Narrative:

Clear night, IFR flight plan from lansing, mi, to lebanon, nh. Leb reporting a layer at 4100 ft and winds variable around 4 KTS. There were 2 aircraft ahead for the approach, the first (small single engine) flew the VOR runway 25 and reported picking up light/moderate rime on the descent. The second, a commuter, flew the ILS runway 18 and reported negligible icing as he descended through the thin layer. We chose to fly the ILS and were cleared to burgr to hold at 6000 ft until cleared for the approach. We had had some problems earlier that day with our #1 navigation and had had it looked at in lansing. It seemed to be working on the flight back to leb but as we entered the hold, the navigation began to be somewhat erratic. We were cleared after a very short time to begin the ILS and we left the holding thinking we were flying north away from burgr to intercept the localizer and track it outbound. I noted that we were moving away from burgr but no intercept of the localizer track. I also noted a discrepancy between my #1 and #2 navs as well as the compass and GPS. I halted my descent at 4100 ft and notified the tower we were going missed. The tower asked whether we realized that we were approximately 10 mi southeast of the VOR. We, of course, did not. We switched to center and got a vector to return to the VOR using our #2 navigation. We climbed to 5000 ft, popped the ice we had picked up and flew the VOR runway 25, landing without further difficulty. In retrospect, it is clear that the #1 navigation went bad soon after I entered the hold but it did not pick it up until I had flown some distance away from burgr. I had set my second navigation to the ILS as a check and as soon as I picked up a discrepancy that was it for the approach. It was particularly strange since a lear 35 had been lost at leb only a few days before and it had last been reported on a similar track southeast of the airport paralleling the ILS. The navigation was checked and is now ok. This reinforces my requirement to use the second navigation to confirm the track of the first. Any discrepancy is cause for going missed, getting high and sorting it out away from the granite. Both the tower and ZBW were extremely helpful during both approachs. Center, especially, was sensitive to the potential icing problem and moved me through the layer quickly.

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Original NASA ASRS Text

Title: PA60-602P ACFT #1 NAV SYS BECAME ERRATIC WHILE RPTR WAS IN HOLDING PATTERN AND WHEN DEPARTING HOLDING RPTR NOTICED DISCREPANCY BTWN #1 AND #2 NAVS. TWR AND CTR ADVISED RPTR THAT HE WAS 10 MI OFF COURSE AND PROVIDED VECTORS FOR APCH.

Narrative: CLR NIGHT, IFR FLT PLAN FROM LANSING, MI, TO LEBANON, NH. LEB RPTING A LAYER AT 4100 FT AND WINDS VARIABLE AROUND 4 KTS. THERE WERE 2 ACFT AHEAD FOR THE APCH, THE FIRST (SMALL SINGLE ENG) FLEW THE VOR RWY 25 AND RPTED PICKING UP LIGHT/MODERATE RIME ON THE DSCNT. THE SECOND, A COMMUTER, FLEW THE ILS RWY 18 AND RPTED NEGLIGIBLE ICING AS HE DSNDED THROUGH THE THIN LAYER. WE CHOSE TO FLY THE ILS AND WERE CLRED TO BURGR TO HOLD AT 6000 FT UNTIL CLRED FOR THE APCH. WE HAD HAD SOME PROBS EARLIER THAT DAY WITH OUR #1 NAV AND HAD HAD IT LOOKED AT IN LANSING. IT SEEMED TO BE WORKING ON THE FLT BACK TO LEB BUT AS WE ENTERED THE HOLD, THE NAV BEGAN TO BE SOMEWHAT ERRATIC. WE WERE CLRED AFTER A VERY SHORT TIME TO BEGIN THE ILS AND WE LEFT THE HOLDING THINKING WE WERE FLYING N AWAY FROM BURGR TO INTERCEPT THE LOC AND TRACK IT OUTBOUND. I NOTED THAT WE WERE MOVING AWAY FROM BURGR BUT NO INTERCEPT OF THE LOC TRACK. I ALSO NOTED A DISCREPANCY BTWN MY #1 AND #2 NAVS AS WELL AS THE COMPASS AND GPS. I HALTED MY DSCNT AT 4100 FT AND NOTIFIED THE TWR WE WERE GOING MISSED. THE TWR ASKED WHETHER WE REALIZED THAT WE WERE APPROX 10 MI SE OF THE VOR. WE, OF COURSE, DID NOT. WE SWITCHED TO CTR AND GOT A VECTOR TO RETURN TO THE VOR USING OUR #2 NAV. WE CLBED TO 5000 FT, POPPED THE ICE WE HAD PICKED UP AND FLEW THE VOR RWY 25, LNDG WITHOUT FURTHER DIFFICULTY. IN RETROSPECT, IT IS CLR THAT THE #1 NAV WENT BAD SOON AFTER I ENTERED THE HOLD BUT IT DID NOT PICK IT UP UNTIL I HAD FLOWN SOME DISTANCE AWAY FROM BURGR. I HAD SET MY SECOND NAV TO THE ILS AS A CHK AND AS SOON AS I PICKED UP A DISCREPANCY THAT WAS IT FOR THE APCH. IT WAS PARTICULARLY STRANGE SINCE A LEAR 35 HAD BEEN LOST AT LEB ONLY A FEW DAYS BEFORE AND IT HAD LAST BEEN RPTED ON A SIMILAR TRACK SE OF THE ARPT PARALLELING THE ILS. THE NAV WAS CHKED AND IS NOW OK. THIS REINFORCES MY REQUIREMENT TO USE THE SECOND NAV TO CONFIRM THE TRACK OF THE FIRST. ANY DISCREPANCY IS CAUSE FOR GOING MISSED, GETTING HIGH AND SORTING IT OUT AWAY FROM THE GRANITE. BOTH THE TWR AND ZBW WERE EXTREMELY HELPFUL DURING BOTH APCHS. CTR, ESPECIALLY, WAS SENSITIVE TO THE POTENTIAL ICING PROB AND MOVED ME THROUGH THE LAYER QUICKLY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.