A MIL HELI CREW; ENRTE AT 6000 FT; DEVIATED FROM COURSE WHEN THEIR NAV DISPLAY EQUIP WAS MISINTERPED.

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THIS EVENT OCCURRED ON MAR/XA/02 WHILE ACTING AS PIC IN A UH60 BLACKHAWK GOING FROM LBE-LCK. WE ORIGINALLY HAD FILED A VFR FLT PLAN; BUT WHILE SITTING AT IDLE ON THE RAMP AT LBE WE HAD TO FILE AN IFR FLT PLAN DUE TO SNOW SQUALLS. WHEN WE DEPARTED LBE WE WERE GIVEN RADAR VECTORS TO INTERCEPT V12 ON A HDG OF 290 DEGS AND CLB TO 6000 FT. WE TUNED AND IDENTED THE AGC VOR AND FLEW TO INTERCEPT. AS WE CONTINUED THE CDI ON MY HSI KEPT WAVERING BACK AND FORTH; SO I ELECTED TO FLY THE #1 NEEDLE ON MY RMI. WHEN THE #1 NEEDLE SHOWED A 277 DEG RADIAL; I MAINTAINED THE COURSE; BUT THE CDI WAS STILL WAVERING. AFTER SOME TIME PAST THE AGC VOR; ATC ASKED US IF WE WERE STILL ON AN ASSIGNED HDG. WE TOLD HIM NO; WE WERE ON V12. HE TOLD US WE WERE APPROX 6 MI S OF COURSE AND ASKED US OUR HDG. WE TOLD HIM IT WAS 277 DEGS; AND HE SAID THAT WAS OK. AT SOME POINT WE PUT IN THE CTW VOR TO SEE IF THERE WAS A PROB WITH OUR EQUIP OR THE VOR. WE SEEMED TO GET A BETTER SIGNAL AND BEGAN CORRECTING TO THE N. AT THIS POINT I THINK WE WERE ONLY ABOUT 20 MI W OF AGC VOR. WE WERE THEN TOLD WE WERE ABOUT 1/2 MI S OF COURSE. FINALLY SOMEWHERE IN THE VICINITY OF HLG VOR; WE WERE ABLE TO GET ON COURSE AND CONTINUE. AFTER GETTING HOME; I WAS TRYING TO FIGURE OUT WHAT HAPPENED AND WHY WE WERE SO FAR OFF COURSE; EVEN THOUGH THE #1 NEEDLE SHOWED ME ON COURSE. AFTER REFERRING TO THE DASH 10 POH I SAW WHAT I DID. I SITE 4 THINGS THAT CAUSED MY CONFUSION ENRTE: 1) LACK OF COMPLETE KNOWLEDGE OF THE COMMAND INST SYS IN THE UH60; 2) LACK OF EXPERIENCE OVERALL IN THE UH60; 3) A HABIT XFER; AND 4) POSSIBLY A WEAK SIGNAL FROM AGC VOR. OUR UNIT HAS RECENTLY TRANSITIONED TO THE UH60 BLACKHAWK FROM THE UH-1H HUEY. WHAT I HAD DONE WAS FLY THE RMI LIKE IN A HUEY; OR ANY OTHER ACFT FOR THAT MATTER (IE; #1 NEEDLE VOR; #2 NEEDLE ADF). IN THE HUEY WE'D USE THE #1 NEEDLE FOR SITUATIONAL AWARENESS OF WHERE THE COURSE WAS AND THEN TRANSITION TO THE COURSE INDICATOR IN WHICH THE RADIAL WAS SET WITH THE OBS. UNFORTUNATELY; IN THE UH60; THE #1 NEEDLE IS ALWAYS SET TO THE GPS/DOPPLER; THE #2 NEEDLE CAN BE SET TO EITHER THE VOR OR ADF. IN SUMMARY; BECAUSE OF A WEAK SIGNAL FROM AGC VOR; I ELECTED TO FLY THE RMI #1 NEEDLE (GPS/DOPPLER) AND ALTHOUGH I WAS FLYING THE 277 DEG RADIAL; IT WAS TO SOME OTHER POINT IN THE GPS (POSSIBLY CTW OR APE) WHICH CAUSED US NEVER TO REALLY INTERCEPT V12. WHAT IT HAD DONE WAS CAUSE US TO PARALLEL IT S OF COURSE. WHAT I SHOULD HAVE DONE WAS FOLLOW THE #2 NEEDLE WHICH WAS SET TO VOR MODE.