Narrative:

A VFR aircraft popped up in front of widebody transport. The VFR's mode C indicated it was climbing. In my opinion prior to the VFR aircraft calling me, his mode C was off. I had just told widebody transport to contact the final controller when the VFR aircraft (small aircraft) turned on his mode C and made radio contact with me. Small aircraft also gave me a position report on his initial call. I quickly informed the final controller that widebody transport had traffic. Traffic was exchanged and widebody transport landed west/O further incident. Supplemental information from acn 150232. Widebody transport was in the process of a frequency change by the time I first spoke with widebody transport it was already too late to vector him away from the unident/uncertified VFR aircraft. Both controllers involved were very busy, there were no handoff controllers.

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Original NASA ASRS Text

Title: AN IFR ACFT ON AN APCH TO ARPT OF DESIGNATION CAME VERY CLOSE TO A VFR ACFT.

Narrative: A VFR ACFT POPPED UP IN FRONT OF WDB. THE VFR'S MODE C INDICATED IT WAS CLBING. IN MY OPINION PRIOR TO THE VFR ACFT CALLING ME, HIS MODE C WAS OFF. I HAD JUST TOLD WDB TO CONTACT THE FINAL CTLR WHEN THE VFR ACFT (SMA) TURNED ON HIS MODE C AND MADE RADIO CONTACT WITH ME. SMA ALSO GAVE ME A POS RPT ON HIS INITIAL CALL. I QUICKLY INFORMED THE FINAL CTLR THAT WDB HAD TFC. TFC WAS EXCHANGED AND WDB LANDED W/O FURTHER INCIDENT. SUPPLEMENTAL INFO FROM ACN 150232. WDB WAS IN THE PROCESS OF A FREQ CHANGE BY THE TIME I FIRST SPOKE WITH WDB IT WAS ALREADY TOO LATE TO VECTOR HIM AWAY FROM THE UNIDENT/UNCERTIFIED VFR ACFT. BOTH CTLRS INVOLVED WERE VERY BUSY, THERE WERE NO HDOF CTLRS.

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.