A DC9 captain reported an near midair collision on the cetus arrival to dtw.

Attributes
ACN	512340
Time
Date	200105
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	intersection : cetus
State Reference	OH
Altitude	msl single value : 11000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : vgt.tower
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Flight Phase	cruise : level
Route In Use	arrival star : cetus
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : d21.tracon
Operator	common carrier : air carrier
Make Model Name	Airbus Industrie Undifferentiated or Other Model
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 190 flight time total : 10000 flight time type : 6000
ASRS Report	512340
Events
Anomaly	conflict : nmac non adherence : published procedure
Resolutory Action	flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Deviation

Narrative:

In cruise at 11000 ft MSL, northwest of cetus intersection on cetus arrival (STAR), noticed an air carrier airbus descending from above and behind my aircraft at approximately 5 O'clock position. Received a TA from TCASII. As I was adjusting TCASII range scale to 5 NM to better analyze situation, I received (simultaneously) an RA to descend and a left turn from ATC of approximately 70 degrees magnitude. Knowing the closure was from above and to my right rear, I immediately rolled into an approximately 45 degree banked left descending turn of approximately 400 FPM. I changed direction quickly and had only descended 250 ft when the RA ceased and the event was over. Dtw metropolitan TRACON asked me to call them on the ground. The watch supervisor said they had received a conflict alert on the 2 aircraft in question. He said the other air carrier had received an RA and was curious as to whether we had. He believed the problem was with a ZOB controller.

Original NASA ASRS Text

Title: A DC9 CAPT RPTED AN NMAC ON THE CETUS ARR TO DTW.

Narrative: IN CRUISE AT 11000 FT MSL, NW OF CETUS INTXN ON CETUS ARR (STAR), NOTICED AN ACR AIRBUS DSNDING FROM ABOVE AND BEHIND MY ACFT AT APPROX 5 O'CLOCK POS. RECEIVED A TA FROM TCASII. AS I WAS ADJUSTING TCASII RANGE SCALE TO 5 NM TO BETTER ANALYZE SIT, I RECEIVED (SIMULTANEOUSLY) AN RA TO DSND AND A L TURN FROM ATC OF APPROX 70 DEGS MAGNITUDE. KNOWING THE CLOSURE WAS FROM ABOVE AND TO MY R REAR, I IMMEDIATELY ROLLED INTO AN APPROX 45 DEG BANKED L DSNDING TURN OF APPROX 400 FPM. I CHANGED DIRECTION QUICKLY AND HAD ONLY DSNDED 250 FT WHEN THE RA CEASED AND THE EVENT WAS OVER. DTW METRO TRACON ASKED ME TO CALL THEM ON THE GND. THE WATCH SUPVR SAID THEY HAD RECEIVED A CONFLICT ALERT ON THE 2 ACFT IN QUESTION. HE SAID THE OTHER ACR HAD RECEIVED AN RA AND WAS CURIOUS AS TO WHETHER WE HAD. HE BELIEVED THE PROB WAS WITH A ZOB CTLR.

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.