THE CREW OF AN A319 HAD TO DISCONNECT MALFUNCTIONING AUTOPLT DURING ILS APCH.

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THE EVENT I'M ABOUT TO DESCRIBE WAS NOT REALLY A BIG DEAL. A BIG PART OF THAT MAY BE BECAUSE I HAD KNOWLEDGE OF A SIMILAR EVENT THAT HAPPENED TO ANOTHER CREW. THEIR STORY WAS DISSEMINATED TO OUR PLT GROUP; WHICH AIDED IN AN ALMOST INSTANT RECOGNITION OF WHAT WAS HAPPENING TO US. WE WERE COMING IN TO PIT FROM THE W. ATIS WAS RPTING RWY 28 AND RWY 32 IN USE. CONTACTING APCH; THEY GAVE US A HDG FOR RWY 10L AND TO DSND TO 4000 FT. I ASKED THE FO IF HE COULD GET DOWN IN TIME. THE RWY CHANGE MEANT WE HAD ABOUT 10 LESS MI TO GET DOWN. HE SAID HE THOUGHT HE COULD. WE JOINED THE LOC AND WERE TRACKING IT IN. AT 17 DME AND 8000 FT AGL; I SAID WE WERE TOO HIGH. 'HOW ABOUT A 370 DEG TURN TO LOSE SOME ALT?' HE SAID; 'GOOD IDEA.' WE ASKED FOR THAT AND RECEIVED IT. (IT WAS XA50 SO WE WERE THE ONLY ONES IN THE SKY AND WE WERE IN THE CLOUDS SO THE PAX WOULD NEVER NOTICE.) WE WERE DSNDING THROUGH 4400 FT FOR 4000 FT TO JOIN THE LOC AND TRACK IT IN TO CAPTURE THE GS. BECAUSE WE HAD BEEN ON THE LOC WHEN WE ROLLED OUT ON THE 080 DEG HDG TO JOIN THE LOC; WE WERE ONLY 1/10 MI FROM CTRLINE. WHEN THE APCH WAS ARMED; IT CAPTURED IMMEDIATELY AND STARTED A R TURN TO JOIN AS EXPECTED; BUT IT ALSO STARTED A VERY AGGRESSIVE CLB. I THINK IT HAD AN UNRELIABLE GS CAPTURE. WE CAUGHT IT VERY FAST. I DISCONNECTED THE AUTOPLT AND PUSHED THE NOSE DOWN AS FAST AS I COULD WITHOUT CREATING ANY NEGATIVE G'S BECAUSE WE STILL HAD FLT ATTENDANTS UP AND ABOUT; BUT STILL WENT FROM 4400 FT TO 5300 FT. THE AIRSPD WAS DROPPING FAST; BUT NEVER BECAME TOO SLOW. FOR ANOTHER CREW; NOT UNDERSTANDING WHAT WAS GOING ON; AIRSPD WOULD HAVE SOON BEEN A PROB. AFTER LNDG; I WAITED TO TELL THE CREW THAT WAS TO TAKE THE ACFT; AS WELL AS OUR MAINT PEOPLE. THAT'S WHERE THE FO PICKING UP THE ACFT TOLD ME HE HAD THE EXACT SAME THING HAPPEN TO HIM THE DAY BEFORE ON A DIFFERENT ACFT. THE MOST IMPORTANT THING HE TOLD ME WAS THAT THEY ALSO ARMED THE APCH LATE. THAT MADE ME WONDER IF THE AIRBUS SOFTWARE MIGHT HAVE SOME SORT OF A PROB HANDLING THE APCH BEING ARMED AT THE SAME TIME AS THE LOC IS BEING CAPTURED. A TEMPORARY SOLUTION MIGHT BE TO NOT ARM THE GS UNTIL AFTER THE LOC CAPTURE IF YOU ARE VERY CLOSE TO THE LOC WHEN CLRED FOR APCH.