Narrative:

We were being vectored for a visual approach on a saturday morning. Our arrival into the cvg class C airspace was from the southwest. We were given a turn to the north to fly what could be called a right downwind for runway 18R. Approximately crossing the river northbound, we were given a descent to 2500 ft. At first I thought we would be quickly turned toward the airport. However, as we continued northbound I mentioned to the captain my discomfort with being vectored through the cincinnati west (I67) traffic pattern at 1900 ft AGL. We were keeping a sharp lookout for VFR traffic. Shortly after being turned into the localizer our TCASII issued an advisory for traffic at our 10 O'clock and less than a mi. The captain disconnected the autoplt and pushed the nose over to descend. Our traffic passed almost directly above us at 150 ft separation. While all this was happening. Approach control called out the traffic telling us this traffic had 'just popped up.' I believe this to be true as the traffic also suddenly appeared on our TCASII. I responded to the controller we had the traffic in sight. I also mentioned the altitude readout on the target of 2600 ft was correct, and that the aircraft was either an aztec or a twin comanche. As the traffic flew overhead I could tell it was a 1967 or newer, blue and white twin comanche with the miller conversion. The problem with this incident is the twin comanche was legal. This person was flying outside the class C airspace. My suggestion to prevent a similar occurrence is for cvg TRACON to avoid descending traffic inbound to cvg too soon. I think safety would be better served if aircraft inbound were kept higher -- especially over other airports in close proximity to the class C airspace. The cincinnati/northern kentucky international airport has evolved into a very busy hub for acrs and commuters. I think the airport is pushing the limits of class C protection. Personally, I do not like the idea of class B airspace if it is at all possible to avoid the taking of additional airspace. Unfortunately, I think many pilots transitioning the cvg area are unaware of just how busy the cincinnati/northern kentucky international airport has become. Perhaps the time has come for consideration of class B airspace.

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Original NASA ASRS Text

Title: NMAC.

Narrative: WE WERE BEING VECTORED FOR A VISUAL APCH ON A SATURDAY MORNING. OUR ARR INTO THE CVG CLASS C AIRSPACE WAS FROM THE SW. WE WERE GIVEN A TURN TO THE N TO FLY WHAT COULD BE CALLED A R DOWNWIND FOR RWY 18R. APPROX XING THE RIVER NBOUND, WE WERE GIVEN A DSCNT TO 2500 FT. AT FIRST I THOUGHT WE WOULD BE QUICKLY TURNED TOWARD THE ARPT. HOWEVER, AS WE CONTINUED NBOUND I MENTIONED TO THE CAPT MY DISCOMFORT WITH BEING VECTORED THROUGH THE CINCINNATI W (I67) TFC PATTERN AT 1900 FT AGL. WE WERE KEEPING A SHARP LOOKOUT FOR VFR TFC. SHORTLY AFTER BEING TURNED INTO THE LOC OUR TCASII ISSUED AN ADVISORY FOR TFC AT OUR 10 O'CLOCK AND LESS THAN A MI. THE CAPT DISCONNECTED THE AUTOPLT AND PUSHED THE NOSE OVER TO DSND. OUR TFC PASSED ALMOST DIRECTLY ABOVE US AT 150 FT SEPARATION. WHILE ALL THIS WAS HAPPENING. APCH CTL CALLED OUT THE TFC TELLING US THIS TFC HAD 'JUST POPPED UP.' I BELIEVE THIS TO BE TRUE AS THE TFC ALSO SUDDENLY APPEARED ON OUR TCASII. I RESPONDED TO THE CTLR WE HAD THE TFC IN SIGHT. I ALSO MENTIONED THE ALT READOUT ON THE TARGET OF 2600 FT WAS CORRECT, AND THAT THE ACFT WAS EITHER AN AZTEC OR A TWIN COMANCHE. AS THE TFC FLEW OVERHEAD I COULD TELL IT WAS A 1967 OR NEWER, BLUE AND WHITE TWIN COMANCHE WITH THE MILLER CONVERSION. THE PROB WITH THIS INCIDENT IS THE TWIN COMANCHE WAS LEGAL. THIS PERSON WAS FLYING OUTSIDE THE CLASS C AIRSPACE. MY SUGGESTION TO PREVENT A SIMILAR OCCURRENCE IS FOR CVG TRACON TO AVOID DSNDING TFC INBOUND TO CVG TOO SOON. I THINK SAFETY WOULD BE BETTER SERVED IF ACFT INBOUND WERE KEPT HIGHER -- ESPECIALLY OVER OTHER ARPTS IN CLOSE PROX TO THE CLASS C AIRSPACE. THE CINCINNATI/NORTHERN KENTUCKY INTL ARPT HAS EVOLVED INTO A VERY BUSY HUB FOR ACRS AND COMMUTERS. I THINK THE ARPT IS PUSHING THE LIMITS OF CLASS C PROTECTION. PERSONALLY, I DO NOT LIKE THE IDEA OF CLASS B AIRSPACE IF IT IS AT ALL POSSIBLE TO AVOID THE TAKING OF ADDITIONAL AIRSPACE. UNFORTUNATELY, I THINK MANY PLTS TRANSITIONING THE CVG AREA ARE UNAWARE OF JUST HOW BUSY THE CINCINNATI/NORTHERN KENTUCKY INTL ARPT HAS BECOME. PERHAPS THE TIME HAS COME FOR CONSIDERATION OF CLASS B AIRSPACE.

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.