Narrative:

While trying to remain VFR on top of cloud layers, while on an IFR flight plan, I was unable to climb fast enough to clear a newly encountered cloud deck. I entered clouds at 8000' and immediately began picking up ice. At 9500' MSL, I could no longer climb and headed west, 270 degree, over the ocean and descended. While passing through 6000', the ice started sloughing off the windscreen. I leveled at 5000' and turned to go direct fot. When I advised center I was ok they told me my last assigned altitude was 11000' (then changed it to 9000') with a minimum vector altitude of 6000' and I'm at 5000'. 'What are your intentions?' I distinctly remember a clearance to 5000' once I told the center I was descending so am at a loss to understand what they were telling me. I asked how much longer along my present course it would be before I could maintain a lower IFR altitude than 6000'. The answer I got I didn't understand. At some point in the conversation with ZOA I told them I was climbing back to 6000'. They handed me off to seattle before I got there and seattle cleared me to stay at 5600' or 5700' until I could descend into fot. When I first got the ice in the clouds I was going to turn back; but a company aircraft advised me he was in the clear at a higher altitude. Had I turned back immediately, this would not have happened. The ice build up was more rapid than I have experienced in nearly 30 yrs of flying.

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Original NASA ASRS Text

Title: PLT OF SMT TWIN ATX ON IFR PLAN EXCURSIONED FROM ASSIGNED ALT TOO FREQUENT FOR ARTCC CTLR TO KEEP TRACK OF HIM.

Narrative: WHILE TRYING TO REMAIN VFR ON TOP OF CLOUD LAYERS, WHILE ON AN IFR FLT PLAN, I WAS UNABLE TO CLB FAST ENOUGH TO CLR A NEWLY ENCOUNTERED CLOUD DECK. I ENTERED CLOUDS AT 8000' AND IMMEDIATELY BEGAN PICKING UP ICE. AT 9500' MSL, I COULD NO LONGER CLB AND HEADED W, 270 DEG, OVER THE OCEAN AND DSNDED. WHILE PASSING THROUGH 6000', THE ICE STARTED SLOUGHING OFF THE WINDSCREEN. I LEVELED AT 5000' AND TURNED TO GO DIRECT FOT. WHEN I ADVISED CENTER I WAS OK THEY TOLD ME MY LAST ASSIGNED ALT WAS 11000' (THEN CHANGED IT TO 9000') WITH A MINIMUM VECTOR ALT OF 6000' AND I'M AT 5000'. 'WHAT ARE YOUR INTENTIONS?' I DISTINCTLY REMEMBER A CLRNC TO 5000' ONCE I TOLD THE CENTER I WAS DSNDING SO AM AT A LOSS TO UNDERSTAND WHAT THEY WERE TELLING ME. I ASKED HOW MUCH LONGER ALONG MY PRESENT COURSE IT WOULD BE BEFORE I COULD MAINTAIN A LOWER IFR ALT THAN 6000'. THE ANSWER I GOT I DIDN'T UNDERSTAND. AT SOME POINT IN THE CONVERSATION WITH ZOA I TOLD THEM I WAS CLBING BACK TO 6000'. THEY HANDED ME OFF TO SEATTLE BEFORE I GOT THERE AND SEATTLE CLRED ME TO STAY AT 5600' OR 5700' UNTIL I COULD DSND INTO FOT. WHEN I FIRST GOT THE ICE IN THE CLOUDS I WAS GOING TO TURN BACK; BUT A COMPANY ACFT ADVISED ME HE WAS IN THE CLR AT A HIGHER ALT. HAD I TURNED BACK IMMEDIATELY, THIS WOULD NOT HAVE HAPPENED. THE ICE BUILD UP WAS MORE RAPID THAN I HAVE EXPERIENCED IN NEARLY 30 YRS OF FLYING.

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.