FTW83LA425

Before takeoff, the plt was briefed on the wx, including SIGMET 20C, which called for imbedded thunderstorms. While en route, he deviated around an area of wx & was provided vectors to avoid storm cells. In the vicinity of Daisetta, TX, the controller suggested a further deviation to the north due to wx. The plt responded that a north turn would take him into a cb type cloud. He declined the turn & continued on his heading. About 10 mi later, while cruising at 8000 ft, he encountered heavy rain & a violent downdraft & lost more than 3500 ft in a short time. During the encounter, the eng cowling separated & knocked out the windshield. The primary flt instruments became inop & extensive deformation of the airframe was sustained. The plt subsequently recovered in VFR conditions below the clouds &made an emergency landing at cleveland, TX.