AN A319 CREW; ON APCH TO DTW; EXPERIENCED AN UNEXPLAINED THRUST INCREASE AND CLB WHEN AUTOFLT SYS ARMED TO FLY THE APCH.

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I WAS ON DUTY AS FO FOR FLT FROM DCA TO DTW. WE WERE CLRED TO INTERCEPT ILS 3R LOC IN DTW AT 3000 FT ON A 010 DEG HDG AND TOLD TO FLY 170 KTS UNTIL OM. OUR A319 HAD JUST CAPTURED THE 3000 FT ALT; APCH PUSH BUTTON WAS ARMED FOR THE APCH AND WE WERE APPROX 14 MI FROM THE RWY. AUTOPLT #1 WAS ACTIVATED WITH AUTOTHRUST ALSO ACTIVATED. APCH MODE WAS ACTIVATED AND SPD 170 KTS SELECTED. WITHIN 2 OR 3 SECONDS OF ARMING THE APCH; THE A319 THRUST WENT TO TOGA AND INITIATED A STEEP CLB. THE CAPT SURVEYED THE SIT; AND DECIDED TO DISENGAGE THE AUTOPLT AND AUTOTHRUST. WE HAD CLBED TO APPROX 4500 FT BEFORE TAKING CTL OF THE ACFT AND DSNDED BACK TO 3000 FT. ONCE ON THE GND WE MADE SEVERAL PHONE CALLS TO TRAINING DEPT. THE PEOPLE IN TRAINING THOUGHT THAT THIS WAS A PROB OF THE PAST. APPARENTLY THE A319 WILL DO EXACTLY WHAT I DESCRIBED WHEN THE ACFT IS MORE THAN 10 MI FROM THE RWY. IT SENSED A GS WELL ABOVE THE ACFT ALT; AND MADE INPUTS TO INTERCEPT. TRAINING THOUGHT THE SOFTWARE WAS CHANGED; AND SO THEY DO NOT EMPHASIZE THIS TYPE OF SCENARIO DURING TRAINING. A BULLETIN DESCRIBING THIS TO AIRBUS PLTS IS NEEDED AS WELL AS CHANGES TO THE SOFTWARE. SUPPLEMENTAL INFO FROM ACN 542335: AFTER TALKING TO OUR TECHNICAL SUPPORT PEOPLE; THEY INFORMED ME THAT THIS IS A KNOWN DEFECT IN A319'S AND THAT AIRBUS SUGGESTS THAT YOU NOT ARM THE ILS UNTIL NEAR THE OM.