AN A320 IN AUTOFLT ATTEMPTED AN AUTOPLT COUPLED APCH. UPON SELECTING THE APCH MODE SINCE THE ACFT INCREASE THRUST AND CLBED RATHER THAN FLY THE APCH.

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THE ACFT WAS BEING FLOWN BY THE CAPT AND WAS ON VECTORS FOR THE RWY 9R LOC AT PHL. THE ACFT WAS LEVEL AT 3000 FT MSL; IN IMC; 190 KTS; FLAPS 1 DEG. ALL FMGS AUTOMATION WAS IN USE: AUTOPLT #1 ENGAGED; AUTOTHROTTLE ACTIVE; FLT DIRECTOR #1 AND #2 ON; LOC ARMED; HDG SELECTED FOR THE VECTOR TO THE LOC. JUST AS THE ACFT CAPTURED THE LOC; ATC ISSUED THE ILS RWY 9R APCH CLRNC; AT WHICH TIME THE CAPT PUSHED THE APCH BUTTON AND SELECTED AUTOPLT #2 PER COMPANY PROC (IE; AUTOPLT #1 CTLING; AUTOPLT #2 ARMED). ALL FMA ANNUNCIATIONS WERE CORRECT. IMMEDIATELY UPON PUSHING THE APCH AND AUTOPLT #2 BUTTONS (THE BUTTONS WERE PUSHED WITHIN 1-2 SECONDS OF EACH OTHER); THE ACFT PITCHED UP ABRUPTLY AND THE AUTOTHROTTLE SYS COMMANDED A SIGNIFICANT INCREASE IN THRUST; BUT DID NOT GO TO TOGA. THE CAPT DISCONNECTED THE AUTOPLT AND RECAPTURED THE ALT AND LOC COURSE. THE ACFT HAD CLBED TO 3600 FT. AUTOTHROTTLE REMAINED ENGAGED THROUGHOUT THE EXCURSION. THRUST WAS REDUCED BY THE AUTOTHROTTLE SYS AS THE CAPT BEGAN A DSCNT TO THE ASSIGNED ALT. DURING THE UNCOMMANDED CLB; THE FMA CONTINUED TO SHOW ALT GREEN; LOC GREEN AND GS BLUE. AUTOTHROTTLE CONTINUED TO ANNUNCIATE SPD GREEN. THE CAPT RE-ENGAGED THE AUTOPLT AND THE LNDG WAS COMPLETED WITHOUT FURTHER ANOMALIES. ON THE GND IN PHL; AN AIRBUS TECHNICAL REPRESENTATIVE EXAMINED THE AVAILABLE STORED SYS RPTS AND FOUND NO DISCREPANCIES IN THE ACFT SYS. HE ATTRIBUTED THE FAULT TO THE CAPT'S 'PROCS.' IT IS MY OBSERVATION THAT THE CAPT'S PROCS WERE TIMELY AND CORRECT AND CONSISTENT WITH PUBLISHED COMPANY PROCS. ALTHOUGH 3 CHANGES OCCURRED ALMOST SIMULTANEOUSLY WITH THE UNCOMMANDED CLB (LOC CAPTURE; AUTOPLT #2 ARMED AND APCH ENGAGED) I BELIEVE THE CLB BEGAN AS AUTOPLT #2 WAS ARMED. FOR WHATEVER REASON; I BELIEVE AUTOPLT #2 WAS COMMANDING OPEN CL; EVEN THOUGH THE FMA DID NOT INDICATE THIS; NOR WAS THE FCU SET TO A HIGHER ALT THAN 3000 FT MSL. THE AUTOTHROTTLE SYS RESPONDED AS IF OPEN CL HAD BEEN COMMANDED AND INCREASED THRUST DURING THE CLB; THEN DECREASED THRUST AS THE CAPT DSNDED TO 3000 FT.