Close proximity air carrier-medium large transport unk-aircraft at the base of mdw arsa.

Attributes
ACN	129560
Time
Date	198911
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mdw
State Reference	IL
Altitude	msl bound lower : 1800 msl bound upper : 1800
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : ord tower : mdw
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 16000
ASRS Report	129560
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : published procedure non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

During a left turn to a heading assigned after takeoff, from runway 31L at mdw, I saw an aircraft beacon above and to our left. This traffic was not given to us by the tower. I told departure control of the aircraft. He replied, 'it was an arsa violator. Tower did know of it.' my instruction to the PF was to 'shallow your bank (turn), so as to not turn into it.'

Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG UNK-ACFT AT THE BASE OF MDW ARSA.

Narrative: DURING A LEFT TURN TO A HDG ASSIGNED AFTER TKOF, FROM RWY 31L AT MDW, I SAW AN ACFT BEACON ABOVE AND TO OUR LEFT. THIS TFC WAS NOT GIVEN TO US BY THE TWR. I TOLD DEP CTL OF THE ACFT. HE REPLIED, 'IT WAS AN ARSA VIOLATOR. TWR DID KNOW OF IT.' MY INSTRUCTION TO THE PF WAS TO 'SHALLOW YOUR BANK (TURN), SO AS TO NOT TURN INTO IT.'

Data retrieved from NASA's ASRS site as of August 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.