Close proximity air carrier-medium large transport GA-small aircraft near ord TCA mdw arsa.

Attributes
ACN	95143
Time
Date	198809
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cgt airport : ord
State Reference	IL
Altitude	msl bound lower : 3400 msl bound upper : 3400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	cruise other
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 165 flight time total : 13000 flight time type : 980
ASRS Report	95143
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 250 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While on chicago approach frequency on a heading of 270 degrees, was given a clearance to descend from 5000 to 3000'. We were given a frequency change at that same time or shortly after starting descent. After changing frequencys I saw traffic just to the left of 12 O'clock and level, about 1/2 mi away and coming towards us. The traffic was a single engine, low wing, aircraft apparently cruising at 3500' MSL. I pointed out the traffic to captain, who was flying, and I put my hands on the yoke to take control if required. The captain saw the traffic immediately and started a bank to the right as traffic passed on our left as we passed about 3400' MSL. After checking in on frequency we learned that the traffic was VFR on radar advisory with this same controller. Contributing factors: we were given a descent through an altitude where there was known conflicting traffic, who was talking to the same controling agency (different frequency). We were never issued a traffic advisory or given an avoidance vector. Visibility was reduced heading west due to setting sun and haze. Chicago approach control was unusually busy this pm. Note: I made a near miss report to chicago approach control. Area supervisor took the report.

Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG GA-SMA NEAR ORD TCA MDW ARSA.

Narrative: WHILE ON CHICAGO APCH FREQ ON A HDG OF 270 DEGS, WAS GIVEN A CLRNC TO DSND FROM 5000 TO 3000'. WE WERE GIVEN A FREQ CHANGE AT THAT SAME TIME OR SHORTLY AFTER STARTING DSCNT. AFTER CHANGING FREQS I SAW TFC JUST TO THE LEFT OF 12 O'CLOCK AND LEVEL, ABOUT 1/2 MI AWAY AND COMING TOWARDS US. THE TFC WAS A SINGLE ENG, LOW WING, ACFT APPARENTLY CRUISING AT 3500' MSL. I POINTED OUT THE TFC TO CAPT, WHO WAS FLYING, AND I PUT MY HANDS ON THE YOKE TO TAKE CTL IF REQUIRED. THE CAPT SAW THE TFC IMMEDIATELY AND STARTED A BANK TO THE RIGHT AS TFC PASSED ON OUR LEFT AS WE PASSED ABOUT 3400' MSL. AFTER CHKING IN ON FREQ WE LEARNED THAT THE TFC WAS VFR ON RADAR ADVISORY WITH THIS SAME CTLR. CONTRIBUTING FACTORS: WE WERE GIVEN A DSCNT THROUGH AN ALT WHERE THERE WAS KNOWN CONFLICTING TFC, WHO WAS TALKING TO THE SAME CTLING AGENCY (DIFFERENT FREQ). WE WERE NEVER ISSUED A TFC ADVISORY OR GIVEN AN AVOIDANCE VECTOR. VIS WAS REDUCED HDG W DUE TO SETTING SUN AND HAZE. CHICAGO APCH CTL WAS UNUSUALLY BUSY THIS PM. NOTE: I MADE A NEAR MISS RPT TO CHICAGO APCH CTL. AREA SUPVR TOOK THE RPT.

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.