Bonanza 36
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Sea
Flight Crew Last 90 Days 90; Flight Crew Total 12000; Flight Crew Type 11500
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Aircraft; Weather
I was flying on an IFR flight plan at assigned altitude of 4000'. After seeing a cell on FIS-B radar (Flight Information System-Broadcast); I requested from ATC if there were any PIREPS for the weather. I then requested a deviation for weather depicted by FIS-B. I was granted the requested weather deviation and was flying outside of the weather depicted by FIS-B several miles in IMC conditions. Apparently; I flew into an embedded thunderstorm cell with both severe turbulence and violent downdrafts and updrafts which was not depicted by FIS-B weather with a 4 minute time stamp.I noticed the IAS had climbed dangerously high into the yellow arc while on autopilot (AP) maintaining an altitude of 4;000'. I reduced power to idle in an effort to maintain a safe indicated airspeed. While the AP was engaged and power reduced the IAS did not reduce sufficiently to the maneuvering speed but was rapidly climbing. I disconnected the AP and pulled the yoke back to reduce IAS. I then encountered severe turbulence and downdrafts forcing the aircraft to lose approximately 500 feet. In an attempt to stabilize the aircraft; I attempted to various throttle settings in an attempt to maintain altitude and heading with little success in controlling altitude or heading.The entire event lasted approximately 2 minutes with several calls from ATC offering assistance. During those calls I requested ATC standby until I was able to regain control of the aircraftThis was an isolated cell whose location was not accurately depicted by FIS-B weather radar returns. In regards to corrective actions on my part as pilot; I'd say to not trust FIS-B time stamps nor the weather depictions as being reasonably accurate. Further I'd extend my safety margin around weather depicted on FIS-B to a greater margin.The flight terminated without incident with my cancelling my IFR flight plan once out of IMC conditions and safely landing at the destination airport.
BE36 pilot reported difficulty controlling altitude and heading after entering a thunderstorm that was not depicted on Flight Information System-Broadcast (FIS-B).