B737 follows wrong aircraft on visual approach to mdw.

Attributes
ACN	602134
Time
Date	200312
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : c90.tracon tower : mdw.tower
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 180 flight time total : 10000 flight time type : 7500
ASRS Report	602134
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to original clearance
Miss Distance	horizontal : 15000 vertical : 1000
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

I was PF on last leg of 3 day trip into chicago midway. Approach called traffic at our 12:30-1 O'clock position. Aircraft reported in sight at 1 O'clock position. No other aircraft in view ahead or left of nose. Also, no other traffic displayed left off nose on TCASII 10 DME screen. I was cleared for visual approach and started to turn a wide right base behind aircraft sighted on final. At least a min later, approach said we were following the wrong aircraft. We sighted a second aircraft at our then 10 O'clock position and about 4 mi. The approach controller sounded upset. We made a slight left turn and fell in behind second aircraft for an uneventful landing. I think the controller made a mistake and called our traffic off the first aircraft when he meant the second aircraft. I will be more cautious in the future before accepting a visual approach.

Original NASA ASRS Text

Title: B737 FOLLOWS WRONG ACFT ON VISUAL APCH TO MDW.

Narrative: I WAS PF ON LAST LEG OF 3 DAY TRIP INTO CHICAGO MIDWAY. APCH CALLED TFC AT OUR 12:30-1 O'CLOCK POS. ACFT RPTED IN SIGHT AT 1 O'CLOCK POS. NO OTHER ACFT IN VIEW AHEAD OR L OF NOSE. ALSO, NO OTHER TFC DISPLAYED L OFF NOSE ON TCASII 10 DME SCREEN. I WAS CLRED FOR VISUAL APCH AND STARTED TO TURN A WIDE R BASE BEHIND ACFT SIGHTED ON FINAL. AT LEAST A MIN LATER, APCH SAID WE WERE FOLLOWING THE WRONG ACFT. WE SIGHTED A SECOND ACFT AT OUR THEN 10 O'CLOCK POS AND ABOUT 4 MI. THE APCH CTLR SOUNDED UPSET. WE MADE A SLIGHT L TURN AND FELL IN BEHIND SECOND ACFT FOR AN UNEVENTFUL LNDG. I THINK THE CTLR MADE A MISTAKE AND CALLED OUR TFC OFF THE FIRST ACFT WHEN HE MEANT THE SECOND ACFT. I WILL BE MORE CAUTIOUS IN THE FUTURE BEFORE ACCEPTING A VISUAL APCH.

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.