. DUE TO AN ATC DELAY, THE FE MADE A ROUTINE CALL TO ADVISE LCL OPS PERSONNEL ABOUT THE DELAY. AT THAT POINT WE DETERMINED THAT THE ACARS INFO WAS WRONG. WHERE WE HAD BEEN TRAINED THAT ACARS WAS ALWAYS THE LATEST AND BEST INFO AVAILABLE, OUR OWN INVESTIGATION SHOWED THAT THE DATA CAN EASILY BE WRONG. IN FACT, I NOW BELIEVE THAT IT IS OFTEN WRONG, AND THERE ARE FEW CLUES WHICH MIGHT LEAD A CREW TO QUESTION THE DATA.

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.