AN INCORRECT DME MODE WAS SELECTED BY THE PF; WHICH PLACED THE ACFT 10 MI AWAY FROM INTENDED POS ON AN IAP.

Narrative

INBOUND TO SITKA; THE LDA DME RWY 11 APCH WAS FULLY BRIEFED. THIS WAS THE FIRST TIME THE CREW HAD FLOWN TOGETHER AND THE FIRST TIME IN THIS PARTICULAR ACFT FOR THE CAPT. CAPT STARTED TO TURN ON 20 DME ARC AT 23 DME AT 250 KTS. COPLT ASKED AT THAT TIME IF IT WAS A 30 DME ARC (TRIAL BALLOON). ESTABLISHED ON THE ARC THE COPLT SAID 'YOU ARE STILL ON VLF NAV ON THE DME.' THIS PUT US 8 MI OUTSIDE THE ARC. WE IMMEDIATELY STOPPED OUR DSCNT AND TURNED TOWARD THE ORIGINAL INBOUND RADIAL. SINCE WE WERE ON TOP WE MAINTAINED 5000 FT WHICH WAS THE LAST ASSIGNED ALT 'UNTIL INTERCEPTING A PUBLISHED PORTION OF THE APCH.' THE REST OF THE APCH WAS NORMAL. AS A CAPT I WAS TOO NONCHALANT ABOUT THE DIFFERENCES IN AVIONICS PACKAGES BTWN THIS ACFT AND THE ACFT NORMALLY FLOWN. WHEN THE COPLT (WHO HAD NOT FLOWN THIS RTE BEFORE) QUERIED ME AS I TURNED ON THE ARC I TOOK IT AS A QUESTION ON HIS PART; RATHER THAN A QUESTION OF MY EXECUTION OF THE PROC. ON A FLT WHICH HAD BUILT IN CONTRIBUTING FACTORS; I DID NOT BRING ENOUGH PARANOIA ALONG.