THE RPTR AS COPLT HAD TO ASSIST THE CAPT TO HAND FLY THE IAP ILS AND PROMPT A GAR AT MINIMUMS WHEN LOSING SIGHT OF THE RWY. THE RPTR STATED THE CAPT WAS OVER CORRECTING TO ACHIEVE ALIGNMENT WITH THE RWY AND CHASING THE APCH LIGHTS BELOW MINIMUMS. THE RPTR NOTED THAT MINIMUM APCHS SHOULD BE NORMALLY HAND FLOWN TO GAIN PROFICIENCY BUT THE CAPT FELT THAT MINIMUM APCHS SHOULD BE NORMALLY DONE ON THE AUTOPLT WHEN AVAILABLE.

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WE DEPARTED BOS ABOUT XA00 LCL PROCEEDED TO MTN. ON APCH NOTED THE CEILING AND VISIBILITY GOING DOWN. WE WERE CLRED FOR ILS RWY 33. CAPT PROGRAMMED AUTOPLT. AUTOPLT WOULDN'T COUPLE. CAPT BECAME OBSESSED WITH AUTOPLT. I SUGGESTED HE HAND FLY. WE DSNDED TO DECISION HT; SAW REIL. CAPT SAW REIL; WE WERE SLIGHTLY L OF CTR; HE THEN BANKED AND TRIED TO LINE UP ON REIL; I CALLED TO HIM AT DECISION HT AND WHEN WE LOST RWY CALLED MISSED. HE SAT AND DID NOTHING THEN REACTED TO MY CALL. IT APPEARED HE WAS TRYING TO LINE UP ON REIL AS IF IT WAS A RABBIT. THIS RESULTS IN A PERPENDICULAR APCH AND A 90 DEG HDG CHANGE WHICH IS WHAT HE WAS DOING. WE PROCEEDED TO PHL AND RETURNED TO MTN. ON APCH BRIEFING I NOW MAKE A POINT OF REVIEWING LIGHTING SYS AND WHAT THEY LOOK LIKE TO PF. I ALSO WILL NOTE THAT THIS PARTICULAR PLT FEELS THAT ALL MINIMUM APCHS SHOULD BE DONE AUTOPLT ONLY. HIS WORST FEARS CAME TRUE WHEN THE COUPLER FAILED. MY OPINION HAS ALWAYS BEEN TO SHOOT THE ILS MANUALLY ON ANY RWY IF IT HAS ONE TO MINIMUMS AND BE ABLE TO FLY BETTER THAN THE AUTOPLT AND USE THE COUPLER WHEN TIRED OR TO ASSURE SYS WORKS. RELYING ON AUTOPLTS IS DANGEROUS AND WHEN THEY FAIL A PLT WHO RELIES ON THE AUTOPLT IS LEFT WITH LESS THAN OPTIMAL SKILLS TO COMPLETE THE APCH; AS WAS DISPLAYED BY THIS INCIDENT.