A PA28 PLT FLYING ILS APCH TO RDU MIS-PROGRAMS HIS NEW GPS NAV SYSTEM AND INTERCEPTS WRONG RWY LOC.

Narrative

I WAS RETURNING FROM PRACTICE APCHES AND HOLDS AT HRJ AND WAS BEING VECTORED TO THE ILS RWY 5R. THE PLANE IS EQUIPPED WITH A NEW GNS480 AND A NAV/COM. I INITIALLY LOADED THE LOC FREQ INTO THE NAV2 RADIO AND IDENTIFIED THE MORSE CODE WHILE ON A 320 DEG VECTOR AT 3000 FT. RDU WAS SET AS THE DEST ALREADY. I WAS SWITCHED TO THE FINAL CTLR AND GIVEN A 310 HDG. I THEN WENT BACK TO SET UP THE GPS AND LOADED THE ILS RWY 5L (VECTORS) APCH BY MISTAKE. I SET THE BARO PRESSURE AND LET THE GPS AUTOLOAD THE LOC FREQ INTO THE NAV1. I NOTICED THE 109 FREQ AND FELT EVERYTHING WAS ALRIGHT -- BUT I DID NOT NOTICE IT WAS 109.1 (RWY 5L'S LOC INSTEAD OF THE 109.5 LOC FREQ OF RWY 5R). IN MY MIND AT THIS POINT; I FELT VERY SURE OF MYSELF BECAUSE THE NEW GPS PROVIDES A LOT OF HELP. I WAS CLRED FOR THE APCH ON A 030 DEG HDG. ON THAT HDG; I WAITED FOR THE LOC TO COME ALIVE AND FOR THE VOICE ANNUNCIATOR TO ANNOUNCE 'LOCALIZER ALIVE.' WHEN THE LOC WAS ALIVE THE GPS AUTOSWITCHED TO LOC CDI (AND ANNOUNCED THIS); I TURNED ON COURSE AND WAS IMMEDIATELY CALLED BY THE CTLR WHO ANNOUNCED THAT I HAD MISSED THE LOC. I WAS REALLY CONFUSED. I TURNED BACK TO THE RIGHT AND LOOKED DOWN AT BOTH INDICATORS. IT WAS OBVIOUS SOMETHING WAS WRONG BUT I WAS NOT SURE WHAT JUST YET -- I JUST KNEW THAT THE CDI'S WERE INDICATING DIFFERENTLY. I KNEW I HAD LISTENED TO THE ID ON THE NAV2 SO I FOLLOWED THE INDICATOR AND TRACKED THE LOCALIZER. I WAS REALLY UPSET AND CONFUSED; AND WHEN I TRACKED THE LOC CORRECTLY FOR RWY 5R; I THEN NOTICED THAT THE NAV2 GLIDESCOPE INDICATED LOWER THAN THE NAV1. I DID NOT WAIT -- I IMMEDIATELY STARTED A 500 FPM DSCNT AND LOOKED BACK AT THE NAV2 HEAD -- IT WAS CENTERED. THEN THE CTLR CALLED BACK AND SAID I WAS LOW -- I SHOULD BE AT 2400 FT. I IMMEDIATELY CLBED BACK UP AND AS I CROSSED 2300 FT; THE GLIDESCOPE INDICATOR JUMPED UP AND DOWN FROM THE TOP TO THE CENTER OF THE INSTRUMENT -- IT HAD JUST COME INTO RANGE AND WAS INDICATING A CLB. ONCE ESTABLISHED ON THE GLIDESCOPE; I TRACKED THE ILS SOLIDLY WITH NO FURTHER EVENTS. THERE ARE A FEW LESSONS. FIRST; YOU CAN NEVER BE TOO FAMILIAR WITH THE GPS. IT IS A GREAT TOOL BUT ONLY IF IT IS PROGRAMMED CORRECTLY. I SHOULD HAVE REVIEWED THE APCH FIXES IN THE GPS FOR THE RWY 5R APCH TO MAKE SURE THAT THEY MATCHED THE PLATE IN FRONT OF ME AND THAT I HAD THE CORRECT APCH LOADED. SECOND; YOU MUST CHECK THE ID FOR THE LOC; EVEN IF YOU THINK THE GPS AUTO SELECTED THE FREQ CORRECTLY. YOU MIGHT CATCH YOUR OWN MISTAKE. THIRD; NEVER BE TOO HASTY TO DSND ON THE GLIDESCOPE. CHK AND RECHK YOUR POSITION RELATIVE TO THE FAF AND THE FAF CROSSING ALT BEFORE DSNDING ANY FURTHER. I'VE DECIDED TO ADD A FEW THINGS TO MY ILS CHKLIST. FIRST; IT IS GOOD TO SET UP ALL THE EQUIP IN ORDER TO HAVE A LIVE BACKUP AND REDUNDANCY CHK; BUT IT IS EQUALLY IMPORTANT TO RECHK AND IDENTIFY ALL THE EQUIP IS ON THE RIGHT APCH AND FREQ WITH THE ID'S. SECOND; I AM INCLINED TO WAIT ON A SLIGHT DOWN INDICATION ON THE GS BEFORE COMMENCING A DSCNT. THIS WOULD PRECLUDE ANY POSSIBILITY OF DSNDING WITH THE GS FLAGGED. YES; FAF CROSSING ALTS SHOULD ALSO PREVENT THIS PROVIDED THAT YOU ARE AHEAD; AND NOT BEHIND THE AIRPLANE AS DID HAPPEN HERE. THIRD; IF I SHOULD EVER GET INTO A SITUATION WITH CONTRADICTORY INDICATIONS; I WILL TRY TO ABORT THE APCH AND GET THINGS STRAIGHTENED OUT RATHER THAN TRYING TO FIX THEM (SINGLE PLT IFR) ON AN APCH.