Small aircraft pilot on IFR flight encounters unforecast severe icing and begins uncontrolled descen...

Attributes
ACN	203141
Time
Date	199203
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : eni
State Reference	CA
Altitude	msl bound lower : 6300 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Route In Use	enroute airway : zoa
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 75 flight time total : 1400 flight time type : 900
ASRS Report	203141
Person 2
Function	flight crew : single pilot
Qualification	pilot : private
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter : weather other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : regained aircraft control flight crew : declared emergency other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Weather

Narrative:

Entered a cloud layer at 8000 ft. Air temperature was plus 1 degree C. First few mins, encountered rain. This immediately turned to ice-moderate to severe mixed ice. Lost 200 ft. Told ATC of problem. Asked for lower as an small aircraft can't climb. Was denied due to plane overtaking me at 7000 ft. (Radar service was not working at this time). Immediately, my plane went into a rapid descent and airspeed started decreasing. Checked to see if pitot heat was on. It was. Now, I'm telling center, I'm in a rapid descent. They asked my altitude. I told them 6500 ft (note: I informed center twice that I could not hold altitude). They told me to make an immediate right turn. I complied. I then broke into VMC at 6300 ft with a 20 mi visibility below. I then landed at ukiah, and, at ATC request, called them on the phone to give them an explanation of what happened. The problem, as I described, happened over a period of 30 seconds. I have over 150 hours of actual IFR. But have never encountered so much ice so fast. The forecast was for scattered to broken all along the route with no forecast or PIREPS of icing at that altitude. In analyzing this, I feel that I acted in the correct manner and continuously kept ATC advised of the situation. The landing at ukiah was my decision as a precautionary measure. I was en route from concord to eureka. I felt once on the ground I could check on my equipment. Check on WX and give a PIREP to FSS.

Original NASA ASRS Text

Title: SMA PLT ON IFR FLT ENCOUNTERS UNFORECAST SEVERE ICING AND BEGINS UNCTLED DSCNT ON TOP OF OTHER IFR IMC TFC. ARTCC CTLR APPARENTLY DOES NOT HAVE RADAR AND ISSUES A TURN TO THE RPTR FOR CONFLICT AVOIDANCE.

Narrative: ENTERED A CLOUD LAYER AT 8000 FT. AIR TEMP WAS PLUS 1 DEG C. FIRST FEW MINS, ENCOUNTERED RAIN. THIS IMMEDIATELY TURNED TO ICE-MODERATE TO SEVERE MIXED ICE. LOST 200 FT. TOLD ATC OF PROBLEM. ASKED FOR LOWER AS AN SMA CAN'T CLB. WAS DENIED DUE TO PLANE OVERTAKING ME AT 7000 FT. (RADAR SVC WAS NOT WORKING AT THIS TIME). IMMEDIATELY, MY PLANE WENT INTO A RAPID DSCNT AND AIRSPD STARTED DECREASING. CHKED TO SEE IF PITOT HEAT WAS ON. IT WAS. NOW, I'M TELLING CTR, I'M IN A RAPID DSCNT. THEY ASKED MY ALT. I TOLD THEM 6500 FT (NOTE: I INFORMED CTR TWICE THAT I COULD NOT HOLD ALT). THEY TOLD ME TO MAKE AN IMMEDIATE R TURN. I COMPLIED. I THEN BROKE INTO VMC AT 6300 FT WITH A 20 MI VISIBILITY BELOW. I THEN LANDED AT UKIAH, AND, AT ATC REQUEST, CALLED THEM ON THE PHONE TO GIVE THEM AN EXPLANATION OF WHAT HAPPENED. THE PROBLEM, AS I DESCRIBED, HAPPENED OVER A PERIOD OF 30 SECS. I HAVE OVER 150 HRS OF ACTUAL IFR. BUT HAVE NEVER ENCOUNTERED SO MUCH ICE SO FAST. THE FORECAST WAS FOR SCATTERED TO BROKEN ALL ALONG THE RTE WITH NO FORECAST OR PIREPS OF ICING AT THAT ALT. IN ANALYZING THIS, I FEEL THAT I ACTED IN THE CORRECT MANNER AND CONTINUOUSLY KEPT ATC ADVISED OF THE SITUATION. THE LNDG AT UKIAH WAS MY DECISION AS A PRECAUTIONARY MEASURE. I WAS ENRTE FROM CONCORD TO EUREKA. I FELT ONCE ON THE GND I COULD CHK ON MY EQUIP. CHK ON WX AND GIVE A PIREP TO FSS.

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.

Small aircraft pilot on IFR flight encounters unforecast severe icing and begins uncontrolled descent on top of other IFR IMC traffic. ARTCC controller apparently does not have radar and issues a turn to the reporter for conflict avoidance.