CE550 FLT CREW HAS A TRACK HDG DEV AT FL320.

Narrative

ACFT HAD A VERY UNUSUAL EFIS SYS THAT I NEVER KNEW EXISTED. BUT CRUISING AT FL320 AND EVERYTHING WAS FINE. HAD QUESTIONS ABOUT THE EFIS; STC'S AND 1 ITEM ON A CHKLIST THAT DISAGREED WITH ANOTHER CHKLIST IN THE PLANE SO I GRABBED THE AFM TO LOOK IT UP. COPLT WAS LOOKING OUTSIDE SO I BURIED MY ATTN IN THE BOOK. AFTER ABOUT 5-10 MINS I LOOKED UP AND IT LOOKED LIKE THE ATTITUDE INDICATOR WAS SHOWING A LITTLE 3-4 DEG BANK TO THE L. FIGURED I WAS JUST TIRED AND SEEING THINGS; LOOKED ELSEWHERE AND EVERYTHING WAS FINE SO IT WAS BACK INTO THE BOOK. AFTER AN UNDETERMINED TIME; PROBABLY AROUND 1 MIN; ATC CALLED AND ASKED US IF WE WERE DIRECT TO MCC (OUR DEST). I LOOKED UP AND FIGURED OUT WHAT WAS GOING WRONG; CONFESSED TO ATC AND BEGAN CORRECTING USING THE HDG MODE. WE WERE ALMOST 45 DEGS OFF OUR COURSE (ABOUT 240 DEGS) AND HEADED FOR THE MIL AIRSPACE E OF RENO. THE CTLR THEN MENTIONED THIS AND GAVE US A HDG OF 270 DEGS TO KEEP US OUT. THE COPLT SET THE HDG BUG AND WE WERE ON OUR WAY. THE CTLR ASKED US FOR OUR BEST TURN RATE; SO I USED THE TURN KNOB ON THE AUTOPLT CTL HEAD; BUT THIS DID NOT GIVE MORE THAN ABOUT A 17 DEG BANK ANGLE; SO I DISCONNECTED THE AUTOPLT AND SET UP A 30 DEG TURN. SHORTLY THEREAFTER WE WERE CLRED DIRECT TO DEST. THE NAV MODE WAS COUPLED TO THE GNS/XLS AND HAD DISENGAGED WITHOUT OUR KNOWLEDGE. WHEN I GRABBED THE AUTOPLT TURN KNOB IT WAS CTRED AS I RECALL. SO HOW DID WE LOSE OUR NAV COUPLING? HOW DID THE PLANE GET INTO THAT BANK IF THE TURN KNOB WASN'T MOVED? NORMALLY WHEN THE NAV COUPLING IS LOST; THE PLANE WILL JUST FLY WINGS LEVEL. I DID NOTICE THAT THE EFIS; FMS AND AUTOPLT WERE FROM 3 DIFFERENT VENDORS AND DID NOT ALWAYS DO A GOOD JOB OF ACQUIRING A GPS TRACK TOGETHER AND REQUIRED SOME EXTRA ATTN WHEN COMMANDING A 'DIRECT TO.' ONCE ACQUIRED THINGS SEEMED TO GO WELL THOUGH.