Narrative:

Beautiful afternoon. Lots of targets on the TCASII. I mentioned it to the captain about 5-10 mins before the incident. We were handed off to flint approach and cleared down to 4000 ft from 8000 ft about 30 NM from the airport. I was off frequency for 30 seconds to call in-range to company and when I came back we had been cleared to 3000 ft. I noticed a target on TCASII, 12 O'clock, 6 mi and 700 ft below our altitude of 4200 ft. I asked the captain if he had that traffic. He didn't and continued to descend while we looked. The frequency was very busy and the controller was trying to cope with all the traffic and didn't seem concerned he had cleared us through the VFR traffic's altitude. I thought the captain might level off or increase the rate of descent to better avoid the traffic but he did not. Looking back I should have voiced my concern to either the captain or the controller or both but I didn't. When we reached about 3700 ft and 1 mi from the traffic, the controller asked if we had him in sight. I said negative. The controller gave us a vector and the VFR traffic reported us in sight. I finally saw him about 200 ft below and 1/2 - 3/4 mi off the wing. I think the controller was overloaded with all the traffic and didn't see the conflict. We didn't want to deviate from our clearance despite the TCASII indication.

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Original NASA ASRS Text

Title: A DSNDING BE02 HAS A TARGET ON THEIR TCASI OR TCASII BUT KEEPS DSNDING TOWARDS AND THROUGH THE VFR C150'S ALT. FO RPTR ACTS REPENTANT OVER HIS FAILURE TO SAY ANYTHING TO ATC OR THE PIC.

Narrative: BEAUTIFUL AFTERNOON. LOTS OF TARGETS ON THE TCASII. I MENTIONED IT TO THE CAPT ABOUT 5-10 MINS BEFORE THE INCIDENT. WE WERE HANDED OFF TO FLINT APCH AND CLRED DOWN TO 4000 FT FROM 8000 FT ABOUT 30 NM FROM THE ARPT. I WAS OFF FREQ FOR 30 SECONDS TO CALL IN-RANGE TO COMPANY AND WHEN I CAME BACK WE HAD BEEN CLRED TO 3000 FT. I NOTICED A TARGET ON TCASII, 12 O'CLOCK, 6 MI AND 700 FT BELOW OUR ALT OF 4200 FT. I ASKED THE CAPT IF HE HAD THAT TFC. HE DIDN'T AND CONTINUED TO DSND WHILE WE LOOKED. THE FREQ WAS VERY BUSY AND THE CTLR WAS TRYING TO COPE WITH ALL THE TFC AND DIDN'T SEEM CONCERNED HE HAD CLRED US THROUGH THE VFR TFC'S ALT. I THOUGHT THE CAPT MIGHT LEVEL OFF OR INCREASE THE RATE OF DSCNT TO BETTER AVOID THE TFC BUT HE DID NOT. LOOKING BACK I SHOULD HAVE VOICED MY CONCERN TO EITHER THE CAPT OR THE CTLR OR BOTH BUT I DIDN'T. WHEN WE REACHED ABOUT 3700 FT AND 1 MI FROM THE TFC, THE CTLR ASKED IF WE HAD HIM IN SIGHT. I SAID NEGATIVE. THE CTLR GAVE US A VECTOR AND THE VFR TFC RPTED US IN SIGHT. I FINALLY SAW HIM ABOUT 200 FT BELOW AND 1/2 - 3/4 MI OFF THE WING. I THINK THE CTLR WAS OVERLOADED WITH ALL THE TFC AND DIDN'T SEE THE CONFLICT. WE DIDN'T WANT TO DEVIATE FROM OUR CLRNC DESPITE THE TCASII INDICATION.

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.