FO OF AN MD88 OVERSHOT DSCNT ASSIGNED ALT DURING A STAR ARR DUE TO THE #2 AUTOPLT DID NOT CAPTURE THE ALT. THE CAPT DISENGAGED THE AUTOPLT AND RETURNED TO ASSIGNED.

Narrative

I WAS THE CAPT AND PNF ON SEP/XA/98 MLU-DFW. WE WERE DSNDING INTO DFW ON THE CEDAR CREEK 2 ARR. WE WERE DSNDING TO CROSS TACKE INTXN AT 11000 FT MSL WITH THE #2 AUTOPLT ENGAGED IN IAS MODE. APCHING LEVELOFF ALT; THE FMA PANEL ANNUNCIATED ALT CAPTURE. THE ACFT DID NOT LEVEL OFF AND THE PF IMMEDIATELY SELECTED ALT HOLD. THE ACFT CONTINUED TO DSND; AT WHICH POINT I TOOK CTL OF THE ACFT AND MANUALLY FLEW BACK TO 11000 FT. I RE-ENGAGED THE AUTOPLT AND SELECTED ALT HOLD. THE ACFT BEGAN TO DSND AGAIN. I DISCONNECTED THE AUTOPLT; SELECTED THE #1 AUTOPLT (#1 DFGC); RE-ENGAGED THE AUTOPLT; SELECTED ALT HOLD AND THE AUTOPLT FUNCTIONED NORMALLY. DURING THE COURSE OF THIS EVENT; OUR MINIMUM ALT WAS 10700 FT MSL. WE RECEIVED A CALL FROM DFW APCH WITH A REMINDER THAT OUR CLRED ALT WAS 11000 FT AND HE REPEATED THE CURRENT ALTIMETER SETTING. AT THE TIME WE RECEIVED THIS CALL; WE WERE CLBING BACK TO 11000 FT. ON ARR AT THE GATE IN DFW; DFW MAINT WAS CALLED VIA RADIO AND INFORMED OF THE AUTOPLT MALFUNCTION. AN ENTRY WAS MADE IN THE ACFT LOGBOOK.