Narrative:

In cruise at FL330, cleared direct ilm VOR (wilmington, nc), #2 compass system continually malfunctioned, captain's RMI precessing approximately 15 degree every 5 mins. Solved compass problem by switching both compasses to #1 compass system. When switching compasses, omega navigation and autoplt both disconnected. Aircraft immediately entered left climbing turn. Took manual control of aircraft returned aircraft to proper heading and altitude. However, aircraft turned about 25 degree off heading and climbed to 33300' MSL before returning to normal. Jax center called and advised 'southbound traffic Y, 12 O'clock, 2 mi, FL350.' we advised that we were just returning to level flight at FL330. Autoplt, omega navigation, and compass system (both on compass #1) worked normally remainder of flight. Upon arrival at destination, entered compass problem in aircraft maintenance logbook. Maintenance replaced #1 vertical gyro and all system worked normal next leg. The entire altitude deviation lasted no longer than approximately 30 seconds, but unfortunately it occurred close to another aircraft (we never did see the other aircraft) and the required vertical sep may have been compromised. The only way to have avoided this incident, given the circumstances (autoplt and omega navigation immediately disconnecting and aircraft entering climb and turn) would have been to immediately overctl the aircraft with an abrupt pitch down. However, this would have been uncomfortable and possibly even dangerous for the passengers and F/as moving about (seat belt sign was off). We were not advised of the traffic at FL350 prior to the incident.

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Original NASA ASRS Text

Title: GYRO MALFUNCTION LEADS TO HEADING AND ALT EXCURSION FOR ACR LGT. LOSS OF SEPARATION OCCURS.

Narrative: IN CRUISE AT FL330, CLRED DIRECT ILM VOR (WILMINGTON, NC), #2 COMPASS SYS CONTINUALLY MALFUNCTIONED, CAPT'S RMI PRECESSING APPROX 15 DEG EVERY 5 MINS. SOLVED COMPASS PROB BY SWITCHING BOTH COMPASSES TO #1 COMPASS SYS. WHEN SWITCHING COMPASSES, OMEGA NAV AND AUTOPLT BOTH DISCONNECTED. ACFT IMMEDIATELY ENTERED L CLBING TURN. TOOK MANUAL CTL OF ACFT RETURNED ACFT TO PROPER HDG AND ALT. HOWEVER, ACFT TURNED ABOUT 25 DEG OFF HDG AND CLBED TO 33300' MSL BEFORE RETURNING TO NORMAL. JAX CTR CALLED AND ADVISED 'SBND TFC Y, 12 O'CLOCK, 2 MI, FL350.' WE ADVISED THAT WE WERE JUST RETURNING TO LEVEL FLT AT FL330. AUTOPLT, OMEGA NAV, AND COMPASS SYS (BOTH ON COMPASS #1) WORKED NORMALLY REMAINDER OF FLT. UPON ARR AT DEST, ENTERED COMPASS PROB IN ACFT MAINT LOGBOOK. MAINT REPLACED #1 VERT GYRO AND ALL SYS WORKED NORMAL NEXT LEG. THE ENTIRE ALT DEV LASTED NO LONGER THAN APPROX 30 SECS, BUT UNFORTUNATELY IT OCCURRED CLOSE TO ANOTHER ACFT (WE NEVER DID SEE THE OTHER ACFT) AND THE REQUIRED VERT SEP MAY HAVE BEEN COMPROMISED. THE ONLY WAY TO HAVE AVOIDED THIS INCIDENT, GIVEN THE CIRCUMSTANCES (AUTOPLT AND OMEGA NAV IMMEDIATELY DISCONNECTING AND ACFT ENTERING CLB AND TURN) WOULD HAVE BEEN TO IMMEDIATELY OVERCTL THE ACFT WITH AN ABRUPT PITCH DOWN. HOWEVER, THIS WOULD HAVE BEEN UNCOMFORTABLE AND POSSIBLY EVEN DANGEROUS FOR THE PAXS AND F/AS MOVING ABOUT (SEAT BELT SIGN WAS OFF). WE WERE NOT ADVISED OF THE TFC AT FL350 PRIOR TO THE INCIDENT.

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.