Narrative:

Departed aby, contacted ZJX, heading assigned 310 degrees to 2000 ft initially, then to 5000 ft. After flying this heading a few mins, ZJX cleared us to naliz intersection to maintain 5000 ft. It was cool and we were climbing approximately 1800 FPM. Autoplt was engaged and altitude preselect set for 5000 ft. I diverted my attention briefly to the LORAN to set up direct course to naliz. I looked back and found aircraft had gone through 5000 ft to 5800 ft and the autoplt and altitude preselect were offline and climb had passed through assigned altitude. ZJX controller noted the error about the same time and called requesting my altitude. The aircraft had reached 6000 ft as I was beginning to correct and retrim. The controller stated that I had acknowledged the 5000 ft assignment to climb and maintain which is correct. He then assigned 6000 ft and shortly thereafter 7000 ft. The controller advised me to call and talk to quality assurance division of FAA which I did upon landing. I advised ZJX when asked to call quality assurance what had caused the altitude deviation (autoplt and altitude preselect failure or perhaps knocked off line by hitting the control wheel trim switch when I turned to reset the LORAN). I also reported this to quality assurance personnel by phone. I certainly recognize the potential danger of this equipment failure and will quicken my instrument scan in the future. Also plan to have the autoplt/altitude preselect system checked.

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Original NASA ASRS Text

Title: SMT PLT OVERSHOOTS ALT ON CLB.

Narrative: DEPARTED ABY, CONTACTED ZJX, HDG ASSIGNED 310 DEGS TO 2000 FT INITIALLY, THEN TO 5000 FT. AFTER FLYING THIS HDG A FEW MINS, ZJX CLRED US TO NALIZ INTXN TO MAINTAIN 5000 FT. IT WAS COOL AND WE WERE CLBING APPROX 1800 FPM. AUTOPLT WAS ENGAGED AND ALT PRESELECT SET FOR 5000 FT. I DIVERTED MY ATTN BRIEFLY TO THE LORAN TO SET UP DIRECT COURSE TO NALIZ. I LOOKED BACK AND FOUND ACFT HAD GONE THROUGH 5000 FT TO 5800 FT AND THE AUTOPLT AND ALT PRESELECT WERE OFFLINE AND CLB HAD PASSED THROUGH ASSIGNED ALT. ZJX CTLR NOTED THE ERROR ABOUT THE SAME TIME AND CALLED REQUESTING MY ALT. THE ACFT HAD REACHED 6000 FT AS I WAS BEGINNING TO CORRECT AND RETRIM. THE CTLR STATED THAT I HAD ACKNOWLEDGED THE 5000 FT ASSIGNMENT TO CLB AND MAINTAIN WHICH IS CORRECT. HE THEN ASSIGNED 6000 FT AND SHORTLY THEREAFTER 7000 FT. THE CTLR ADVISED ME TO CALL AND TALK TO QUALITY ASSURANCE DIVISION OF FAA WHICH I DID UPON LNDG. I ADVISED ZJX WHEN ASKED TO CALL QUALITY ASSURANCE WHAT HAD CAUSED THE ALTDEV (AUTOPLT AND ALT PRESELECT FAILURE OR PERHAPS KNOCKED OFF LINE BY HITTING THE CTL WHEEL TRIM SWITCH WHEN I TURNED TO RESET THE LORAN). I ALSO RPTED THIS TO QUALITY ASSURANCE PERSONNEL BY PHONE. I CERTAINLY RECOGNIZE THE POTENTIAL DANGER OF THIS EQUIP FAILURE AND WILL QUICKEN MY INST SCAN IN THE FUTURE. ALSO PLAN TO HAVE THE AUTOPLT/ALT PRESELECT SYS CHKED.

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.