Narrative:

Plane had just come out of annual. Most switches on panel were off or in different position (this should not be since there was a master avionics switch). The slave button for the slaved gyroscope compass was out. There seemed to be a discrepancy between the magnetic and slaved gyroscope, approximately 30-50 degrees. I considered that this might be a necessary heading correction (for winds aloft) to stay on a GPS victor airway course (autoplt) while in the navigation position. After watching through several victor airways (V489 and V449) with changes in heading from 180 degrees to 250 degrees (and since it was good VFR) I decided to disengage the slave button and to immediately re-engage it to see if this would align the compasses. I did not disengage the autoplt during this so that proper altitude would be maintained. The plane immediately started turning to the left as the gyroscope compass went out of control. I tried to resolve this by focusing on the magnetic compass but it was swinging too wildly to use it. The plane turned close to 180 degrees before the compasses stabilized and then I put the autoplt on the heading bug to try to get back on course. At this time ZBW asked me what was going on since I seemed to be heading in an opposite direction. I explained the autoplt slaved gyroscope compass problem and they offered me direct to dny and said they would monitor my track to help me if necessary. Shortly thereafter we both agreed that the tracking was good although there was still a discrepancy in the compass. A solution would have been to place the autoplt in the heading mode before disengaging the slaved gyroscope but I didn't realize the slaved gyroscope would spin to the left. The plane was returned to FBO yesterday and they said perhaps the wrong screws were used in the vicinity of the magnetic compass and were going to test the gyroscope compass on a compass rose and hopefully the compasses will show the same headings. I also would not have done this unless it was good VFR but perhaps I should have taken the plane up on a separate flight to test this.

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Original NASA ASRS Text

Title: PLT OF A BEECH BARON, BE55, ON AN IFR FLT AFTER AN ANNUAL INSPECTION OF THE ACFT, FOUND THAT THE DIRECTIONAL GYROSCOPE WOULD NOT STAY IN THE SLAVED MODE RESULTING IN ATC INTERVENTION TO VECTOR THE RPTR TO TURN AROUND AND INTERCEPT FLT PLAN ROUTING.

Narrative: PLANE HAD JUST COME OUT OF ANNUAL. MOST SWITCHES ON PANEL WERE OFF OR IN DIFFERENT POS (THIS SHOULD NOT BE SINCE THERE WAS A MASTER AVIONICS SWITCH). THE SLAVE BUTTON FOR THE SLAVED GYROSCOPE COMPASS WAS OUT. THERE SEEMED TO BE A DISCREPANCY BTWN THE MAGNETIC AND SLAVED GYROSCOPE, APPROX 30-50 DEGS. I CONSIDERED THAT THIS MIGHT BE A NECESSARY HEADING CORRECTION (FOR WINDS ALOFT) TO STAY ON A GPS VICTOR AIRWAY COURSE (AUTOPLT) WHILE IN THE NAV POS. AFTER WATCHING THROUGH SEVERAL VICTOR AIRWAYS (V489 AND V449) WITH CHANGES IN HEADING FROM 180 DEGS TO 250 DEGS (AND SINCE IT WAS GOOD VFR) I DECIDED TO DISENGAGE THE SLAVE BUTTON AND TO IMMEDIATELY RE-ENGAGE IT TO SEE IF THIS WOULD ALIGN THE COMPASSES. I DID NOT DISENGAGE THE AUTOPLT DURING THIS SO THAT PROPER ALT WOULD BE MAINTAINED. THE PLANE IMMEDIATELY STARTED TURNING TO THE L AS THE GYROSCOPE COMPASS WENT OUT OF CTL. I TRIED TO RESOLVE THIS BY FOCUSING ON THE MAGNETIC COMPASS BUT IT WAS SWINGING TOO WILDLY TO USE IT. THE PLANE TURNED CLOSE TO 180 DEGS BEFORE THE COMPASSES STABILIZED AND THEN I PUT THE AUTOPLT ON THE HEADING BUG TO TRY TO GET BACK ON COURSE. AT THIS TIME ZBW ASKED ME WHAT WAS GOING ON SINCE I SEEMED TO BE HEADING IN AN OPPOSITE DIRECTION. I EXPLAINED THE AUTOPLT SLAVED GYROSCOPE COMPASS PROB AND THEY OFFERED ME DIRECT TO DNY AND SAID THEY WOULD MONITOR MY TRACK TO HELP ME IF NECESSARY. SHORTLY THEREAFTER WE BOTH AGREED THAT THE TRACKING WAS GOOD ALTHOUGH THERE WAS STILL A DISCREPANCY IN THE COMPASS. A SOLUTION WOULD HAVE BEEN TO PLACE THE AUTOPLT IN THE HEADING MODE BEFORE DISENGAGING THE SLAVED GYROSCOPE BUT I DIDN'T REALIZE THE SLAVED GYROSCOPE WOULD SPIN TO THE L. THE PLANE WAS RETURNED TO FBO YESTERDAY AND THEY SAID PERHAPS THE WRONG SCREWS WERE USED IN THE VICINITY OF THE MAGNETIC COMPASS AND WERE GOING TO TEST THE GYROSCOPE COMPASS ON A COMPASS ROSE AND HOPEFULLY THE COMPASSES WILL SHOW THE SAME HEADINGS. I ALSO WOULD NOT HAVE DONE THIS UNLESS IT WAS GOOD VFR BUT PERHAPS I SHOULD HAVE TAKEN THE PLANE UP ON A SEPARATE FLT TO TEST THIS.

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.