F28 inbound to pdx has a conflict with an unknown VFR aircraft.

Attributes
ACN	471408
Time
Date	200004
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : pdx.airport
State Reference	AB
Altitude	msl single value : 4500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	F28 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	climbout : vacating altitude
Person 1
Affiliation	government : faa
Function	controller : approach instruction : instructor
Qualification	controller : radar
Experience	controller military : 4 controller radar : 12
ASRS Report	471408
Person 2
Function	controller : approach instruction : trainee
Qualification	controller : radar
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	other controllera other controllerb other flight crewa
Resolutory Action	controller : issued advisory
Miss Distance	horizontal : 3000 vertical : 100
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance Airspace Structure
Primary Problem	Ambiguous

Narrative:

Air carrier X, F28, a pdx arrival from the south descending for pdx. I observed a VFR aircraft Y climbing sebound opposite direction to the air carrier X. I told the trainee to issue the traffic he did and the pilot had the traffic in sight and told us that the altitude of the traffic was good at 4400 ft MSL. The air carrier X stopped at 4500 ft. The pilot of the air carrier X seemed surprised that they did not get a TCASII alert. The VFR aircraft Y never called for advisories and approximately 5 mins was a problem with another arrival. I estimated the closest that they got were 1/2 mi or less and 100 ft. While it was good that the traffic had a transponder with altitude encoding, I believe that if we had a class B airspace, at portland, or, this aircraft would have been required to call us, that this problem could have been avoided.

Original NASA ASRS Text

Title: F28 INBOUND TO PDX HAS A CONFLICT WITH AN UNKNOWN VFR ACFT.

Narrative: ACR X, F28, A PDX ARR FROM THE S DSNDING FOR PDX. I OBSERVED A VFR ACFT Y CLBING SEBOUND OPPOSITE DIRECTION TO THE ACR X. I TOLD THE TRAINEE TO ISSUE THE TFC HE DID AND THE PLT HAD THE TFC IN SIGHT AND TOLD US THAT THE ALT OF THE TFC WAS GOOD AT 4400 FT MSL. THE ACR X STOPPED AT 4500 FT. THE PLT OF THE ACR X SEEMED SURPRISED THAT THEY DID NOT GET A TCASII ALERT. THE VFR ACFT Y NEVER CALLED FOR ADVISORIES AND APPROX 5 MINS WAS A PROB WITH ANOTHER ARR. I ESTIMATED THE CLOSEST THAT THEY GOT WERE 1/2 MI OR LESS AND 100 FT. WHILE IT WAS GOOD THAT THE TFC HAD A XPONDER WITH ALT ENCODING, I BELIEVE THAT IF WE HAD A CLASS B AIRSPACE, AT PORTLAND, OR, THIS ACFT WOULD HAVE BEEN REQUIRED TO CALL US, THAT THIS PROB COULD HAVE BEEN AVOIDED.

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.