B757 inbound to phl takes evasive action from unknown traffic.

Attributes
ACN	580134
Time
Date	200303
Day	Wed
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : phl.airport
State Reference	PA
Altitude	msl bound lower : 3700 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : phl.tracon
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach descent : intermediate altitude
Route In Use	approach : visual arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : phl.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise : level
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 8000 flight time type : 2000
ASRS Report	580134
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
ASRS Report	580337
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other spatial deviation
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous
Air Traffic Incident	Pilot Deviation

Narrative:

We were being vectored for runway 9L at phl. We were at 4000 ft, heading 210 degrees assigned. At this point, I saw what appeared to be very close traffic out the right window. It appeared to be very close and closing on us rapidly at the same altitude. Approach control was talking to other traffic, so there wasn't time to query him concerning conflict. I shouted out 'traffic' several times to the captain, then took evasive action. I disengaged the autoplt and turned approximately 90 degrees to the left and lost 300 ft of altitude. The captain advised ATC that we were avoiding traffic on our right side. The controller reported no traffic near us. The controller then gave clearance to descend to 3000 ft and fly heading 240 degrees, which we complied with. The remainder of the approach and landing were uneventful. Supplemental information from acn 580337: the controller reported he saw no traffic on our right side near our aircraft. There was no RA or TA from the TCASII which was operating normally. The controller instructed us to continue descent to 3000 ft from 3700 ft and fly a heading of 240 degrees to continue the downwind. The entire deviation episode lasted about 15 seconds.

Original NASA ASRS Text

Title: B757 INBOUND TO PHL TAKES EVASIVE ACTION FROM UNKNOWN TFC.

Narrative: WE WERE BEING VECTORED FOR RWY 9L AT PHL. WE WERE AT 4000 FT, HDG 210 DEGS ASSIGNED. AT THIS POINT, I SAW WHAT APPEARED TO BE VERY CLOSE TFC OUT THE R WINDOW. IT APPEARED TO BE VERY CLOSE AND CLOSING ON US RAPIDLY AT THE SAME ALT. APCH CTL WAS TALKING TO OTHER TFC, SO THERE WASN'T TIME TO QUERY HIM CONCERNING CONFLICT. I SHOUTED OUT 'TFC' SEVERAL TIMES TO THE CAPT, THEN TOOK EVASIVE ACTION. I DISENGAGED THE AUTOPLT AND TURNED APPROX 90 DEGS TO THE L AND LOST 300 FT OF ALT. THE CAPT ADVISED ATC THAT WE WERE AVOIDING TFC ON OUR R SIDE. THE CTLR RPTED NO TFC NEAR US. THE CTLR THEN GAVE CLRNC TO DSND TO 3000 FT AND FLY HDG 240 DEGS, WHICH WE COMPLIED WITH. THE REMAINDER OF THE APCH AND LNDG WERE UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 580337: THE CTLR RPTED HE SAW NO TFC ON OUR R SIDE NEAR OUR ACFT. THERE WAS NO RA OR TA FROM THE TCASII WHICH WAS OPERATING NORMALLY. THE CTLR INSTRUCTED US TO CONTINUE DSCNT TO 3000 FT FROM 3700 FT AND FLY A HDG OF 240 DEGS TO CONTINUE THE DOWNWIND. THE ENTIRE DEV EPISODE LASTED ABOUT 15 SECONDS.

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.