AFTER THE PLT OF A BEECH BARON; BE58; WAS CLRED FOR A VOR APCH; HE WAS GIVEN VECTORS TO CORRECT HIS HEADING AND TRACK SINCE HE WAS R OF COURSE IN ADDITION; RPTR DSNDED BELOW THE PUBLISHED STEP DOWN ALT CAUSING APCH CTLR TO GIVE A LOW ALT ALERT.

Narrative

I WAS ENRTE ON AN IFR FLT PLAN FROM LAS CRUCES; NM (LRU) TO SANTA MONICA; CA (SMO). I WAS FLYING V186 FROM THE PARADISE VOR (PDZ) TO DARTS INTXN; WHICH IS THE INITIAL APCH FIX FOR THE VOR-A RWY 21 APCH TO SMO. I WAS USING THE GPS COUPLED TO THE HSI/CDI FOR NAV. I WAS HAVING TO FLY A 245 DEG HDG OR 30 DEGS L OF MY 275 DEG COURSE HDG FOR V186 IN ORDER TO STAY ON THE FLT PATH. I ATTRIBUTED THE REQUIRED CORRECTION TO A FORECAST XWIND FROM THE S; HOWEVER; THE AMOUNT OF CORRECTION I WAS HAVING TO MAINTAIN WAS MORE THAN THE FORECAST WINDS. UPON APCHING DARTS INTXN SOCAL APCH GAVE ME AN ASSIGNED 245 DEG HDG TO INTERCEPT THE APCH COURSE; WHICH I DID. HE ALSO CLRED ME FOR THE APCH AND INSTRUCTED ME TO MAINTAIN 4000 FT UNTIL ESTABLISHED. AT THIS TIME I ALSO SWITCHED TO THE NAV #1 FOR NAV. THE NEEDLE CTRED AND I TURNED INBOUND TO THE APCH COURSE OF 212 DEGS AND STARTED MY DSCNT FROM 4000 FT MSL TO 2600 FT MSL. SOCAL APCH THEN ADVISED ME THAT I WAS R OF COURSE. I EXPLAINED THAT I WAS SHOWING THE NEEDLE CTRED. THEY THEN ADVISED ME TO TURN 30 DEGS L WHICH I DID TO A 182 DEG HDG. SOCAL APCH THEN SAID I WAS STILL R OF COURSE. AT ABOUT THIS TIME I REALIZED; AS DID SOCAL APCH; THAT I HAD A DIRECTIONAL GYROSCOPE PROB THAT WAS REFLECTING TO ME 30 DEGS L OF MY ACTUAL HEADING; WHICH HE WAS SEEING ON HIS SCREEN. I THEN NOTICED THAT MY COMPASS SLAVE UNIT SHOWED A FULL DEFLECTION ERROR EVEN THOUGH IT WAS IN THE SLAVE MODE. SOCAL APCH THEN ADVISED ME TO TURN FURTHER TO THE L. THEY THEN ADVISED ME I HAD INTERCEPTED THE APCH COURSE AND TO MAINTAIN A 182 DEG HDG ON MY DIRECTIONAL GYROSCOPE CARD WHICH WAS THE REQUIRED CORRECTION NECESSARY TO STAY ON THE APCH COURSE. I SHOULD HAVE AT THIS TIME RELIED ON THE COMPASS TO CONFIRM MY BEING ON COURSE BUT IN THE RUSH OF THINGS I ASKED SOCAL APCH TO CONTINUE TO GIVE ME VECTORS IF NEEDED TO STAY ON THE APCH COURSE. DURING THE SAME TIME THAT I; ALONG WITH HELP FROM SOCAL APCH; WAS DIAGNOSING THE COURSE DEV PROB; SOCAL APCH ISSUED AN ALT ALERT AS I HAD DSNDED 200 FT BELOW THE REQUIRED ALT OF 2600 FT MSL AND REQUESTED THAT I IMMEDIATELY CLB WHICH I DID EVEN THOUGH MY CLB WAS SLOWED BY MY HAVING ALREADY DROPPED MY LNDG GEAR AND APCH FLAPS. SOCAL APCH THEN ADVISED ME THAT I WAS AT MY NEXT STEP-DOWN FIX AND I DSNDED TO 1100 FT MSL. I WAS ALSO INSTRUCTED TO GO TO THE TWR FREQ; WHICH I DID. I BROKE OUT OF THE LAYER OF CLOUDS AT APPROX 1700 FT MSL AND WAS CLRED TO LAND.