Medium large transport has TCASII RA, takes evasive action.

Attributes
ACN	276550
Time
Date	199407
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : phl
State Reference	PA
Altitude	msl bound lower : 3000 msl bound upper : 3600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phl
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	arrival other arrival star : star enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	276550
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

On arrival to phl, we were level at 3000 ft approximately on a 15 mi base and were advised of VFR traffic level at 2500 ft. He passed very slightly left of our aircraft 500 ft below which caused a TCASII climb RA. We climbed 600 ft before given the clear of conflict then descended back to our assigned altitude. There were no conflicts other than the TCASII alert and ATC was surprised that we climbed when the traffic was pointed out at his assigned altitude below.

Original NASA ASRS Text

Title: MLG HAS TCASII RA, TAKES EVASIVE ACTION.

Narrative: ON ARR TO PHL, WE WERE LEVEL AT 3000 FT APPROX ON A 15 MI BASE AND WERE ADVISED OF VFR TFC LEVEL AT 2500 FT. HE PASSED VERY SLIGHTLY L OF OUR ACFT 500 FT BELOW WHICH CAUSED A TCASII CLB RA. WE CLBED 600 FT BEFORE GIVEN THE CLR OF CONFLICT THEN DSNDED BACK TO OUR ASSIGNED ALT. THERE WERE NO CONFLICTS OTHER THAN THE TCASII ALERT AND ATC WAS SURPRISED THAT WE CLBED WHEN THE TFC WAS POINTED OUT AT HIS ASSIGNED ALT BELOW.

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.