Weather Briefing and Flight
The pilot received a full weather briefing at 0540 CDT and an update at 0737 when filing an IFR flight plan. The flight proceeded without incident at a final cruise altitude of 16,000 feet.
Loss of Control
At 1055:43, the pilot requested a "left turn for deviation." About three minutes later, the controller noted an altitude alert when the aircraft deviated below its assigned altitude. Attempts to contact the pilot were unsuccessful, and both radio and radar contact were lost.
Witness Observations
Shortly after, witnesses saw the aircraft come out of clouds in a steep right-wing-low, nose-down attitude. It crashed with a high rate of speed and disintegrated on impact, with parts of the wreckage entering a nearby lake.
Investigation Findings
No pre-impact part failure or malfunction was found. Weather radar indicated a line of thunderstorms moving through the area at 35 knots, with tops reaching 34,000 feet. The 1102 Austin weather observation reported thunderstorms with wind from 010 degrees at 18 knots, gusting to 32 knots.
Weather Briefing Details
The pilot received a detailed thunderstorm briefing at 0540, but the update briefing at 0737 did not include pertinent information from Severe Thunderstorm Watch #516 (issued at 0611) or Convective SIGMET 18C. The pilot did not request an update of the weather he was approaching. The aircraft was equipped with radar.