Narrative:

The first flight of the day was from cottage grove, or (61S) to crescent city, ca (cec). A (second) complete briefing at the cec FSS suggested that the severe icing was between 10000 and 20000 ft MSL based on pilot reports. Only 7000 ft was required for the MEA to go from crescent city to san luis obispo. The first leg of the flight was uneventful (to fortuna VOR), but south of fortuna, better WX was visible west of the airway, and permission from ZSE to deviate west was obtained. Shortly thereafter, however, seattle ATC requested we rejoin the airway or climb to 10000 ft. There was no ice visible anywhere on the airplane at that time. I chose to climb to stay in the clrer area, and was handed off to ZOA soon thereafter. I began to pick up a little bit of ice and told center I would return to the airway. Within about 2 mins, a huge amount of ice accumulated on the wings: 2-3 inches in thickness (uneven) and extending back from the leading edges 12-18 inches along the entire length of the wings. I noted my position as 45 NM north of the ukiah VOR and my ground speed readout was about 69 KTS. Normal airspeed is 130-135 KTS at cruise setting. There was a 30- 40 KT headwind. I assumed about 30 KT loss of speed due to the large accumulation of ice. To maintain my airspeed, I was descending at 300-500 FPM. I immediately notified ATC of this situation. They informed me that the MEA was 6100 ft in my area. I concluded that I would be unable to safely reach ukiah, and that immediate corrective action was necessary. I asked ATC for a heading to the nearest town along the coastline. I also asked for the highest peaks from my position along that heading. Given that there was a peak of 4500 ft, I chose to turn more sharply (about 220 degrees) to avoid high terrain. I was able to sight ocean below at 5500 ft, and was able to descend through an opening in the clouds to about 1500 where most of the ice broke loose from the airplane. I was able to land at the little river airport (O48) which is about 12 mi south of ft bragg without any further difficulties. What really caused the problem? Of course, entering known icing conditions caused the problem, but the situation is much more complex than that. IFR flts into known icing conditions are made by many pilots every day. Several factors led to my decisions for the flight in question. 1) I had just made a successful flight through what I assumed to be the same or similar conditions as those I was about to enter. 2) I assumed that as I moved sward, the icing severity would lessen. 3) I had never flown in severe icing conditions, and did not really believe that so much ice could accumulate so quickly. 4) at the FSS in crescent city, my flight plan appeared reasonable to me, and I believe, to the briefer, with whom I met for 20-30 mins prior to departure. Due to the rapid accumulation of ice, turning around did not seem to be a viable choice. Descending below the freezing level over water or flat terrain appeared to me to be the only reasonable course of action. Despite the errors in judgement I may have made (as outlined above), there were several things I did well which might be helpful to pilots in the future. 1) I had a preplanned escape route in case a severe icing encounter did take place, and I was, in fact, able to execute the escape route essentially as planned. Once I realized that I could not continue with my flight plan, I knew exactly what I would do and went about doing it. 2) I had in fact checked at the FSS in crescent city, and I knew the freezing level to be between 4000 and 7000 ft MSL. My own instrument indicated 4000 ft, so I knew that I could shed the ice providing I could safely descend below that level. I also was aware from that briefing that cloud bottoms ranged between 500 and 2000 ft. Thus, I undertook a flight that I believed I had a good escape route from if needed. I do not believe I would have undertaken any flts that day, had the freezing level been at the ground level or if there was fog along much of the coastline. I think these are extremely important factors for pilots to evaluate before initiating an IFR flight. 3)one other thing that I learned that day was that as PIC, I could, and did, choose to immediately follow my emergency escape plan, and to use ATC for help as I might have used a crew member in establishing nearest airports, highest terrain, etc. Had I continued to comply with ATC requests (for altitude and destination), I believe I could not have concluded the flight successfully. I think it is very important for pilots to understand that rapid action in such a situation can make all the difference between disaster and safe landing. 4) I also learned later on (i.e., on the ground) talking to ZOA that I probably could have continued at 7000 ft along the more westerly route I preferred. There is good radio communication along that route, but no radar following. Because the seattle air traffic controller told me I could not continue at 7000 ft, I never thought to ask oakland ATC the same question. I believe they would have allowed me to do this, and there is a fairly good likelihood that there was no severe icing at that altitude as prior pilot reports had indicated.

