Narrative:

Cleared by ZMP direct fgt VOR, with pilot's discretion to cross 15 DME south at or below 15000' to maintain 10000'. Descent was initiated at 65 DME with the autoplt engaged. Shortly thereafter the heading comparator warning illuminated, followed by an unsolicited autoplt disconnect. I took control of the aircraft, continuing the descent and attempting to maintain wings level. Compasses were noted to be 10-15 degrees in disagreement. The first officer began the laborious process of checking the wet compass. We determined my rmdi to be in error and reslaved it. Almost immediately we again received the heading warning. This time it appeared to be the first officer's rmdi that was in error. Both VOR needles (both tuned and idented to fgt) were also observed to be split approximately 30 degrees. At this point center asked if we were proceeded direct fgt. We replied that we were. Center informed us we appeared to be tracking direct flying cloud. At this point we reported compass problems. Center acknowledged and switched us to msp approach control. We again reported our difficulties to approach. Approach told us to hold what we had, adding he'd keep an eye on us. Once level we successfully slaved the rmdi's. Approach and landing were west/O incident. Though we made our crossing, I estimate we passed 10-15 mi to the west of fgt. The descent was made in moderate chop and precipitation, with evidence of st elmo's fire and a great deal of static electricity. I've never experienced both rmdi's and VOR's behaving erratically, though I've flown this type aircraft in similar meteorological conditions numerous times. We were operating at reduced airspeed and did not have a static discharge. More than anything, poor human engineering caused this incident. The wet compass is located in the bulkhead, behind and above the first officer's head. A mirror must be adjusted on the glareshield to reference it. Had it been mounted forward, in the pilot's line of sight, I feel we would have resolved the situation much more quickly.

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Original NASA ASRS Text

Title: ACR MLG HEADING DEVIATION DUE COMPASS PROBLEMS ON DESCENT INTO MSP.

Narrative: CLRED BY ZMP DIRECT FGT VOR, WITH PLT'S DISCRETION TO CROSS 15 DME S AT OR BELOW 15000' TO MAINTAIN 10000'. DSCNT WAS INITIATED AT 65 DME WITH THE AUTOPLT ENGAGED. SHORTLY THEREAFTER THE HDG COMPARATOR WARNING ILLUMINATED, FOLLOWED BY AN UNSOLICITED AUTOPLT DISCONNECT. I TOOK CONTROL OF THE ACFT, CONTINUING THE DSCNT AND ATTEMPTING TO MAINTAIN WINGS LEVEL. COMPASSES WERE NOTED TO BE 10-15 DEGS IN DISAGREEMENT. THE F/O BEGAN THE LABORIOUS PROCESS OF CHKING THE WET COMPASS. WE DETERMINED MY RMDI TO BE IN ERROR AND RESLAVED IT. ALMOST IMMEDIATELY WE AGAIN RECEIVED THE HDG WARNING. THIS TIME IT APPEARED TO BE THE F/O'S RMDI THAT WAS IN ERROR. BOTH VOR NEEDLES (BOTH TUNED AND IDENTED TO FGT) WERE ALSO OBSERVED TO BE SPLIT APPROX 30 DEGS. AT THIS POINT CENTER ASKED IF WE WERE PROCEEDED DIRECT FGT. WE REPLIED THAT WE WERE. CENTER INFORMED US WE APPEARED TO BE TRACKING DIRECT FLYING CLOUD. AT THIS POINT WE RPTED COMPASS PROBS. CENTER ACKNOWLEDGED AND SWITCHED US TO MSP APCH CTL. WE AGAIN RPTED OUR DIFFICULTIES TO APCH. APCH TOLD US TO HOLD WHAT WE HAD, ADDING HE'D KEEP AN EYE ON US. ONCE LEVEL WE SUCCESSFULLY SLAVED THE RMDI'S. APCH AND LNDG WERE W/O INCIDENT. THOUGH WE MADE OUR XING, I ESTIMATE WE PASSED 10-15 MI TO THE W OF FGT. THE DSCNT WAS MADE IN MODERATE CHOP AND PRECIPITATION, WITH EVIDENCE OF ST ELMO'S FIRE AND A GREAT DEAL OF STATIC ELECTRICITY. I'VE NEVER EXPERIENCED BOTH RMDI'S AND VOR'S BEHAVING ERRATICALLY, THOUGH I'VE FLOWN THIS TYPE ACFT IN SIMILAR METEOROLOGICAL CONDITIONS NUMEROUS TIMES. WE WERE OPERATING AT REDUCED AIRSPD AND DID NOT HAVE A STATIC DISCHARGE. MORE THAN ANYTHING, POOR HUMAN ENGINEERING CAUSED THIS INCIDENT. THE WET COMPASS IS LOCATED IN THE BULKHEAD, BEHIND AND ABOVE THE F/O'S HEAD. A MIRROR MUST BE ADJUSTED ON THE GLARESHIELD TO REF IT. HAD IT BEEN MOUNTED FORWARD, IN THE PLT'S LINE OF SIGHT, I FEEL WE WOULD HAVE RESOLVED THE SITUATION MUCH MORE 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.