Narrative:

Approach control advised us that there would be traffic climbing to 500 ft below our altitude. We picked up traffic on TCASII display verifying approach control advisory. At that time the aircraft was about 10 mi in front of us, no visual yet. We are cruising at 320 KTS. TCASII issued traffic warning. Still no visual. At 5 mi with TCASII showing a climb on target, the captain called approach control, advised them we are turning to avoid the target. Approach control said that there is no need for that, due to the fact that the target aircraft was assigned 500 ft below our altitude. At this point, I saw the target aircraft pass off our right side 3 O'clock position by 500 ft maximum and below us. If the aircraft hadn't turned, I'm sure the target would have turned into an RA and issued a climb command. The captain tried to explain that at 320 KTS we wouldn't have had any time to react if the target was off his assigned altitude. There was no other traffic on the TCASII. Approach control should have given us a short turn to avoid the climbing traffic. We never went more than a mi on our deviation.

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Original NASA ASRS Text

Title: AN ACR MLG TURNED TO AVOID A POSSIBLE TCASII ALERT ACTIVATION.

Narrative: APCH CTL ADVISED US THAT THERE WOULD BE TFC CLBING TO 500 FT BELOW OUR ALT. WE PICKED UP TFC ON TCASII DISPLAY VERIFYING APCH CTL ADVISORY. AT THAT TIME THE ACFT WAS ABOUT 10 MI IN FRONT OF US, NO VISUAL YET. WE ARE CRUISING AT 320 KTS. TCASII ISSUED TFC WARNING. STILL NO VISUAL. AT 5 MI WITH TCASII SHOWING A CLB ON TARGET, THE CAPT CALLED APCH CTL, ADVISED THEM WE ARE TURNING TO AVOID THE TARGET. APCH CTL SAID THAT THERE IS NO NEED FOR THAT, DUE TO THE FACT THAT THE TARGET ACFT WAS ASSIGNED 500 FT BELOW OUR ALT. AT THIS POINT, I SAW THE TARGET ACFT PASS OFF OUR R SIDE 3 O'CLOCK POS BY 500 FT MAX AND BELOW US. IF THE ACFT HADN'T TURNED, I'M SURE THE TARGET WOULD HAVE TURNED INTO AN RA AND ISSUED A CLB COMMAND. THE CAPT TRIED TO EXPLAIN THAT AT 320 KTS WE WOULDN'T HAVE HAD ANY TIME TO REACT IF THE TARGET WAS OFF HIS ASSIGNED ALT. THERE WAS NO OTHER TFC ON THE TCASII. APCH CTL SHOULD HAVE GIVEN US A SHORT TURN TO AVOID THE CLBING TFC. WE NEVER WENT MORE THAN A MI ON OUR DEV.

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.