A B737-300 flight crew accepts a climb clearance meant for another aircraft and is turned off course and asked to descend when ATC becomes aware of the altitude deviation 71 mi east of crl, mi.

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Attributes
ACN	468968
Time
Date	200004
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : crl.vortac
State Reference	MI
Altitude	msl bound lower : 33000 msl bound upper : 34700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob.artcc tower : gmu.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	cruise : enroute altitude change
Route In Use	enroute airway : ns.airway
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute airway : ns.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 304 flight time total : 19581 flight time type : 11491
ASRS Report	468968
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance controller : separated traffic flight crew : returned to assigned altitude
Miss Distance	horizontal : 36000 vertical : 300
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

In cruise flight at FL330, ZOB (133.37) cleared us to FL350. FL350 was read back and we started the climb. At approximately 34700 ft ZOB asked our altitude. When we read back 34700 ft, cle said descend immediately to FL330 and then turn right. ZOB said we accepted someone else's clearance to FL350. The first officer and myself are quite sure cle cleared us to FL350, as we read it back, set FL350 in the altitude window and both of us verified FL350. There was no traffic conflict and after approximately 8-10 mins we were cleared back to FL350. Cle handed us off to next controller and said, 'thanks for the help.' the controller said that he never heard our readback to climb to FL350. I believe this event occurred due to the lack of communication. If we did accept someone else's altitude change then when we read it back, the controller should have caught the error, however, they are sometimes overloaded or the radio frequency may be blocked. The controller did see the altitude change and corrected it -- this is good. Also TCASII is a great safety device as it will show a pending traffic conflict. There cannot be enough verifying and confirming when there are altitude changes involved.

Original NASA ASRS Text

Title: A B737-300 FLC ACCEPTS A CLB CLRNC MEANT FOR ANOTHER ACFT AND IS TURNED OFF COURSE AND ASKED TO DSND WHEN ATC BECOMES AWARE OF THE ALTDEV 71 MI E OF CRL, MI.

Narrative: IN CRUISE FLT AT FL330, ZOB (133.37) CLRED US TO FL350. FL350 WAS READ BACK AND WE STARTED THE CLB. AT APPROX 34700 FT ZOB ASKED OUR ALT. WHEN WE READ BACK 34700 FT, CLE SAID DSND IMMEDIATELY TO FL330 AND THEN TURN R. ZOB SAID WE ACCEPTED SOMEONE ELSE'S CLRNC TO FL350. THE FO AND MYSELF ARE QUITE SURE CLE CLRED US TO FL350, AS WE READ IT BACK, SET FL350 IN THE ALT WINDOW AND BOTH OF US VERIFIED FL350. THERE WAS NO TFC CONFLICT AND AFTER APPROX 8-10 MINS WE WERE CLRED BACK TO FL350. CLE HANDED US OFF TO NEXT CTLR AND SAID, 'THANKS FOR THE HELP.' THE CTLR SAID THAT HE NEVER HEARD OUR READBACK TO CLB TO FL350. I BELIEVE THIS EVENT OCCURRED DUE TO THE LACK OF COM. IF WE DID ACCEPT SOMEONE ELSE'S ALT CHANGE THEN WHEN WE READ IT BACK, THE CTLR SHOULD HAVE CAUGHT THE ERROR, HOWEVER, THEY ARE SOMETIMES OVERLOADED OR THE RADIO FREQ MAY BE BLOCKED. THE CTLR DID SEE THE ALT CHANGE AND CORRECTED IT -- THIS IS GOOD. ALSO TCASII IS A GREAT SAFETY DEVICE AS IT WILL SHOW A PENDING TFC CONFLICT. THERE CANNOT BE ENOUGH VERIFYING AND CONFIRMING WHEN THERE ARE ALT CHANGES INVOLVED.

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.