FLT CREW OF A310 DSNDED WELL BELOW GLIDEPATH WHILE FLYING IAP WITH INOPERATIVE GLIDEPATH INDICATIONS. FATIGUE AND UNEXPECTED NAV INDICATION FAILURES ON PLANNED CAT III APCH IN VISUAL CONDITIONS CONTRIBUTED TO THE ERROR.

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LAST LEG OF LONG DUTY NIGHT DUE TO ARR DEP DELAYS FROM MEM DUE TO PASSING OF STORM. ACFT WAS NOT 'CAT II' SO WE BRIEFED A MONITORED CAT III APCH TO IND TO UPGRADE CAT STATUS WITH AN AUTOLNDG. CAPT MADE THE TKOF AND FLEW ACFT UNTIL BOD INTO IND. I TOOK THE AIRPLANE FOR THE DSCNT. DSCNT AND APCH CHKLISTS WERE COMPLETE; WE WERE ON THE LOC AND CLRED FOR THE APCH. WE WERE LATE IN NOTICING THE GS WAS NOT AVAILABLE AND USING A 3:1 PROFILE; WE KNEW WE WERE ABOVE THE GS. I CLICKED OFF THE AUTOPLT AND THE CAPT DIALED IN VERT SPD MODE AND TOLD ME TO START DOWN. THERE WAS NO PAPI OR VASI FOR THIS RWY. TWR CLRED US TO LAND AND ASKED 'IF WE CAN MAKE IT.' THE CAPT SAID; 'YEAH; NO PROB.' WE WERE FULLY CONFIGURED AND CHKLISTS WERE COMPLETED AND THE RWY WAS IN SIGHT. AS WE DSNDED THROUGH 1200 FT AGL AT 4 MILES ON THE PROFILE NOW; I ASKED FOR 700 FT VERT SPD FOR THE FLT DIRECTOR TO KEEP ON THE PROFILE. I SPENT TOO MUCH TIME INSIDE AND WAS SLOW IN BREAKING THE RATE OF DSCNT; AND BY 2 MILES I HAD GOTTEN LOW. WE WERE SLOWING THE RATE OF DSCNT AT THE TIME AND REALIZED WE WERE BELOW THE PROFILE. ABOUT TWO SECONDS LATER; TWR SAID WE HAVE A LOW ALT ALERT. WE ACKNOWLEDGED THEM; GOT BACK ON PROFILE AND LANDED UNEVENTFULLY. THIS WAS MY FIRST TRIP AFTER IOE. THE APCH STARTED AS A FULLY COUPLED CAT III WITH THE CAPT TAKING THE ACFT AND DOING THE AUTOLAND. WHEN IT TURNED INTO A VISUAL APCH WITH NO GLIDEPATH INFO; I WAS SLOW TO TRANSITION TO A VISUAL APCH. ONCE THE CAPT DIALED IN A VERT SPD ON THE FCP; IT LOOKED LIKE MY FLT DIRECTOR WAS CORRECT AND I FLEW IT WITHOUT COMING OUTSIDE ENOUGH TO SEE MY PROGRESS. THERE'S NO EXCUSE FOR MY SLOW TRANSITION TO A VISUAL APCH; BUT I THINK THE FATIGUE PLAYED A BIG FACTOR. ALSO I EXPECTED TO DO A COUPLED APCH; NOT A VISUAL WITH NO GLIDEPATH; AND I EXPECTED THE CAPT TO DO THE LNDG. WE DISCUSSED ALL OF THIS AFTERWARDS AND REALIZED THE MANY ERRORS AND BETTER WAYS OF DEALING WITH THE SIT.