Narrative:

During climb out the aircraft was on autoplt and coupled to the performance computer. The first officer was flying. 10000' was set and armed in the altitude window. The aircraft leveled off at 10000', and the FMA showed that it was in the performance cruise mode. It was accelerating and the first officer was entering a cruise speed of 280 KTS in the performance computer. I was doing the 10000' check. The altitude warning horn went off at 10200'. The first officer disengaged the autoplt and autothrottles and flew it back to 10000'. We had reached 10300' before going back to 10000'. We inspected the performance computer and discovered it had dumped some of its data and would not accept commands. Should we trust these computers? One never knows when they will fail!

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Original NASA ASRS Text

Title: ACR MLG AUTOPLT FAILS TO CAPTURE ALT IN CLIMB.

Narrative: DURING CLBOUT THE ACFT WAS ON AUTOPLT AND COUPLED TO THE PERFORMANCE COMPUTER. THE F/O WAS FLYING. 10000' WAS SET AND ARMED IN THE ALT WINDOW. THE ACFT LEVELED OFF AT 10000', AND THE FMA SHOWED THAT IT WAS IN THE PERFORMANCE CRUISE MODE. IT WAS ACCELERATING AND THE F/O WAS ENTERING A CRUISE SPD OF 280 KTS IN THE PERFORMANCE COMPUTER. I WAS DOING THE 10000' CHK. THE ALT WARNING HORN WENT OFF AT 10200'. THE F/O DISENGAGED THE AUTOPLT AND AUTOTHROTTLES AND FLEW IT BACK TO 10000'. WE HAD REACHED 10300' BEFORE GOING BACK TO 10000'. WE INSPECTED THE PERFORMANCE COMPUTER AND DISCOVERED IT HAD DUMPED SOME OF ITS DATA AND WOULD NOT ACCEPT COMMANDS. SHOULD WE TRUST THESE COMPUTERS? ONE NEVER KNOWS WHEN THEY WILL FAIL!

Data retrieved from NASA's ASRS site as of August 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.