Air carrier X TCASII took evasive action from possible false target.

Attributes
ACN	247048
Time
Date	199307
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord tracon : mia
Operator	common carrier : air carrier
Make Model Name	Widebody Transport
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	247048
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 1800
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Air carrier X was 4 NM north of mdw and asked the controller if he showed any traffic 3 mi in front of him. The controller issued both targets he saw (1 at 900 ft MSL and 1 at 1600 ft MSL). Air carrier X said he showed a target with no mode C and wanted to turn right to avoid it. The controller approved the request. Air carrier X was in the TCA and said that there was a narrow cloud bank in front of him and thought the target might be behind it. There were no other targets observed in the area. The controller was not aware the aircraft was TCASII equipped.

Original NASA ASRS Text

Title: ACR X TCASII TOOK EVASIVE ACTION FROM POSSIBLE FALSE TARGET.

Narrative: ACR X WAS 4 NM N OF MDW AND ASKED THE CTLR IF HE SHOWED ANY TFC 3 MI IN FRONT OF HIM. THE CTLR ISSUED BOTH TARGETS HE SAW (1 AT 900 FT MSL AND 1 AT 1600 FT MSL). ACR X SAID HE SHOWED A TARGET WITH NO MODE C AND WANTED TO TURN R TO AVOID IT. THE CTLR APPROVED THE REQUEST. ACR X WAS IN THE TCA AND SAID THAT THERE WAS A NARROW CLOUD BANK IN FRONT OF HIM AND THOUGHT THE TARGET MIGHT BE BEHIND IT. THERE WERE NO OTHER TARGETS OBSERVED IN THE AREA. THE CTLR WAS NOT AWARE THE ACFT WAS TCASII EQUIPPED.

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.