Air carrier X TCASII RA descent from unknown traffic possible false target.

Attributes
ACN	231987
Time
Date	199301
Day	Sun
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
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord tracon : mob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	231987
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Air carrier X on runway 14R localizer said he had TCASII RA to descend reference traffic at 4 O'clock. The controller did not know what traffic the pilot was referring to. The pilot said he started to descend then he stopped. There was a clearance deviation by the aircraft of 100 ft. Communication was initiated by the TCASII aircraft. However, it was after the maneuver. The TCASII was disruptive to the controller's plans in a way that it was disruptive to traffic flow while he was explaining what happened on frequency.

Original NASA ASRS Text

Title: ACR X TCASII RA DSCNT FROM UNKNOWN TFC POSSIBLE FALSE TARGET.

Narrative: ACR X ON RWY 14R LOC SAID HE HAD TCASII RA TO DSND REF TFC AT 4 O'CLOCK. THE CTLR DID NOT KNOW WHAT TFC THE PLT WAS REFERRING TO. THE PLT SAID HE STARTED TO DSND THEN HE STOPPED. THERE WAS A CLRNC DEV BY THE ACFT OF 100 FT. COM WAS INITIATED BY THE TCASII ACFT. HOWEVER, IT WAS AFTER THE MANEUVER. THE TCASII WAS DISRUPTIVE TO THE CTLR'S PLANS IN A WAY THAT IT WAS DISRUPTIVE TO TFC FLOW WHILE HE WAS EXPLAINING WHAT HAPPENED ON FREQ.

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.