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Original NASA ASRS Text

Title: SMA ENCOUNTERS RAPID ICE BUILDUP. UNABLE TO MAINTAIN ALT. DSNDS TO VFR, LANDS.

Narrative: THE FIRST FLT OF THE DAY WAS FROM COTTAGE GROVE, OR (61S) TO CRESCENT CITY, CA (CEC). A (SECOND) COMPLETE BRIEFING AT THE CEC FSS SUGGESTED THAT THE SEVERE ICING WAS BTWN 10000 AND 20000 FT MSL BASED ON PLT RPTS. ONLY 7000 FT WAS REQUIRED FOR THE MEA TO GO FROM CRESCENT CITY TO SAN LUIS OBISPO. THE FIRST LEG OF THE FLT WAS UNEVENTFUL (TO FORTUNA VOR), BUT S OF FORTUNA, BETTER WX WAS VISIBLE W OF THE AIRWAY, AND PERMISSION FROM ZSE TO DEVIATE W WAS OBTAINED. SHORTLY THEREAFTER, HOWEVER, SEATTLE ATC REQUESTED WE REJOIN THE AIRWAY OR CLB TO 10000 FT. THERE WAS NO ICE VISIBLE ANYWHERE ON THE AIRPLANE AT THAT TIME. I CHOSE TO CLB TO STAY IN THE CLRER AREA, AND WAS HANDED OFF TO ZOA SOON THEREAFTER. I BEGAN TO PICK UP A LITTLE BIT OF ICE AND TOLD CTR I WOULD RETURN TO THE AIRWAY. WITHIN ABOUT 2 MINS, A HUGE AMOUNT OF ICE ACCUMULATED ON THE WINGS: 2-3 INCHES IN THICKNESS (UNEVEN) AND EXTENDING BACK FROM THE LEADING EDGES 12-18 INCHES ALONG THE ENTIRE LENGTH OF THE WINGS. I NOTED MY POS AS 45 NM N OF THE UKIAH VOR AND MY GND SPD READOUT WAS ABOUT 69 KTS. NORMAL AIRSPD IS 130-135 KTS AT CRUISE SETTING. THERE WAS A 30- 40 KT HEADWIND. I ASSUMED ABOUT 30 KT LOSS OF SPD DUE TO THE LARGE ACCUMULATION OF ICE. TO MAINTAIN MY AIRSPD, I WAS DSNDING AT 300-500 FPM. I IMMEDIATELY NOTIFIED ATC OF THIS SIT. THEY INFORMED ME THAT THE MEA WAS 6100 FT IN MY AREA. I CONCLUDED THAT I WOULD BE UNABLE TO SAFELY REACH UKIAH, AND THAT IMMEDIATE CORRECTIVE ACTION WAS NECESSARY. I ASKED ATC FOR A HDG TO THE NEAREST TOWN ALONG THE COASTLINE. I ALSO ASKED FOR THE HIGHEST PEAKS FROM MY POS ALONG THAT HDG. GIVEN THAT THERE WAS A PEAK OF 4500 FT, I CHOSE TO TURN MORE SHARPLY (ABOUT 220 DEGS) TO AVOID HIGH TERRAIN. I WAS ABLE TO SIGHT OCEAN BELOW AT 5500 FT, AND WAS ABLE TO DSND THROUGH AN OPENING IN THE CLOUDS TO ABOUT 1500 WHERE MOST OF THE ICE BROKE LOOSE FROM THE AIRPLANE. I WAS ABLE TO LAND AT THE LITTLE RIVER ARPT (O48) WHICH IS ABOUT 12 MI S OF FT BRAGG WITHOUT ANY FURTHER DIFFICULTIES. WHAT REALLY CAUSED THE PROB? OF COURSE, ENTERING KNOWN ICING CONDITIONS CAUSED THE PROB, BUT THE SIT IS MUCH MORE COMPLEX THAN THAT. IFR FLTS INTO KNOWN ICING CONDITIONS ARE MADE BY MANY PLTS EVERY DAY. SEVERAL FACTORS LED TO MY DECISIONS FOR THE FLT IN QUESTION. 1) I HAD JUST MADE A SUCCESSFUL FLT THROUGH WHAT I ASSUMED TO BE THE SAME OR SIMILAR CONDITIONS AS THOSE I WAS ABOUT TO ENTER. 2) I ASSUMED THAT AS I MOVED SWARD, THE ICING SEVERITY WOULD LESSEN. 