Narrative:

Was level at 12000 MSL inbound to dtw, between layers with good visibility. Aircraft was TCASII equipped and it was on and functioning. At approximately the above named fix, we received a TCASII TA. We switched to 10 NM scale and noticed aircraft lights at our 2 O'clock position. Due to night lighting conditions it was hard to determine his exact altitude and direction of flight. We then received a TCASII RA 'climb, climb now' command and I placed the vertical speed indicator in the green arc that was indicated. The other crew members noted that his altitude was now 11700 MSL. We reached 12500 when the vertical speed indicator green arc indicated a descent and I returned the aircraft to its assigned altitude. When I initiated the RA escape maneuver, my first officer (another captain who is a line check airman and was giving me my initial operating experience as a captain new to this aircraft) advised ATC of what we were doing. The controller then advised us of the intruding traffic -- the first and only advisory we received. When asked again about how long the traffic had been on his scope, he answered 'I don't know.' the TCASII alerts and commands were both timely and accurate. The escape maneuver directed was followed in a smooth manner such that the cockpit crew were the only people on the aircraft aware of the problem. Had we not had the system on board, our vertical separation would have been less than 300 ft and, quite possibly, someone else would now be writing a much different report for the front page of a newspaper. Sign me a TCASII believer.

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Original NASA ASRS Text

Title: FLC OF LGT RESPONDED TO TCASII RA. OBSERVED TARGET OF INTRUDER ACFT PASS 800 FT BELOW AFTER 500 FT CLB TO AVOID. LATE TA.

Narrative: WAS LEVEL AT 12000 MSL INBOUND TO DTW, BTWN LAYERS WITH GOOD VISIBILITY. ACFT WAS TCASII EQUIPPED AND IT WAS ON AND FUNCTIONING. AT APPROX THE ABOVE NAMED FIX, WE RECEIVED A TCASII TA. WE SWITCHED TO 10 NM SCALE AND NOTICED ACFT LIGHTS AT OUR 2 O'CLOCK POS. DUE TO NIGHT LIGHTING CONDITIONS IT WAS HARD TO DETERMINE HIS EXACT ALT AND DIRECTION OF FLT. WE THEN RECEIVED A TCASII RA 'CLB, CLB NOW' COMMAND AND I PLACED THE VERT SPD INDICATOR IN THE GREEN ARC THAT WAS INDICATED. THE OTHER CREW MEMBERS NOTED THAT HIS ALT WAS NOW 11700 MSL. WE REACHED 12500 WHEN THE VERT SPD INDICATOR GREEN ARC INDICATED A DSCNT AND I RETURNED THE ACFT TO ITS ASSIGNED ALT. WHEN I INITIATED THE RA ESCAPE MANEUVER, MY FO (ANOTHER CAPT WHO IS A LINE CHK AIRMAN AND WAS GIVING ME MY INITIAL OPERATING EXPERIENCE AS A CAPT NEW TO THIS ACFT) ADVISED ATC OF WHAT WE WERE DOING. THE CTLR THEN ADVISED US OF THE INTRUDING TFC -- THE FIRST AND ONLY ADVISORY WE RECEIVED. WHEN ASKED AGAIN ABOUT HOW LONG THE TFC HAD BEEN ON HIS SCOPE, HE ANSWERED 'I DON'T KNOW.' THE TCASII ALERTS AND COMMANDS WERE BOTH TIMELY AND ACCURATE. THE ESCAPE MANEUVER DIRECTED WAS FOLLOWED IN A SMOOTH MANNER SUCH THAT THE COCKPIT CREW WERE THE ONLY PEOPLE ON THE ACFT AWARE OF THE PROBLEM. HAD WE NOT HAD THE SYS ON BOARD, OUR VERT SEPARATION WOULD HAVE BEEN LESS THAN 300 FT AND, QUITE POSSIBLY, SOMEONE ELSE WOULD NOW BE WRITING A MUCH DIFFERENT RPT FOR THE FRONT PAGE OF A NEWSPAPER. SIGN ME A TCASII BELIEVER.

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.