Narrative:

Flying on #2 autoplt, was given clearance to descend to FL200 during approach to rsw. Altitude was set and armed. Approaching leveloff, amber altitude light on FMA went out but autoplt failed to capture altitude. Aircraft noted passing through FL200 vertical speed wheel was rolled up and altitude hold selected. Aircraft stopped descent 400 ft below FL200. Vertical speed climb and FL200 reselected. Before reaching FL200 center issued clearance to 13000 ft. Same occurrence with autoplt leveloff at 13000 ft and subsequent 11000 ft clearance. However, closer monitoring prevented altitude deviation. Two other autoplt malfunctions during flight, related to turns. Autoflt write- up made at flight termination.

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Original NASA ASRS Text

Title: CAPT OF A SUPER MD80 DSNDED BELOW ASSIGNED ALT DURING DSCNT DUE TO AN AUTOPLT ALT CAPTURE PROB. HE RETURNED ACFT TO ASSIGNED ALT AND THEN CAUGHT ERROR BEFORE THE ACFT PASSED LEVELOFF ALT DURING SUBSEQUENT DSCNTS.

Narrative: FLYING ON #2 AUTOPLT, WAS GIVEN CLRNC TO DSND TO FL200 DURING APCH TO RSW. ALT WAS SET AND ARMED. APCHING LEVELOFF, AMBER ALT LIGHT ON FMA WENT OUT BUT AUTOPLT FAILED TO CAPTURE ALT. ACFT NOTED PASSING THROUGH FL200 VERT SPD WHEEL WAS ROLLED UP AND ALT HOLD SELECTED. ACFT STOPPED DSCNT 400 FT BELOW FL200. VERT SPD CLB AND FL200 RESELECTED. BEFORE REACHING FL200 CTR ISSUED CLRNC TO 13000 FT. SAME OCCURRENCE WITH AUTOPLT LEVELOFF AT 13000 FT AND SUBSEQUENT 11000 FT CLRNC. HOWEVER, CLOSER MONITORING PREVENTED ALTDEV. TWO OTHER AUTOPLT MALFUNCTIONS DURING FLT, RELATED TO TURNS. AUTOFLT WRITE- UP MADE AT FLT TERMINATION.

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.