Medium large transport crew had an near midair collision. Crew followed TCASII RA.

Attributes
ACN	409564
Time
Date	199807
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bij airport : mdw
State Reference	MI
Altitude	msl bound lower : 10000 msl bound upper : 10300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Route In Use	departure other departure sid : sid enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 2300 flight time type : 1000
ASRS Report	409564
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 300 vertical : 100

Narrative:

Near miss occurred between airliner accelerating at 10000 ft and a small twin assumed VFR at 10500 ft. Pilots were trailing another airliner at 5 NM when PF noted pop up TCASII traffic. Pilots visually acquire VFR target between the 2ND airliner and initiated a descent to increase miss distance. TCASII then issued an RA instructing a 1500-2000 FPM climb. We complied and started a right turn setting up a left to left head on pass in order to increase miss distance. We passed +/- 300 ft apart and continued on our way. Thank you TCASII.

Original NASA ASRS Text

Title: MLG CREW HAD AN NMAC. CREW FOLLOWED TCASII RA.

Narrative: NEAR MISS OCCURRED BTWN AIRLINER ACCELERATING AT 10000 FT AND A SMALL TWIN ASSUMED VFR AT 10500 FT. PLTS WERE TRAILING ANOTHER AIRLINER AT 5 NM WHEN PF NOTED POP UP TCASII TFC. PLTS VISUALLY ACQUIRE VFR TARGET BTWN THE 2ND AIRLINER AND INITIATED A DSCNT TO INCREASE MISS DISTANCE. TCASII THEN ISSUED AN RA INSTRUCTING A 1500-2000 FPM CLB. WE COMPLIED AND STARTED A R TURN SETTING UP A L TO L HEAD ON PASS IN ORDER TO INCREASE MISS DISTANCE. WE PASSED +/- 300 FT APART AND CONTINUED ON OUR WAY. THANK YOU TCASII.

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.