A DC9-30 FREIGHTER GETS A CALL FROM ZAN THROUGH SIT FSS THAT THEY ARE OFF COURSE ON THEIR DSCNT ON V-431 INTO SITKA.

Narrative

AIRLINE FLT WAS ENRTE FROM JUNEAU; AK; TO SITKA; AK. RTE OF FLT WAS JUNEAU TWO DEP; SISTERS ISLAND TRANSITION; SSR VOR V-431 TO CLUCK INTXN; LDA DME RWY 11 TO SITKA ARPT. JUST PAST SSR VOR ON V-431 AT 16000 FT; ZAN CLRED US FOR THE LDA DME RWY 11 APCH TO SITKA AND ADVISED US TO SWITCH TO SITKA RADIO. AT THIS POINT WE DSNDED TO 8000 FT; THE MEA FOR THAT SEGMENT OF THE AIRWAY. AT 34 DME OFF SSR WE MADE THE TURN ON THE AIRWAY SWITCHING FROM #1 NAV TO THE #2 NAV; NOW ENRTE TO BKA VOR VIA BKA 327 DEG RADIAL. ESTABLISHED INBOUND TO BKA VOR WE BEGAN A DSCNT FROM 8000 FT TO 5000 FT WHICH IS THE MEA FOR THAT PORTION OF V-431. APPROX 35-40 DME FROM BKA AT 5500 FT ZAN (THROUGH SITKA RADIO) ADVISED US WE WERE L OF COURSE AND TO MAKE AN IMMEDIATE 50 DEG R TURN AND CLB TO 7000 FT AND CALL ZAN. WE COMPLIED WITH THE INSTRUCTIONS AND FLEW TO BKA VOR AND SHOT THE SAME APCH VIA 20 DME ARC. APCHING BKA WE WERE GIVEN A HEADING TO INTERCEPT THE 295 DEG RADIAL N OF BKA. AS WE APCHED THE 295 DEG RADIAL WE ASKED THE CTLR IF THEY SHOWED US JOINING THE RADIAL. NEEDLE CTRED USING THE #2 NAV SYS. THE CTLR SAID WE HADN'T REACHED THE RADIAL YET. USING #1 NAV SYS WE MADE AN UNEVENTFUL LNDG. AT ALL TIMES DURING FLT OUR ACFT INSTS SHOWED US TO BE ON THE AIRWAY. WE THOUGHT WE WERE RECEIVING A GOOD SIGNAL WITH THE #2 NAV SYS; HOWEVER; THE COURSE SIGNAL FLUCTUATED A COUPLE OF TIMES AND THE DME WENT OFF LINE A COUPLE OF TIMES BUT ONLY FOR A FEW SECONDS. UPON LNDG AT SITKA #2 DME WAS IN ERROR BY 2 MI FROM ARPT TO BKA AND FROM #1 NAV SYS. (#1 NAV SHOWED CORRECT) #2 NAV WAS WRITTEN UP AS BEING IN EXCESSIVE ERROR.