HS125-700 FLT CREW ENRTE TO MDW RECEIVED BAD INFO FROM FMS; LEADING TO A COURSE DEV.

Narrative

WHILE CRUISING ON J60 ENRTE TO MDW ARPT; IN BTWN NAPOL INTXN AND ASHEN INTXN; OUR #1 GNS BOX STARTED TO GIVE US BAD INFO. THE 2 GNS BOXES HAD BEEN XFILLED FOR ALL FLT PLAN DATA AT THE BEGINNING OF THE FLT. THIS MEANING ONE GNS GETS ITS FLT PLAN FROM THE OTHER. UPON REACHING ROUGHLY NAPOL INTXN; BOTH PLTS COMMENTED ON THE TURN THE ACFT MADE TO THE NEXT FIX. WE NOTICED THE PRIMARY GNS HAD AN UNUSUAL DISPLAY AND WENT BACK TO NORMAL -- WE THOUGHT. A FEW MINS LATER; I LOOKED DOWN AND SAW THAT THE #1 GNS SAID IT WAS NAVING TO NAPOL; WHICH WAS BEHIND US; AND THE #2 GNS SAID WE ARE ENRTE TO ASHEN INTXN. THE ACFT APPEARED TO BE HOLDING A RANDOM HDG ABOUT 40 DEGS OFF COURSE. AT THIS TIME; CTR CALLED AND ASKED WHERE WE WERE GOING; AND TO GO TO GOSHEN. THAT WAS THE END OF THE EVENT; BUT WE BOTH STILL WONDER WHAT HAPPENED. THIS IS A PRIME EXAMPLE OF TODAY'S WORLD OF TECHNOLOGY; WHY WE SHOULD ALL STILL FOLLOW ALONG OUR RTE WITH AN OLD FASHIONED CHART. I WISH WE WOULD HAVE HAD OURS OUT OF THE BINDER.