A GA light twin pilot was unable to maintain assigned altitude because of severe airframe icing.

Attributes
ACN	788479
Time
Date	200802
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : sea.airport
State Reference	WA
Altitude	msl bound lower : 10000 msl single value : 14000
Environment
Flight Conditions	IMC
Weather Elements	Ice
Light	Night
Aircraft 1
Controlling Facilities	tracon : s46.tracon
Operator	common carrier : air carrier
Make Model Name	Small Aircraft Low Wing 2 Eng Retractable Gear
Operating Under FAR Part	Part 135
Flight Phase	descent : approach
Route In Use	arrival star : eph6
Person 1
Affiliation	company : air carrier
Function	flight crew : single pilot
Qualification	pilot : multi engine pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 3000 flight time type : 1000
ASRS Report	788479
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter other non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	none taken : unable
Supplementary
Problem Areas	Weather
Primary Problem	Weather

Narrative:

Was assigned to cross flaak intersection at 11000 ft and then descend down to 10000 ft. Was not able to maintain assigned 10000 ft due to severe aircraft structural icing.

Original NASA ASRS Text

Title: A GA LIGHT TWIN PILOT WAS UNABLE TO MAINTAIN ASSIGNED ALT BECAUSE OF SEVERE AIRFRAME ICING.

Narrative: WAS ASSIGNED TO CROSS FLAAK INTXN AT 11000 FT AND THEN DSND DOWN TO 10000 FT. WAS NOT ABLE TO MAINTAIN ASSIGNED 10000 FT DUE TO SEVERE ACFT STRUCTURAL ICING.

Data retrieved from NASA's ASRS site as of May 2009 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.