Aircraft Accident/Incident Report

Grand Canyon, Arizona 86023
Sunday, September 8, 2002 11:35 MST

The airplane departed from controlled flight after encountering forecast conditions including moderate turbulence and icing during a cross-country instrument flight and collided with the ground in a near vertical spinning descent. The airplane was equipped with a Stormscope, but not weather radar. The pilot received a preflight weather briefing that included advisories for icing conditions, scattered thunderstorms, and moderate to severe turbulence. The briefer advised that radar indicated a large area of echoes extended over the route of flight with light to moderate intensities and that cloud tops were up to 24,000 feet with scattered thunderstorms and a high likelihood of icing conditions between 15,000 and 24,000 feet. The pilot filed his IFR flight plan with a cruising altitude of 17,000 feet. After takeoff and achieving 17,000 feet, the pilot asked the center controller for a clearance to a higher altitude of 19,000 feet, which was approved. Within the next 3 minutes the pilot made a request to deviate to the left and then to climb higher to 21,000 feet, which were all approved. Shortly thereafter, the pilot advised he "really went through some bad turbulence here," and the controller inquired about his heading and altitude. The pilot advised he wanted to climb back to altitude but he was still in IMC conditions. That was the last communication from the flight. According to the controller's memory of the radar display, the airplane was getting into some weather and had deviated north, made a u-turn and had gone down to 19,000 feet, and had started getting back on course when it disappeared. The requests from the pilot to climb to higher altitude was likely made to climb out of icing conditions and an attempt to climb over some of the towering cumulus clouds tops. A limited overlay of weather echoes that would have been available to the controller. The controller provided no weather deviations or support even after the flight encountered some weather, lost altitude, and reported encountering significant turbulence. The weather data showed a shear level was at 19,800 feet, with a 11.1 knot per 1,000 feet change in wind speed. This shear layer 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 inadequate in-flight planning/decision and his failure to maintain adequate airspeed which resulted in an encounter with adverse weather conditions and the loss of control due to a stall. Contributing factors were thunderstorm related turbulence, icing conditions, the pilot's disregard of the weather forecast.