A320 CAPT FORGOT TO ACTIVATE THE APCH PHASE BEFORE ACTIVATING THE MANAGED SPD AUTOPLT FEATURE DURING A VISUAL APCH RESULTING IN THE ACFT AUTOMATICALLY GOING TO CLB THRUST.

Narrative

THIS FLT WAS SCHEDULED TO BOI. THERE WAS AN FAA INSPECTOR ON THE JUMP SEAT CONDUCTING AN ENRTE CHK. BOISE WAS CONDUCTING VISUAL APCHS TO RWY 28R&L. THE DSCNT AND APCH WENT FINE UNTIL I REQUESTED THE FO TO SELECT MANAGED SPD. WE BOTH SUDDENLY REALIZED WE HAD FORGOTTEN TO ACTIVATE AND CONFIRM THE APCH PHASE BECAUSE THE COMMANDED SPD WENT TO GREEN DOT (210 KTS) AND AUTOTHROTTLE TO CLB THRUST. WE IMMEDIATELY CORRECTED; I CLOSED THE THRUST LEVERS (NOW MANUAL THRUST); BUT NOW I HAD A GREAT DEAL OF EXCESS ENERGY TO DISSIPATE. I ALMOST WENT AROUND; BUT MADE A COUPLE OF S-TURNS ON THE FINAL APCH WITH TWR'S CONCURRENCE. I WAS STABILIZED BY 500 FT AGL AND MADE A SMOOTH LNDG IN THE TOUCHDOWN ZONE; ON SPD. I DON'T BELIEVE ANY VIOLATIONS OCCURRED; BUT THE INSPECTOR WAS NOT IMPRESSED! I HAVE FLOWN THIS ACFT ALMOST 34 YRS AND THIS IS THE FIRST TIME I HAVE BEEN BITTEN BY THIS MISTAKE. WHY WE FORGOT TO ACTIVATE THE APCH PHASE I CAN'T EXPLAIN. I WOULD HATE TO SAY WE WERE DISTR BY BEING OBSERVED; BUT MAYBE. I DO BELIEVE; HOWEVER; THAT THIS DESIGN OF THE SOFTWARE IS VERY POOR AND I KNOW OF MANY AIRBUS PLTS WHO HAVE EXPERIENCED THIS. I DOUBT I WILL FORGET AGAIN.