Narrative:

The line was apparently intensifying because everyone from cherokees to commuters were deviating and reporting moderate to occasional severe turbulence. I had encountered only occasional moderate turbulence. I could not rely on the WX radar because, with the almost constant changes in pitch attitude, the radar had a tendency to paint ground clutter. I had throttled back to a power setting I knew would yield an airspeed that was less than the placarded maneuvering speed just in case I hit a nasty bump. All of a sudden, wham! Everything that wasn't tied down in the cockpit and cabin went airborne. The airplane was completely out of my control. I managed to declare an emergency. The whole cabin had filled with a white, smoky looking substance. I assumed it may have been some sort of smoke, even though it had no odor. So when dayton approach responded to my emergency call I told them I wished to descend. I was cleared to 3000 ft MSL. By the time I reached 3000 ft MSL, I was out of the clouds and able to see the churning, black mass of clouds I had just been in. There was no fire. The white cloud came from the fire extinguisher itself. The portable fire extinguisher was tossed about and discharged causing the cloud. I consider myself lucky to be alive. I returned to 3i7 and called it a day. Not 30 mins after I landed, severe thunderstorm warnings were issued for my area, and a tornado touchdown was reported not 15 mi from 3i7.

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Original NASA ASRS Text

Title: A PVT SMA TWIN PLT HAD TO RETURN LAND DUE TO SEVERE TURB.

Narrative: THE LINE WAS APPARENTLY INTENSIFYING BECAUSE EVERYONE FROM CHEROKEES TO COMMUTERS WERE DEVIATING AND RPTING MODERATE TO OCCASIONAL SEVERE TURB. I HAD ENCOUNTERED ONLY OCCASIONAL MODERATE TURB. I COULD NOT RELY ON THE WX RADAR BECAUSE, WITH THE ALMOST CONSTANT CHANGES IN PITCH ATTITUDE, THE RADAR HAD A TENDENCY TO PAINT GND CLUTTER. I HAD THROTTLED BACK TO A PWR SETTING I KNEW WOULD YIELD AN AIRSPD THAT WAS LESS THAN THE PLACARDED MANEUVERING SPD JUST IN CASE I HIT A NASTY BUMP. ALL OF A SUDDEN, WHAM! EVERYTHING THAT WASN'T TIED DOWN IN THE COCKPIT AND CABIN WENT AIRBORNE. THE AIRPLANE WAS COMPLETELY OUT OF MY CTL. I MANAGED TO DECLARE AN EMER. THE WHOLE CABIN HAD FILLED WITH A WHITE, SMOKY LOOKING SUBSTANCE. I ASSUMED IT MAY HAVE BEEN SOME SORT OF SMOKE, EVEN THOUGH IT HAD NO ODOR. SO WHEN DAYTON APCH RESPONDED TO MY EMER CALL I TOLD THEM I WISHED TO DSND. I WAS CLRED TO 3000 FT MSL. BY THE TIME I REACHED 3000 FT MSL, I WAS OUT OF THE CLOUDS AND ABLE TO SEE THE CHURNING, BLACK MASS OF CLOUDS I HAD JUST BEEN IN. THERE WAS NO FIRE. THE WHITE CLOUD CAME FROM THE FIRE EXTINGUISHER ITSELF. THE PORTABLE FIRE EXTINGUISHER WAS TOSSED ABOUT AND DISCHARGED CAUSING THE CLOUD. I CONSIDER MYSELF LUCKY TO BE ALIVE. I RETURNED TO 3I7 AND CALLED IT A DAY. NOT 30 MINS AFTER I LANDED, SEVERE TSTM WARNINGS WERE ISSUED FOR MY AREA, AND A TORNADO TOUCHDOWN WAS RPTED NOT 15 MI FROM 3I7.

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.