Narrative:

While being turned southwest, off of the arrival on vectors headed west at 10000 ft, we were given notice of VFR traffic climbing sbound. I believe the controller said 'you do have that traffic climbing VFR at 1 O'clock position, don't you?' almost immediately we had a TCASII alert calling 'traffic, traffic.' I looked at the TCASII screen to see the traffic indeed climbing toward us. It immediately turned from yellow to red at which time the TCASII RA called for us to descend. The captain began a descent and I called to ATC 'air carrier X descending, RA.' I looked at TCASII to see to my surprise that the traffic was climbing through 9500 ft. The captain began to turn while descending. TCASII called 'increase descent rate' and ATC called for us to turn right. I misunderstood the heading as the TCASII aural warning drowned out the ATC voice command. ATC corrected my heading readback, but the captain had already heard the correct heading, told me so, and was turning to it. While in a descending right bank, I looked up and through the captain's windscreen and 'dv' window saw a king air 90 with the door removed pass by right to left. My estimate was 1/4 - 1/2 mi and a few hundred ft separation. After conflict resolution, the captain began a climb to the previously assigned altitude. Very shortly thereafter, ATC gave us vectors and a descent toward sjc. ATC did not inform us of the VFR traffic until it was almost too late. ATC advised us only once of the traffic -- when he questioned us if we had them in sight. It is the opinion of the captain and I that without TCASII it would have been a midair collision.

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Original NASA ASRS Text

Title: MD SUPER 80 FLC TOOK EVASIVE ACTION BY DSNDING AND TURNING IN RESPONSE TO A TCASII RA OF A KING AIR ACFT.

Narrative: WHILE BEING TURNED SW, OFF OF THE ARR ON VECTORS HEADED W AT 10000 FT, WE WERE GIVEN NOTICE OF VFR TFC CLBING SBOUND. I BELIEVE THE CTLR SAID 'YOU DO HAVE THAT TFC CLBING VFR AT 1 O'CLOCK POS, DON'T YOU?' ALMOST IMMEDIATELY WE HAD A TCASII ALERT CALLING 'TFC, TFC.' I LOOKED AT THE TCASII SCREEN TO SEE THE TFC INDEED CLBING TOWARD US. IT IMMEDIATELY TURNED FROM YELLOW TO RED AT WHICH TIME THE TCASII RA CALLED FOR US TO DSND. THE CAPT BEGAN A DSCNT AND I CALLED TO ATC 'ACR X DSNDING, RA.' I LOOKED AT TCASII TO SEE TO MY SURPRISE THAT THE TFC WAS CLBING THROUGH 9500 FT. THE CAPT BEGAN TO TURN WHILE DSNDING. TCASII CALLED 'INCREASE DSCNT RATE' AND ATC CALLED FOR US TO TURN R. I MISUNDERSTOOD THE HDG AS THE TCASII AURAL WARNING DROWNED OUT THE ATC VOICE COMMAND. ATC CORRECTED MY HDG READBACK, BUT THE CAPT HAD ALREADY HEARD THE CORRECT HDG, TOLD ME SO, AND WAS TURNING TO IT. WHILE IN A DSNDING R BANK, I LOOKED UP AND THROUGH THE CAPT'S WINDSCREEN AND 'DV' WINDOW SAW A KING AIR 90 WITH THE DOOR REMOVED PASS BY R TO L. MY ESTIMATE WAS 1/4 - 1/2 MI AND A FEW HUNDRED FT SEPARATION. AFTER CONFLICT RESOLUTION, THE CAPT BEGAN A CLB TO THE PREVIOUSLY ASSIGNED ALT. VERY SHORTLY THEREAFTER, ATC GAVE US VECTORS AND A DSCNT TOWARD SJC. ATC DID NOT INFORM US OF THE VFR TFC UNTIL IT WAS ALMOST TOO LATE. ATC ADVISED US ONLY ONCE OF THE TFC -- WHEN HE QUESTIONED US IF WE HAD THEM IN SIGHT. IT IS THE OPINION OF THE CAPT AND I THAT WITHOUT TCASII IT WOULD HAVE BEEN A MIDAIR COLLISION.

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.