This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
I was cruising at 8,000 feet in a Bonanza 36 on an IFR flight when I entered a benign cloud bank.
Shortly after going IMC, I encountered localized extreme turbulence, hitting my head on the ceiling, and the autopilot disconnected. I was stunned momentarily, but then realized the plane was in an unusual attitude (i.e. dive) and with very strong downdrafts and heavy controls.
I recovered from the unusual attitude and I informed ATC that I had encountered extreme turbulence and downdrafts and could not hold altitude.
Exiting IMC, the turbulence subsided and I had lost several thousand feet of altitude.
I requested and was cleared to 6,000 and completed the flight without further incident.
I think that the extremely high temperatures (near 100°) on the ground and flying in the afternoon heat cumulatively contributed to a localized turbulent weather condition.
The weather picture on the avionics did not show either precipitation, lightning, nor storm cell attributes at my position (or projected path), however there was evidently enough energy in the air to cause the extreme localized turbulence and downdrafts encountered.
Primary Problem: Weather
ACN: 2140217
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