Narrative:

Incorrect software loaded in FMC. At my airline we fly 4 different models of the B737. On this day we were in a B737-500. The display on the FMC was different than other model '500's.' at first it appeared that the difference was just a software update change. In fact the software loaded was for a B737 model '700.' making a full power takeoff and using V speeds and approach vref speeds from a separate computer eliminated any errors. However, with the wrong software loaded, it would be possible to use incorrect power settings or reference airspds. 2 personal observations on this occurrence. First, I find it hard to believe there is not a failsafe design in place to prevent loading the wrong model software. Second, because I had flown the model '700' the previous day, seeing the wrong display in a '500' did not immediately raise a warning flag in my mind. Callback conversation with reporter revealed the following information: this reporter states on callback that he was surprised to learn that performance data meant for different version aircraft could be loaded into the wrong FMC. Reporter further states that there is no obvious indication in the cockpit or FMC CDU that draws attention to the version of software loaded on the FMC. He also reports that he believes this situation has been addressed by his company and that he has not heard any recent reports of this same problem.

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Original NASA ASRS Text

Title: RPTS OF INCORRECT FMC PERFORMANCE SOFTWARE INSTALLATION ON B737 ACFT.

Narrative: INCORRECT SOFTWARE LOADED IN FMC. AT MY AIRLINE WE FLY 4 DIFFERENT MODELS OF THE B737. ON THIS DAY WE WERE IN A B737-500. THE DISPLAY ON THE FMC WAS DIFFERENT THAN OTHER MODEL '500'S.' AT FIRST IT APPEARED THAT THE DIFFERENCE WAS JUST A SOFTWARE UPDATE CHANGE. IN FACT THE SOFTWARE LOADED WAS FOR A B737 MODEL '700.' MAKING A FULL PWR TKOF AND USING V SPDS AND APCH VREF SPDS FROM A SEPARATE COMPUTER ELIMINATED ANY ERRORS. HOWEVER, WITH THE WRONG SOFTWARE LOADED, IT WOULD BE POSSIBLE TO USE INCORRECT PWR SETTINGS OR REF AIRSPDS. 2 PERSONAL OBSERVATIONS ON THIS OCCURRENCE. FIRST, I FIND IT HARD TO BELIEVE THERE IS NOT A FAILSAFE DESIGN IN PLACE TO PREVENT LOADING THE WRONG MODEL SOFTWARE. SECOND, BECAUSE I HAD FLOWN THE MODEL '700' THE PREVIOUS DAY, SEEING THE WRONG DISPLAY IN A '500' DID NOT IMMEDIATELY RAISE A WARNING FLAG IN MY MIND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS RPTR STATES ON CALLBACK THAT HE WAS SURPRISED TO LEARN THAT PERFORMANCE DATA MEANT FOR DIFFERENT VERSION ACFT COULD BE LOADED INTO THE WRONG FMC. RPTR FURTHER STATES THAT THERE IS NO OBVIOUS INDICATION IN THE COCKPIT OR FMC CDU THAT DRAWS ATTN TO THE VERSION OF SOFTWARE LOADED ON THE FMC. HE ALSO RPTS THAT HE BELIEVES THIS SIT HAS BEEN ADDRESSED BY HIS COMPANY AND THAT HE HAS NOT HEARD ANY RECENT RPTS OF THIS SAME PROB.

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.