Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 25; Flight Crew Total 3500; Flight Crew Type 2000
Communication Breakdown
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Regained Aircraft Control
Weather
While deviating through a break (approx 15 miles wide) between two ends of a long line of thunderstorms cells from W Maryland northeasterly through Western PA in IMC conditions; I encountered approx 2 mins of moderate to severe turbulence. Initially there was an uncontrolled climb from 9000 ft to 9400 ft; then down to about 8800 ft; then up to about 9500 ft; all before I could inform Cleveland Center of my problem.He informed me of 9400 foot deviation; thinking it was an error on his equipment to which I informed him; it was not. There had been no warning; thus no time to inform the controller beforehand of the extreme vertical air currents I was encountering. He said there were no other aircraft near and I could deviate vertically as needed. About 5 minutes previously; I had intermittent ground contact and requested lower; which wasn't approved. I was switched to Harrisburg Approach four times but couldn't even get to the mike switch because of the severe turbulence. Upon contacting Harrisburg Approach; I again requested lower which was approved. After about 2 minutes; I broke into the sct/clear skies again. Rest of trip uneventful.
Part 91 aircraft encountered moderate to severe turbulence while deviating around weather.