Narrative:

The approach controller required the PA32 through the departure corridor for a right downwind for runway 18; which I approved. The PA32 came onto my frequency; and I told him to fly northbound for a wide right downwind for runway 18; and a beech jet would depart runway 24 and turn sbound. I cleared the beech jet for takeoff on runway 24; with a turn direct bae VOR (approximately a 180 degree heading). As soon as he started his turn; I pointed out the PA32 as 4 mi southwest of the airport descending out of 4000 ft. I also pointed out the BE40 to the saratoga; again stating that he was off the departure end of runway 24 and turning sbound. Neither aircraft had the other in sight. I had both aircraft in sight. The BE40's secondary target never tagged up on the tower radar; so I told him that I was not receiving his transponder. Out the window; he appeared to be turning away from the PA32 and still below him. After a few seconds; the BE40 tagged up approximately 1 mi northeast of the PA32 and 700 ft below him. The conflict alert went off immediately. I pointed out the PA32 again to the BE40; who said he had the traffic in sight. I told him to maintain visual separation with the traffic and to contact departure. The PA32 never reported the BE40 in sight or mentioned anything about him being a factor. After I got off position; the radar controller told me that the BE40 pilot had complained about how close he was to the PA32. The radar controller asked if he had the PA32 in sight when he passed it; and he replied 'affirmative.' I do not believe the aircraft were in an unsafe proximity to one another as the BE40 was turning to the south and restr to 3000 ft and the PA32 was on a high; wide downwind. The climb rate of the BE40 caused the conflict alert to activate. Conflict alerts activate routinely; despite aircraft having the legal radar separation; because of aircraft climb/descent rates. In this case; because I was applying visual separation; the aircraft we allowed to get within 500 or so feet of each other vertically and about 1 mi laterally; and the conflict alert activated. At no time did the primary radar targets merge. Looking back; I should have either delayed the departure of the BE40; or canceled the approach clearance of the PA32; and vectored him away from the flight path of the BE40; since he was still well above the MVA. An even better decision would have been not to approve the PA32 through the departure corridor in the first place.

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Original NASA ASRS Text

Title: GRB LOCAL CONTROLLER DESCRIBED CONFLICT WHEN ARRIVAL WAS VECTORED THROUGH DEPARTURE CORRIDOR; VISUAL SEPARATION PROCEDURES WERE APPLIED.

Narrative: THE APCH CTLR REQUIRED THE PA32 THROUGH THE DEP CORRIDOR FOR A R DOWNWIND FOR RWY 18; WHICH I APPROVED. THE PA32 CAME ONTO MY FREQ; AND I TOLD HIM TO FLY NBOUND FOR A WIDE R DOWNWIND FOR RWY 18; AND A BEECH JET WOULD DEPART RWY 24 AND TURN SBOUND. I CLRED THE BEECH JET FOR TKOF ON RWY 24; WITH A TURN DIRECT BAE VOR (APPROX A 180 DEG HDG). AS SOON AS HE STARTED HIS TURN; I POINTED OUT THE PA32 AS 4 MI SW OF THE ARPT DSNDING OUT OF 4000 FT. I ALSO POINTED OUT THE BE40 TO THE SARATOGA; AGAIN STATING THAT HE WAS OFF THE DEP END OF RWY 24 AND TURNING SBOUND. NEITHER ACFT HAD THE OTHER IN SIGHT. I HAD BOTH ACFT IN SIGHT. THE BE40'S SECONDARY TARGET NEVER TAGGED UP ON THE TWR RADAR; SO I TOLD HIM THAT I WAS NOT RECEIVING HIS XPONDER. OUT THE WINDOW; HE APPEARED TO BE TURNING AWAY FROM THE PA32 AND STILL BELOW HIM. AFTER A FEW SECONDS; THE BE40 TAGGED UP APPROX 1 MI NE OF THE PA32 AND 700 FT BELOW HIM. THE CONFLICT ALERT WENT OFF IMMEDIATELY. I POINTED OUT THE PA32 AGAIN TO THE BE40; WHO SAID HE HAD THE TFC IN SIGHT. I TOLD HIM TO MAINTAIN VISUAL SEPARATION WITH THE TFC AND TO CONTACT DEP. THE PA32 NEVER RPTED THE BE40 IN SIGHT OR MENTIONED ANYTHING ABOUT HIM BEING A FACTOR. AFTER I GOT OFF POS; THE RADAR CTLR TOLD ME THAT THE BE40 PLT HAD COMPLAINED ABOUT HOW CLOSE HE WAS TO THE PA32. THE RADAR CTLR ASKED IF HE HAD THE PA32 IN SIGHT WHEN HE PASSED IT; AND HE REPLIED 'AFFIRMATIVE.' I DO NOT BELIEVE THE ACFT WERE IN AN UNSAFE PROX TO ONE ANOTHER AS THE BE40 WAS TURNING TO THE S AND RESTR TO 3000 FT AND THE PA32 WAS ON A HIGH; WIDE DOWNWIND. THE CLB RATE OF THE BE40 CAUSED THE CONFLICT ALERT TO ACTIVATE. CONFLICT ALERTS ACTIVATE ROUTINELY; DESPITE ACFT HAVING THE LEGAL RADAR SEPARATION; BECAUSE OF ACFT CLB/DSCNT RATES. IN THIS CASE; BECAUSE I WAS APPLYING VISUAL SEPARATION; THE ACFT WE ALLOWED TO GET WITHIN 500 OR SO FEET OF EACH OTHER VERTLY AND ABOUT 1 MI LATERALLY; AND THE CONFLICT ALERT ACTIVATED. AT NO TIME DID THE PRIMARY RADAR TARGETS MERGE. LOOKING BACK; I SHOULD HAVE EITHER DELAYED THE DEP OF THE BE40; OR CANCELED THE APCH CLRNC OF THE PA32; AND VECTORED HIM AWAY FROM THE FLT PATH OF THE BE40; SINCE HE WAS STILL WELL ABOVE THE MVA. AN EVEN BETTER DECISION WOULD HAVE BEEN NOT TO APPROVE THE PA32 THROUGH THE DEP CORRIDOR IN THE FIRST PLACE.

Data retrieved from NASA's ASRS site as of May 2009 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.