Flight and Weather Briefing
The pilot received a preflight weather briefing that included advisories for icing conditions, scattered thunderstorms, and moderate to severe turbulence. The briefer indicated that radar showed a large area of echoes over the route of flight with light to moderate intensities, cloud tops up to 24,000 feet, and a high likelihood of icing conditions between 15,000 and 24,000 feet. The airplane was equipped with a Stormscope but not weather radar.
Flight Progression
The pilot filed an IFR flight plan with a cruising altitude of 17,000 feet. After takeoff and reaching 17,000 feet, the pilot requested and received clearance to climb to 19,000 feet. Within the next three minutes, the pilot requested a deviation to the left and then a further climb to 21,000 feet, both of which were approved.
Loss of Communication
Shortly thereafter, the pilot advised the controller that he had "really went through some bad turbulence here." The controller inquired about the pilot's heading and altitude. The pilot responded that he wanted to climb back to altitude but was still in instrument meteorological conditions (IMC). This was the last communication from the flight.
According to the controller's recollection of the radar display, the airplane had deviated north, made a U-turn, descended to 19,000 feet, and was beginning to return to course when it disappeared from radar. The controller provided no weather deviations or support after the flight encountered weather, lost altitude, and reported significant turbulence. A limited overlay of weather echoes was available to the controller.
Weather Conditions
Weather data indicated a shear level at 19,800 feet with an 11.1-knot change in wind speed per 1,000 feet, which had a high probability of severe turbulence. The data also showed a 92 percent probability of rime icing at 20,000 feet. The pilot's requests to climb to higher altitudes were likely made in an attempt to exit icing conditions and climb over towering cumulus cloud tops.
The airplane departed controlled flight after encountering the forecast conditions and collided with the ground in a near-vertical spinning descent.