Narrative:

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 pilot group, which aided in an almost instant recognition of what was happening to us. We were coming in to pit from the west. ATIS was reporting runway 28 and runway 32 in use. Contacting approach, they gave us a heading for runway 10L and to descend to 4000 ft. I asked the first officer if he could get down in time. The runway change meant we had about 10 less mi to get down. He said he thought he could. We joined the localizer and were tracking it in. At 17 DME and 8000 ft AGL, I said we were too high. 'How about a 370 degree turn to lose some altitude?' 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 passenger would never notice.) we were descending through 4400 ft for 4000 ft to join the localizer and track it in to capture the GS. Because we had been on the localizer when we rolled out on the 080 degree heading to join the localizer, we were only 1/10 mi from centerline. When the approach was armed, it captured immediately and started a right turn to join as expected, but it also started a very aggressive climb. 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 flight attendants up and about, but still went from 4400 ft to 5300 ft. The airspeed was dropping fast, but never became too slow. For another crew, not understanding what was going on, airspeed would have soon been a problem. After landing, I waited to tell the crew that was to take the aircraft, as well as our maintenance people. That's where the first officer picking up the aircraft told me he had the exact same thing happen to him the day before on a different aircraft. The most important thing he told me was that they also armed the approach late. That made me wonder if the airbus software might have some sort of a problem handling the approach being armed at the same time as the localizer is being captured. A temporary solution might be to not arm the GS until after the localizer capture if you are very close to the localizer when cleared for approach.

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Original NASA ASRS Text

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

Narrative: 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.

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.