Narrative:

I was flying in VMC conditions; but with clouds and IMC conditions in the area; at 13000 ft MSL on an IFR flight plan. I was issued a descent from 13000 ft to 12000 ft and was beginning that descent. Shortly into the descent; I noticed that my airspeed was increasing dramatically; and instead of descending I was climbing. Normal descent speeds at this altitude are about 160-165 KIAS (just at the bottom of the yellow); with a descent rate of 500 FPM. The airplane was flying on autoplt at the time. But in this case I noticed that the airspeed had significantly exceeded this and was climbing towards 200 KIAS (red line on this airplane is 204 KIAS) and was still not descending; and in fact I had climbed to at least 13500 ft by then; and was about to enter a cloud. This set off all my personal alarm bells as I expected that shortly after penetrating the cloud I would hit turbulence; and with this updraft I expected violent turbulence; and I was well above the structural maneuver speed. I immediately disengaged the autoplt; reduce power to idle; and slowly pulled the nose up to bleed off airspeed. Then I penetrated the cloud; and almost immediately hit the turbulence; and thankfully by then the airspeed was down to around 150 KTS; still above the maneuver speed; (maneuver speed at our weight was about 135 KIAS) but not near the red line as it was before. The turbulence was more an impact than turbulence; and everything in the airplane was flying around the cabin. This was the worst turbulence I had ever experienced in over 33 yrs of flying. (I would classify it as extreme; I do not think that the term severe is adequate to describe what we were in.) by now with engines at idle; and speed at about 140 KIAS; we were climbing with the vsi pegged at 2000 FPM; and were climbing through 14500 ft; then we hit the downdraft; and again it was more of an impact than turbulence. I added full power; and established 110 KIAS (the normal climb speed) and by this time we were descending with the vsi pegged in a descent over 2000 FPM; and soon we were descending through 10000 ft. This updraft/downdraft cycle went on for about 2-3 iterations. The next issue was ice. I didn't have much time to look at the wings; but there was by now nearly 3/4 inch of mixed ice on the wing leading edges. (We had only been in this cloud for 2-5 mins at the most.) then we exited the cloud; and now we were in what I would describe as severe turbulence for the next 10 mins. During all this time I tried to contact either ZSE; or great falls approach (I cannot remember which; as it was at this time that I was switched) on the radio to advise them of my altdevs; I was not able to get a reply; until I left the cloud; and was now in the calmer severe turbulence. I advised them of the altdevs; the extreme turbulence; and the severe icing encounter; and made sure that they were aware not to send anyone near that area.

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Original NASA ASRS Text

Title: PA34 PILOT ENCOUNTERS SEVERE TO EXTREME TURBULENCE AND SEVERE ICING WHILE TRANSITING A LARGE CLOUD ON AN IFR FLIGHT.

Narrative: I WAS FLYING IN VMC CONDITIONS; BUT WITH CLOUDS AND IMC CONDITIONS IN THE AREA; AT 13000 FT MSL ON AN IFR FLT PLAN. I WAS ISSUED A DSCNT FROM 13000 FT TO 12000 FT AND WAS BEGINNING THAT DSCNT. SHORTLY INTO THE DSCNT; I NOTICED THAT MY AIRSPD WAS INCREASING DRAMATICALLY; AND INSTEAD OF DSNDING I WAS CLBING. NORMAL DSCNT SPDS AT THIS ALT ARE ABOUT 160-165 KIAS (JUST AT THE BOTTOM OF THE YELLOW); WITH A DSCNT RATE OF 500 FPM. THE AIRPLANE WAS FLYING ON AUTOPLT AT THE TIME. BUT IN THIS CASE I NOTICED THAT THE AIRSPD HAD SIGNIFICANTLY EXCEEDED THIS AND WAS CLBING TOWARDS 200 KIAS (RED LINE ON THIS AIRPLANE IS 204 KIAS) AND WAS STILL NOT DSNDING; AND IN FACT I HAD CLBED TO AT LEAST 13500 FT BY THEN; AND WAS ABOUT TO ENTER A CLOUD. THIS SET OFF ALL MY PERSONAL ALARM BELLS AS I EXPECTED THAT SHORTLY AFTER PENETRATING THE CLOUD I WOULD HIT TURB; AND WITH THIS UPDRAFT I EXPECTED VIOLENT TURB; AND I WAS WELL ABOVE THE STRUCTURAL MANEUVER SPD. I IMMEDIATELY DISENGAGED THE AUTOPLT; REDUCE PWR TO IDLE; AND SLOWLY PULLED THE NOSE UP TO BLEED OFF AIRSPD. THEN I PENETRATED THE CLOUD; AND ALMOST IMMEDIATELY HIT THE TURB; AND THANKFULLY BY THEN THE AIRSPD WAS DOWN TO AROUND 150 KTS; STILL ABOVE THE MANEUVER SPD; (MANEUVER SPD AT OUR WT WAS ABOUT 135 KIAS) BUT NOT NEAR THE RED LINE AS IT WAS BEFORE. THE TURB WAS MORE AN IMPACT THAN TURB; AND EVERYTHING IN THE AIRPLANE WAS FLYING AROUND THE CABIN. THIS WAS THE WORST TURB I HAD EVER EXPERIENCED IN OVER 33 YRS OF FLYING. (I WOULD CLASSIFY IT AS EXTREME; I DO NOT THINK THAT THE TERM SEVERE IS ADEQUATE TO DESCRIBE WHAT WE WERE IN.) BY NOW WITH ENGS AT IDLE; AND SPD AT ABOUT 140 KIAS; WE WERE CLBING WITH THE VSI PEGGED AT 2000 FPM; AND WERE CLBING THROUGH 14500 FT; THEN WE HIT THE DOWNDRAFT; AND AGAIN IT WAS MORE OF AN IMPACT THAN TURB. I ADDED FULL PWR; AND ESTABLISHED 110 KIAS (THE NORMAL CLB SPD) AND BY THIS TIME WE WERE DSNDING WITH THE VSI PEGGED IN A DSCNT OVER 2000 FPM; AND SOON WE WERE DSNDING THROUGH 10000 FT. THIS UPDRAFT/DOWNDRAFT CYCLE WENT ON FOR ABOUT 2-3 ITERATIONS. THE NEXT ISSUE WAS ICE. I DIDN'T HAVE MUCH TIME TO LOOK AT THE WINGS; BUT THERE WAS BY NOW NEARLY 3/4 INCH OF MIXED ICE ON THE WING LEADING EDGES. (WE HAD ONLY BEEN IN THIS CLOUD FOR 2-5 MINS AT THE MOST.) THEN WE EXITED THE CLOUD; AND NOW WE WERE IN WHAT I WOULD DESCRIBE AS SEVERE TURB FOR THE NEXT 10 MINS. DURING ALL THIS TIME I TRIED TO CONTACT EITHER ZSE; OR GREAT FALLS APCH (I CANNOT REMEMBER WHICH; AS IT WAS AT THIS TIME THAT I WAS SWITCHED) ON THE RADIO TO ADVISE THEM OF MY ALTDEVS; I WAS NOT ABLE TO GET A REPLY; UNTIL I LEFT THE CLOUD; AND WAS NOW IN THE CALMER SEVERE TURB. I ADVISED THEM OF THE ALTDEVS; THE EXTREME TURB; AND THE SEVERE ICING ENCOUNTER; AND MADE SURE THAT THEY WERE AWARE NOT TO SEND ANYONE NEAR THAT AREA.

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.