A319 FO REPORTS ANOMALOUS FMGC OPERATION DURING TWO CONSECUTIVE APPROACHES TO TWO DIFFERENT ARPTS.

Narrative

WE WERE ON A L BASE CLRED FOR THE VISUAL APCH INTO LAS RWY 25L OUTSIDE THE FAF AND JUST A LITTLE HIGH ON THE PROFILE. DSNDING AND TURNING FROM BASE TO FINAL; I HAD THE AIRPLANE CONFIGURED WITH FLAPS 2 DEGS AND GEAR DOWN. I THEN SELECTED MANAGED SPD; ARMED THE APCH; AND ENGAGED AUTOPLT #1 AS IS NORMAL FOR AN ILS APCH (AUTOPLT #2 WAS ALREADY ENGAGED). WE HAD PLENTY OF ROOM WITH ABOUT A 20 DEG INTERCEPT FOR THE FINAL APCH COURSE. EVERYTHING WAS LOOKING GOOD AND I WAS JUST SHALLOWING UP THE DSCNT BY REDUCING THE SELECTED VERT SPD ON THE FCU TO MATCH THE GS RAW DATA. I THEN NOTICED THAT THE AIRPLANE STARTED ADDING PWR AND ACCELERATING. I MADE A COMMENT AS TO WHY THAT WAS HAPPENING (THE APCH HAD BEEN ACTIVATED AND CONFIRMED DURING DOWNWIND LEG). THEN THE CAPT NOTICED THAT THE AIRPLANE WAS NOT INTERCEPTING THE LOC AS WE WERE FLYING THROUGH IT. I QUICKLY DISCONNECTED THE AUTOPLTS USING THE SIDE STICK BUTTON AND MANEUVERED THE AIRPLANE BACK TOWARD THE LOC. I ALSO RESET THE AUTOTHRUST AS THE SPD HAD ACCELERATED TO ABOUT 180 KTS. APCH MODE WAS STILL INDICATING ARMED WITH CORRECT FMS INDICATIONS. I CONTINUED TO HAND FLY THE APCH. WE WERE SLIGHTLY OVER 10 KTS FAST WITH THE AIRPLANE FULLY CONFIGURED AT THE 1000 FT GATE. A NORMAL LNDG FOLLOWED. WHILE APCHING PHX ON OUR NEXT LEG; SAME AIRPLANE; SIMILAR CONDITIONS WITH A 20-25 DEG L INTERCEPT FOR THE ILS RWY 8. THE CAPT FLYING THIS TIME; TRIED TO REPLICATE THE EVENT EXCEPT HE HAD SELECTED SPD ON THE FCU (150 KTS). WITH THE AIRPLANE IN THE SAME CONFIGN AS ABOVE (AUTOPLT #2 SELECTED BEFORE ARMING THE APCH); HE ARMED THE APCH AND THEN SELECTED AUTOPLT #1. AT THIS TIME THE AIRPLANE DROPPED THE FMS ANNUNCIATIONS THAT INDICATE AN ARMED APCH (EVEN THOUGH THE APCH BUTTON LIGHT REMAINED ILLUMINATED) AND THE SPD WENT FROM MANUALLY SELECTED (BLUE INDICATION ON PFD) TO MANAGED BY ITSELF (MAGENTA ON PFD) AND STARTED ACCELERATING TOWARD 170 KTS. THE CAPT THEN DESELECTED AUTOPLT #1 AND THINGS RETURNED TO NORMAL. A NORMAL APCH AND LNDG FOLLOWED. LOOKS LIKE A SOFTWARE BUG TO ME. FLT CREW SUGGESTIONS/NARRATIVE: WHERE DO I BEGIN. I KEEP WRITING RPTS ON THIS CRAPPY SOFTWARE BUT NOTHING EVER GETS FIXED RIGHT OR IN A TIMELY MANNER. THE PLTS KEEP COMPENSATING FOR THE EXTRA BURDEN IMPOSED BY BAD SOFTWARE AND BAD PROCS.