Narrative:

The flight was given a clearance change while en route. We were in the vicinity of the cross city VOR when ZJX cleared us to proceed direct john intersection, J-91 atl, direct louisville, in. We were using omega navigation system as the primary navigation system and programed the change. When we crossed john intersection the omega navigation system began to 'drift' and we paralleled J-91 instead of intercepting. Neither the captain nor myself noticed the 'drift' until approximately 40-50 NM southeast of atl. The atl controller called and asked why we were not navigating J-91. We then explained we were having omega navigation system problems and atl reclred us direct atl. We asked if we should contact them upon arriving at ind and they stated not to worry about it, that it was no problem. We navigated the rest of the flight using VOR as the primary navigation system and the flight was uneventful. I feel that this could have been avoided had we been monitoring the omega navigation system accuracy by utilizing the VOR system as a backup. This procedure is outlined in our operations manual and there is no substitution for good cross monitoring. We had flown 3 legs prior to this one and the omega navigation system had been working within limitations. I feel that this led us to become complacent in our duties which would have led to early detection of a problem. All 3 crew members learned a valuable lesson in cockpit resource management and that procedures are developed to keep us on course, and not just to keep us busy. I have learned to keep a good xchk of all navigation system. Early detection is the key.

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Original NASA ASRS Text

Title: HDG TRACK DEV DURING AN AMENDED CLRNC RTE CHANGE. ARTCC RADAR CTLR INTERVENTION.

Narrative: THE FLT WAS GIVEN A CLRNC CHANGE WHILE ENRTE. WE WERE IN THE VICINITY OF THE CROSS CITY VOR WHEN ZJX CLRED US TO PROCEED DIRECT JOHN INTXN, J-91 ATL, DIRECT LOUISVILLE, IN. WE WERE USING OMEGA NAV SYS AS THE PRIMARY NAV SYS AND PROGRAMED THE CHANGE. WHEN WE CROSSED JOHN INTXN THE OMEGA NAV SYS BEGAN TO 'DRIFT' AND WE PARALLELED J-91 INSTEAD OF INTERCEPTING. NEITHER THE CAPT NOR MYSELF NOTICED THE 'DRIFT' UNTIL APPROX 40-50 NM SE OF ATL. THE ATL CTLR CALLED AND ASKED WHY WE WERE NOT NAVING J-91. WE THEN EXPLAINED WE WERE HAVING OMEGA NAV SYS PROBS AND ATL RECLRED US DIRECT ATL. WE ASKED IF WE SHOULD CONTACT THEM UPON ARRIVING AT IND AND THEY STATED NOT TO WORRY ABOUT IT, THAT IT WAS NO PROB. WE NAVIGATED THE REST OF THE FLT USING VOR AS THE PRIMARY NAV SYS AND THE FLT WAS UNEVENTFUL. I FEEL THAT THIS COULD HAVE BEEN AVOIDED HAD WE BEEN MONITORING THE OMEGA NAV SYS ACCURACY BY UTILIZING THE VOR SYS AS A BACKUP. THIS PROC IS OUTLINED IN OUR OPS MANUAL AND THERE IS NO SUBSTITUTION FOR GOOD CROSS MONITORING. WE HAD FLOWN 3 LEGS PRIOR TO THIS ONE AND THE OMEGA NAV SYS HAD BEEN WORKING WITHIN LIMITATIONS. I FEEL THAT THIS LED US TO BECOME COMPLACENT IN OUR DUTIES WHICH WOULD HAVE LED TO EARLY DETECTION OF A PROB. ALL 3 CREW MEMBERS LEARNED A VALUABLE LESSON IN COCKPIT RESOURCE MGMNT AND THAT PROCS ARE DEVELOPED TO KEEP US ON COURSE, AND NOT JUST TO KEEP US BUSY. I HAVE LEARNED TO KEEP A GOOD XCHK OF ALL NAV SYS. EARLY DETECTION IS THE KEY.

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.