HDG TRACK POS DEV.

Narrative

ON FEB/XX/95 AT ABOUT XA00 PM SAN JUAN TIME WE DEPARTED RWY 8 ENRTE TO MIAMI. WE INTERCEPTED THE JAAWS 9 DEP; AND SHORTLY AFTER PASSING THROUGH 10000 FT WE WERE CLRED DIRECT (RNAV) TO JUNUR; WHICH IS A POINT IN THE CLAMI 1 ARR INTO MIAMI. I THEN ENGAGED THE AUTOPLT AND TURNED THE AIRPLANE IN THE DIRECTION OF THE WAYPOINT (JUNUR) WE WERE CLRED TO. AT THIS POINT I AM NOT SURE IF I ENGAGED THE AUX NAV PORTION OF THE AUTOPLT. THE REASON I SAY THIS IS BECAUSE APPROX 1 HR LATER WE DISCOVERED THAT THE AUX NAV PORTION OF THE AUTOPLT WAS NOT ENGAGED AND WE HAD DRIFTED ABOUT 45 NM OFF COURSE. IT IS UNKNOWN WHETHER THE AUX NAV WAS NEVER ENGAGED OR IF THE KNOB WAS SOMEHOW KNOCKED OFF DURING THE FLT. I DO REMEMBER PASSING ALMOST DIRECTLY OVER GTK VOR WHICH IS ALONG THE NORMAL RTE THE AIRPLANE WOULD TAKE IF THE OMEGA WERE ENGAGED. 2 SCENARIOS ARE POSSIBLE. THE OMEGA WAS NEVER ENGAGED; AND DUE TO LIGHT HIGH ALT WINDS; THE AIRPLANE AFTER INITIALLY BEING POINTED IN THE CORRECT DIRECTION; ONLY BEGAN TO DRIFT DRAMATICALLY AFTER PASSING GTK VOR. OR; THE AUX NAV KNOB WAS ACCIDENTLY DISENGAGED AND WAS NOT NOTICED. THERE IS NO AURAL OR OTHER TYPE WARNING WHEN THE OMEGA BECOMES DISENGAGED. THERE IS A GREEEN 'AUX NAV' LIGHT THAT IS ILLUMINATED WHEN ENGAGED; BUT THE LIGHT IS NOT VERY OBVIOUS TO THE CREW. SOME TYPE OF OBVIOUS WARNING (HAD IT BEEN AVAILABLE) WOULD HAVE ALERTED THE CREW IN THE EVENT OF AN INADVERTENT DISCONNECT. ONE THING WE FOUND UNUSUAL DURING OUR FLT WAS THAT ATC NEVER SAID A WORD TO US DURING OUR SMALL DETOUR.