Reporter error admitted in altitude deviation altitude excursion.

Attributes
ACN	301291
Time
Date	199504
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dtw
State Reference	MI
Altitude	msl bound lower : 9000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dtw
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Route In Use	arrival other arrival star : star enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time type : 75
ASRS Report	301291
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 12000 flight time type : 2340
ASRS Report	301292
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Another altitude bust caused by similar call signs and the approach controller's failure to catch our readback. We were on the cetus arrival into dtw runway 21R, level at 12000 ft. Our call sign was yyz and there was an xyz on the frequency, also. We evidently took a heading and altitude change that was meant for xyz. We descended to 9000 ft and were level for several mins before the approach controller noticed the mistake and told us to climb up to 11000 ft. He changed that to 10000 ft after the climb was started. There was no conflict, that I know of, with other aircraft. Evidently the controller missed our readback or it was blocked. Similar call signs on the same frequency during busy hub times are still a big problem for both pilots and controllers. Supplemental information from acn 301292: just before gloze, we were given 'turn left to 300 degrees and descend to 9000 ft.' we read back 'left 300 degrees down to 9000 ft.' we received an acknowledgement and I repeated 300 degrees down to 9000 ft. I said we read back 300 degrees and 9000 ft and controller said it was blocked.

Original NASA ASRS Text

Title: RPTR ERROR ADMITTED IN ALTDEV ALT EXCURSION.

Narrative: ANOTHER ALT BUST CAUSED BY SIMILAR CALL SIGNS AND THE APCH CTLR'S FAILURE TO CATCH OUR READBACK. WE WERE ON THE CETUS ARR INTO DTW RWY 21R, LEVEL AT 12000 FT. OUR CALL SIGN WAS YYZ AND THERE WAS AN XYZ ON THE FREQ, ALSO. WE EVIDENTLY TOOK A HDG AND ALT CHANGE THAT WAS MEANT FOR XYZ. WE DSNDED TO 9000 FT AND WERE LEVEL FOR SEVERAL MINS BEFORE THE APCH CTLR NOTICED THE MISTAKE AND TOLD US TO CLB UP TO 11000 FT. HE CHANGED THAT TO 10000 FT AFTER THE CLB WAS STARTED. THERE WAS NO CONFLICT, THAT I KNOW OF, WITH OTHER ACFT. EVIDENTLY THE CTLR MISSED OUR READBACK OR IT WAS BLOCKED. SIMILAR CALL SIGNS ON THE SAME FREQ DURING BUSY HUB TIMES ARE STILL A BIG PROB FOR BOTH PLTS AND CTLRS. SUPPLEMENTAL INFO FROM ACN 301292: JUST BEFORE GLOZE, WE WERE GIVEN 'TURN L TO 300 DEGS AND DSND TO 9000 FT.' WE READ BACK 'L 300 DEGS DOWN TO 9000 FT.' WE RECEIVED AN ACKNOWLEDGEMENT AND I REPEATED 300 DEGS DOWN TO 9000 FT. I SAID WE READ BACK 300 DEGS AND 9000 FT AND CTLR SAID IT WAS BLOCKED.

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.