Narrative:

During arrival into newark while level at 6000 ft and on with new york approach; we received a TCAS alert 'traffic!' a target appeared approx. 5 nm ahead at the same altitude. We next got a 'descend descend' alert and the vsi indicated approximately a 2000 ft/min descent rate to avoid the conflict (green area). I disconnected the autopilot and immediately initiated an appropriate descent to avoid the conflict. We further received an alert 'increase rate of descent' and the target was now same altitude within the 4 nm ring on the TCAS. Seconds later we received a 'clear of conflict' and the target disappeared. At this point we had descended to approximately 5600 ft and initiated a climb to return to our assigned altitude. We advised ATC of our TCAS RA descent. They inquired what traffic we were descending for but at this point the only aircraft near our altitude was 7-8 miles away and clearly not a conflict. Approach seemed to think we were descending for a previously called traffic which we had reported in sight; but we repeatedly told him that we had had the previous traffic and it had long passed behind us and was not a factor. We never saw the actual conflict traffic; it only appeared on the TCAS. I'm not sure if this was a glitch in our TCAS or someone had a faulty mode C. The flight landed without further incident.

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Original NASA ASRS Text

Title: The crew received a TA (traffic alert) followed by an RA (resolution advisory) and took appropriate evasive action. It appears to have been a false target.

Narrative: During arrival into Newark while level at 6000 ft and on with New York Approach; we received a TCAS alert 'Traffic!' A target appeared approx. 5 nm ahead at the same altitude. We next got a 'Descend Descend' alert and the VSI indicated approximately a 2000 ft/min descent rate to avoid the conflict (green area). I disconnected the autopilot and immediately initiated an appropriate descent to avoid the conflict. We further received an alert 'Increase rate of descent' and the target was now same altitude within the 4 nm ring on the TCAS. Seconds later we received a 'Clear of conflict' and the target disappeared. At this point we had descended to approximately 5600 ft and initiated a climb to return to our assigned altitude. We advised ATC of our TCAS RA descent. They inquired what traffic we were descending for but at this point the only aircraft near our altitude was 7-8 miles away and clearly not a conflict. Approach seemed to think we were descending for a previously called traffic which we had reported in sight; but we repeatedly told him that we had had the previous traffic and it had long passed behind us and was not a factor. We never saw the actual conflict traffic; it only appeared on the TCAS. I'm not sure if this was a glitch in our TCAS or someone had a faulty Mode C. The flight landed without further incident.

Data retrieved from NASA's ASRS site 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.