B727-200 CREW HAD ERRONEOUS POS INDICATIONS WHILE ON VECTORS FOR THE ILS DME 09 APCH AT SVMI.

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ON APCH TO MIQ THE NIGHT OF TUE MAY WE WERE CLRED ON A 130 DEG HEADING TO INTERCEPT LOC FOR ILS 09 TO MIQ AT INITIAL ALTITUDE OF 2000 FT. FO WAS FLYING AND HAD ILS. MONITORING VOR 272 DEG RADIAL. ACFT WAS IN CLOUDS. VOR SHOWED ACFT STILL N OF 280 RADIAL-ILS NEEDLE STILL PEGGED TO THE R; BUT GS NEEDLE SHOWED ACFT BEGINNING TO GO ABOVE GS. AS VOR SHOWED ACFT STILL ON 280 RADIAL-ILS NEEDLE IMMEDIATELY SWUNG FULL SCALE TO THE L. BEGAN IMMEDIATE TURN TO L;BROKE OUT OF CLOUDS AND SAW THE ACFT WAS WELL TO R OF CENTERLINE OF RWY. CREW FELT THAT BOTH ILS AND VOR RADIAL INFO WAS UNRELIABLE BASED ON NEEDLE MOVEMENTS AND SUBSEQUENT POS OF ACFT. WE WERE ON THE VERGE OF GOING AROUND TO N WHEN WE BROKE OUT AND WERE ABLE TO LAND. IDENTIFIERS FOR BOTH ILS AND VOR WERE GOOD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE NO.2 NAV RECEIVER WAS ON THE LOC; WITH 096 IN THE COURSE WINDOW. AND THE NO. 1 NAV RECEIVER ON THE MIQ VOR WITH THE 272 RADIAL SELECTED. THE SO WAS THE FIRST TO NOTICE THE ANOMALY. THE CREW WAS ALSO MONITORING POS WITH THE GPS AND ACFT WX RADAR. THEY HAVE NO IDEA WHY THE PROB OCCURRED. NOTHING WAS WRONG WITH THE ACFT NAV SYSTEMS AND NO PROBS WERE RPTED WITH GND NAV AIDS. THE CREW FLEW INTO SVMI ALL MONTH AND HAD NO FURTHER PROBS.