Narrative:

While talking to ZOB at 12000 ft, I requested lower. Controller asked how much lower. I responded 6000 ft. He acknowledged the request with I believe 'roger.' I took that to mean 6000 ft was approved. At 10600 ft in my descent, the controller asked what my altitude was. I responded '10600 ft descending to 6000 ft.' he said I was not cleared to 6000 ft and remain at 11000 ft. I climbed to 11000 ft and remained there until after handoff to erie approach.

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Original NASA ASRS Text

Title: PLT DEVIATED FROM IFR CLRNC WHEN HE DEPARTED FROM ASSIGNED ALT IN ZOB AIRSPACE.

Narrative: WHILE TALKING TO ZOB AT 12000 FT, I REQUESTED LOWER. CTLR ASKED HOW MUCH LOWER. I RESPONDED 6000 FT. HE ACKNOWLEDGED THE REQUEST WITH I BELIEVE 'ROGER.' I TOOK THAT TO MEAN 6000 FT WAS APPROVED. AT 10600 FT IN MY DSCNT, THE CTLR ASKED WHAT MY ALT WAS. I RESPONDED '10600 FT DSNDING TO 6000 FT.' HE SAID I WAS NOT CLRED TO 6000 FT AND REMAIN AT 11000 FT. I CLBED TO 11000 FT AND REMAINED THERE UNTIL AFTER HDOF TO ERIE 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.