3) I HAD NEVER FLOWN IN SEVERE ICING CONDITIONS, AND DID NOT REALLY BELIEVE THAT SO MUCH ICE COULD ACCUMULATE SO QUICKLY. 4) AT THE FSS IN CRESCENT CITY, MY FLT PLAN APPEARED REASONABLE TO ME, AND I BELIEVE, TO THE BRIEFER, WITH WHOM I MET FOR 20-30 MINS PRIOR TO DEP. DUE TO THE RAPID ACCUMULATION OF ICE, TURNING AROUND DID NOT SEEM TO BE A VIABLE CHOICE. DSNDING BELOW THE FREEZING LEVEL OVER WATER OR FLAT TERRAIN APPEARED TO ME TO BE THE ONLY REASONABLE COURSE OF ACTION. DESPITE THE ERRORS IN JUDGEMENT I MAY HAVE MADE (AS OUTLINED ABOVE), THERE WERE SEVERAL THINGS I DID WELL WHICH MIGHT BE HELPFUL TO PLTS IN THE FUTURE. 1) I HAD A PREPLANNED ESCAPE RTE IN CASE A SEVERE ICING ENCOUNTER DID TAKE PLACE, AND I WAS, IN FACT, ABLE TO EXECUTE THE ESCAPE RTE ESSENTIALLY AS PLANNED. ONCE I REALIZED THAT I COULD NOT CONTINUE WITH MY FLT PLAN, I KNEW EXACTLY WHAT I WOULD DO AND WENT ABOUT DOING IT. 2) I HAD IN FACT CHKED AT THE FSS IN CRESCENT CITY, AND I KNEW THE FREEZING LEVEL TO BE BTWN 4000 AND 7000 FT MSL. MY OWN INST INDICATED 4000 FT, SO I KNEW THAT I COULD SHED THE ICE PROVIDING I COULD SAFELY DSND BELOW THAT LEVEL. I ALSO WAS AWARE FROM THAT BRIEFING THAT CLOUD BOTTOMS RANGED BTWN 500 AND 2000 FT. THUS, I UNDERTOOK A FLT THAT I BELIEVED I HAD A GOOD ESCAPE RTE FROM IF NEEDED. I DO NOT BELIEVE I WOULD HAVE UNDERTAKEN ANY FLTS THAT DAY, HAD THE FREEZING LEVEL BEEN AT THE GND LEVEL OR IF THERE WAS FOG ALONG MUCH OF THE COASTLINE. I THINK THESE ARE EXTREMELY IMPORTANT FACTORS FOR PLTS TO EVALUATE BEFORE INITIATING AN IFR FLT. 3)ONE OTHER THING THAT I LEARNED THAT DAY WAS THAT AS PIC, I COULD, AND DID, CHOOSE TO IMMEDIATELY FOLLOW MY EMER ESCAPE PLAN, AND TO USE ATC FOR HELP AS I MIGHT HAVE USED A CREW MEMBER IN ESTABLISHING NEAREST ARPTS, HIGHEST TERRAIN, ETC. HAD I CONTINUED TO COMPLY WITH ATC REQUESTS (FOR ALT AND DEST), I BELIEVE I COULD NOT HAVE CONCLUDED THE FLT SUCCESSFULLY. I THINK IT IS VERY IMPORTANT FOR PLTS TO UNDERSTAND THAT RAPID ACTION IN SUCH A SIT CAN MAKE ALL THE DIFFERENCE BTWN DISASTER AND SAFE LNDG. 4) I ALSO LEARNED LATER ON (I.E., ON THE GND) TALKING TO ZOA THAT I PROBABLY COULD HAVE CONTINUED AT 7000 FT ALONG THE MORE WESTERLY RTE I PREFERRED. THERE IS GOOD RADIO COM ALONG THAT RTE, BUT NO RADAR FOLLOWING. BECAUSE THE SEATTLE AIR TFC CTLR TOLD ME I COULD NOT CONTINUE AT 7000 FT, I NEVER THOUGHT TO ASK OAKLAND ATC THE SAME QUESTION. I BELIEVE THEY WOULD HAVE ALLOWED ME TO DO THIS, AND THERE IS A FAIRLY GOOD LIKELIHOOD THAT THERE WAS NO SEVERE ICING AT THAT ALT AS PRIOR PLT RPTS HAD INDICATED.

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.