A mooney M20 pilot descended below assigned altitude without a clearance west of 7b2.

Attributes
ACN	440600
Time
Date	199906
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : 7b2.airport
State Reference	MA
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw.artcc artcc : zbw.artcc
Operator	general aviation : personal
Make Model Name	M-20 L
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot oversight : pic
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 68 flight time total : 888 flight time type : 291
ASRS Report	440600
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to assigned airspace
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cruising at high altitude. I thought I was cleared to descend to 10000 ft. When at 10500 ft, controller asked if a realized my clearance was to 11000 ft. I immediately went back to 11000 ft.

Original NASA ASRS Text

Title: A MOONEY M20 PLT DSNDED BELOW ASSIGNED ALT WITHOUT A CLRNC W OF 7B2.

Narrative: CRUISING AT HIGH ALT. I THOUGHT I WAS CLRED TO DSND TO 10000 FT. WHEN AT 10500 FT, CTLR ASKED IF A REALIZED MY CLRNC WAS TO 11000 FT. I IMMEDIATELY WENT BACK TO 11000 FT.

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.