A VFR aircraft passed in front of air carrier aircraft which resulted in a near midair collision.

Attributes
ACN	151145
Time
Date	199007
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : aml airport : iad
State Reference	VA
Altitude	msl bound lower : 6500 msl bound upper : 6500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : iad tower : phl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	151145
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 4200 flight time type : 400
ASRS Report	152208
Events
Anomaly	conflict : nmac non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : insufficient time
Consequence	faa : reviewed incident with flight crew faa : investigated
Miss Distance	vertical : 450
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Large transport was vectored for a right downwind for runway 1R at iad, descended to 5000'. Large transport advised of a near mid-air. After being advised, I observed a primary target pass nwbnd then observed aircraft transponder on a VFR code. Aircraft then contacted me for identifying flight following to agc. Large transport filed a near midair collision report with iad approach control's area manager.

Original NASA ASRS Text

Title: A VFR ACFT PASSED IN FRONT OF ACR ACFT WHICH RESULTED IN A NMAC.

Narrative: LGT WAS VECTORED FOR A R DOWNWIND FOR RWY 1R AT IAD, DSNDED TO 5000'. LGT ADVISED OF A NEAR MID-AIR. AFTER BEING ADVISED, I OBSERVED A PRIMARY TARGET PASS NWBND THEN OBSERVED ACFT XPONDER ON A VFR CODE. ACFT THEN CONTACTED ME FOR IDENTIFYING FLT FOLLOWING TO AGC. LGT FILED A NMAC RPT WITH IAD APCH CTL'S AREA MGR.

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.