COMMUTER LTT LANDED IN WX REPORTED BELOW ARPT WX MINIMUMS FOR LNDG.

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COMPANY ADVISED WE WERE TO REPOSITION THE ACFT UNDER PT 91 TO OUR HDQ CITY. CAPT AND I LAUNCHED WITH OUR FLT ATTENDANT IN JUMP SEAT FOR THE 35 MIN FLT. UPON RECEIVING THE ATIS I MADE NOTE OF THE FACT TO THE CAPT THAT THE RVR WAS 1600; 800 LESS THAN THE REQUIRED 2400. CAPT WHO HAD LESS TIME IN TYPE (APPROX 150 HOURS TOTAL) THAN I; OPTED TO TRY THE APCH. THE AUTOPLT COUPLED UP AND FLEW THE APP WELL UNTIL THE OUTER MARKER WHERE WE LOST ONE RUDDER SYSTEM CAUSING THE A/C TO YAW CONTINUOUSLY. INSIDE THE OUTER MARKER TWR CLRD US TO LAND AND ADVISED RVR NOW 1300. I TOLD THE CAPT WE SHOULD MISS THE APCH AS TO AFOREMENTIONED ITEMS. HE STILL INSISTED ON FLYING THE APCH. I MADE THE STANDARD INSTRUMENT CALLS AS REQUESTED BY THE COMPANY. UPON REACHING DECISION HEIGHT I HAD ONLY A BRIEF GLIMPSE OF THE RABBIT BUT NOT THE APCH LIGHTING SYSTEM. I CALLED FOR MISSED APCH AND THE CAPT SAID HE HAD THE LIGHTS AND CONTINUED TO 100' ABOVE TOUCHDOWN ZONE WITH THE NON CAT 22 A/P 'ON'. I STILL HAD NO ALS IN SIGHT BUT DID GLIMPSE TWO RWY LIGHTS CAPT THEN DROPPED AIRPLANE ONTO RWY FROM ABOUT 50'. TWR WAS STILL REPORTING 1300 RVR AND ASKED FOR OUR FLT CONDITIONS AT DECISION HEIGHT AT WHICH TIME CAPT REPORTED TO TWR THAT WE HAD REQUIRED FLT VISIBILITY AT DH WHICH WAS TOTALLY UNTRUE. BAD JUDGEMENT BY A CAPT WITH A BIGGER EGO THAT EXPERIENCE RISKED MY SAFETY AND THE FLT ATTENDANTS BY HIS FEELING HE COULD LAND IN ANY TYPE OF VISIBILITY. IF CO-PLT IS NOT UTILIZED TO MAKE A JUDGEMENT AS TO WHETHER TO MISS THE APCH THEN ASK WHY IS ONE NEEDED?