Narrative:

VMC day on approach control frequency and level at 9000' MSL. Being vectored to a downwind for 36L at clt. TCAS on and in use. Both pilots qualified in TCAS. TA issued with verbal, 'traffic, traffic,' followed shortly by an RA and a verbal, 'climb, climb;' vvf command of 2500 FPM climb. Copilot (PF) disconnected the autoplt. I told him to climb, as I searched visually for the traffic (Y). Traffic was spotted in a climbing turn toward us and below us (1000' lower, 1/4 mi and at our 11 O'clock position). I simultaneously called clt approach and told them we had climbed to 9600' in response to a TCAS RA. Clear of conflict, we descended back to 9000'. TCAS announced, 'clear of traffic.' approach called out the traffic to us only after we had climbed and had called them. Back on the ground, I talked to the approach supervisor concerning the incident. He said he was required to submit his own report on the TCAS induced deviation. He indicated the conflicting traffic (Y) was at 7400' and climbing to an assigned altitude of 8000' when we departed 9000'. From the training we received, likewise we must follow the RA assuming no conflicting information not to. Even if the conflicting traffic is spotted visually, are we sure that's the traffic TCAS is alerting us to? It seems to me that a false RA can be generated by a quickly climbing/descending aircraft, even if the aircraft intends to level off 1000' below/above my aircraft. Is this going to be a common occurrence? Are we still getting the bugs out of the system at a time when it is being operationally put out into the field?

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Original NASA ASRS Text

Title: APPARENTLY FALSE TCAS ALERT LEADS TO ALT EXCURSION FOR ACR MLG FLT CREW.

Narrative: VMC DAY ON APCH CTL FREQ AND LEVEL AT 9000' MSL. BEING VECTORED TO A DOWNWIND FOR 36L AT CLT. TCAS ON AND IN USE. BOTH PLTS QUALIFIED IN TCAS. TA ISSUED WITH VERBAL, 'TFC, TFC,' FOLLOWED SHORTLY BY AN RA AND A VERBAL, 'CLB, CLB;' VVF COMMAND OF 2500 FPM CLB. COPLT (PF) DISCONNECTED THE AUTOPLT. I TOLD HIM TO CLB, AS I SEARCHED VISUALLY FOR THE TFC (Y). TFC WAS SPOTTED IN A CLBING TURN TOWARD US AND BELOW US (1000' LOWER, 1/4 MI AND AT OUR 11 O'CLOCK POS). I SIMULTANEOUSLY CALLED CLT APCH AND TOLD THEM WE HAD CLBED TO 9600' IN RESPONSE TO A TCAS RA. CLR OF CONFLICT, WE DSNDED BACK TO 9000'. TCAS ANNOUNCED, 'CLR OF TFC.' APCH CALLED OUT THE TFC TO US ONLY AFTER WE HAD CLBED AND HAD CALLED THEM. BACK ON THE GND, I TALKED TO THE APCH SUPVR CONCERNING THE INCIDENT. HE SAID HE WAS REQUIRED TO SUBMIT HIS OWN RPT ON THE TCAS INDUCED DEVIATION. HE INDICATED THE CONFLICTING TFC (Y) WAS AT 7400' AND CLBING TO AN ASSIGNED ALT OF 8000' WHEN WE DEPARTED 9000'. FROM THE TRNING WE RECEIVED, LIKEWISE WE MUST FOLLOW THE RA ASSUMING NO CONFLICTING INFO NOT TO. EVEN IF THE CONFLICTING TFC IS SPOTTED VISUALLY, ARE WE SURE THAT'S THE TFC TCAS IS ALERTING US TO? IT SEEMS TO ME THAT A FALSE RA CAN BE GENERATED BY A QUICKLY CLBING/DSNDING ACFT, EVEN IF THE ACFT INTENDS TO LEVEL OFF 1000' BELOW/ABOVE MY ACFT. IS THIS GOING TO BE A COMMON OCCURRENCE? ARE WE STILL GETTING THE BUGS OUT OF THE SYS AT A TIME WHEN IT IS BEING OPERATIONALLY PUT OUT INTO THE FIELD?

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.