Narrative:

Our aircraft, an medium large transport, was IMC inbound to dxo VOR on the STAR arrival into dtw known as the polar 1 arrival. Dtw approach had slowed us to 210 KIAS and instructed us to turn to 190 degrees heading at traml intersection. We were 2 DME from traml (12 DME from dxo) when TCASII announced 'traffic, traffic.' I noted a yellow globe at our 10 O'clock below us climbing on TCASII display. TCASII then commanded 'climb, climb, now.' the ivsi showed a red arc from -6000 FPM to +1500 FPM and green arc from +1500 to +2000 FPM. The first officer was flying on autoplt altitude hold. I instructed the first officer to climb and, in fact, assisted him by disconnecting the autoplt. He climbed the aircraft into the green arc, climbing at 1600 FPM. At approximately 11300 ft the TCASII red and green arcs disappeared and TCASII announced 'clear of conflict.' the 'round out' gave us an altitude of 11500 MSL before descending back down to 11000 MSL assigned. At the onset of our TCASII commanded climb I notified dtw approach we were in a TCASII commanded climb. The dtw approach controller said there was in fact traffic climbing out of dtw below us. I cannot and do not recall seeing the yellow TCASII symbol depiction any closer than 900 ft.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION DURING TCASII RA.

Narrative: OUR ACFT, AN MLG, WAS IMC INBOUND TO DXO VOR ON THE STAR ARR INTO DTW KNOWN AS THE POLAR 1 ARR. DTW APCH HAD SLOWED US TO 210 KIAS AND INSTRUCTED US TO TURN TO 190 DEGS HDG AT TRAML INTXN. WE WERE 2 DME FROM TRAML (12 DME FROM DXO) WHEN TCASII ANNOUNCED 'TFC, TFC.' I NOTED A YELLOW GLOBE AT OUR 10 O'CLOCK BELOW US CLBING ON TCASII DISPLAY. TCASII THEN COMMANDED 'CLB, CLB, NOW.' THE IVSI SHOWED A RED ARC FROM -6000 FPM TO +1500 FPM AND GREEN ARC FROM +1500 TO +2000 FPM. THE FO WAS FLYING ON AUTOPLT ALT HOLD. I INSTRUCTED THE FO TO CLB AND, IN FACT, ASSISTED HIM BY DISCONNECTING THE AUTOPLT. HE CLBED THE ACFT INTO THE GREEN ARC, CLBING AT 1600 FPM. AT APPROX 11300 FT THE TCASII RED AND GREEN ARCS DISAPPEARED AND TCASII ANNOUNCED 'CLR OF CONFLICT.' THE 'ROUND OUT' GAVE US AN ALT OF 11500 MSL BEFORE DSNDING BACK DOWN TO 11000 MSL ASSIGNED. AT THE ONSET OF OUR TCASII COMMANDED CLB I NOTIFIED DTW APCH WE WERE IN A TCASII COMMANDED CLB. THE DTW APCH CTLR SAID THERE WAS IN FACT TFC CLBING OUT OF DTW BELOW US. I CANNOT AND DO NOT RECALL SEEING THE YELLOW TCASII SYMBOL DEPICTION ANY CLOSER THAN 900 FT.

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.