Narrative:

While being vectored for visual, cessna VFR traffic was called out at 4000 ft MSL. We advised ATC that traffic was not in sight. He held us up at 4500 ft MSL and turned us in to pass behind traffic. We then received a TCASII alert and RA to descend immediately. After complying with that, we received an additional RA to monitor vertical speed to avoid commuter traffic. We complied with that. Only at last min did we see VFR cessna traffic, but had commuter traffic in sight at all times. Supplemental information from ACN471156: air carrier descending north of pdx on downwind. I called VFR traffic and stopped it at 4500 ft. At the time, the VFR traffic was at 4000 ft. The VFR traffic continued to climb northeast. The air carrier verified that the traffic was a correct altitude readout. This aircraft had a transponder with mode C readouts, but was not talking to pdx approach. The VFR aircraft was in the class C airspace. If pdx had a class B airspace this near miss could have been possibly avoided, because the VFR aircraft would be required to call us.

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Original NASA ASRS Text

Title: TCASII RA AND AIRSPACE ENTRY WITHOUT CLRNC IN PDX CLASS C AIRSPACE.

Narrative: WHILE BEING VECTORED FOR VISUAL, CESSNA VFR TFC WAS CALLED OUT AT 4000 FT MSL. WE ADVISED ATC THAT TFC WAS NOT IN SIGHT. HE HELD US UP AT 4500 FT MSL AND TURNED US IN TO PASS BEHIND TFC. WE THEN RECEIVED A TCASII ALERT AND RA TO DSND IMMEDIATELY. AFTER COMPLYING WITH THAT, WE RECEIVED AN ADDITIONAL RA TO MONITOR VERT SPD TO AVOID COMMUTER TFC. WE COMPLIED WITH THAT. ONLY AT LAST MIN DID WE SEE VFR CESSNA TFC, BUT HAD COMMUTER TFC IN SIGHT AT ALL TIMES. SUPPLEMENTAL INFO FROM ACN471156: ACR DSNDING N OF PDX ON DOWNWIND. I CALLED VFR TFC AND STOPPED IT AT 4500 FT. AT THE TIME, THE VFR TFC WAS AT 4000 FT. THE VFR TFC CONTINUED TO CLB NE. THE ACR VERIFIED THAT THE TFC WAS A CORRECT ALT READOUT. THIS ACFT HAD A XPONDER WITH MODE C READOUTS, BUT WAS NOT TALKING TO PDX APCH. THE VFR ACFT WAS IN THE CLASS C AIRSPACE. IF PDX HAD A CLASS B AIRSPACE THIS NEAR MISS COULD HAVE BEEN POSSIBLY AVOIDED, BECAUSE THE VFR ACFT WOULD BE REQUIRED TO CALL US.

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.