The airplane flew into an area of severe thunderstorms identified as a mesoscale convective system (or "MCS") with intense to extreme intensities during cruise flight at 11,000 feet then descended rapidly and impacted the terrain. The on-scene investigation revealed no preimpact mechanical malfunctions or anomalies that would have prevented the normal operation of the airplane or its systems.

The airplane entered the severe convective weather; the pilot then requested and received clearance from the air traffic controller to initiate a turn to escape the weather. The airplane was lost from radar about 30 seconds after the pilot initiated the turn. Before the airplane entered the weather, the controller's radar scope depicted a band of moderate to extreme weather along the accident airplane's projected flightpath that was consistent with an embedded, heavy-precipitation, supercell-type thunderstorm; however, the controller did not provide the pilot with any severe weather advisories and did not advise the pilot of the weather depicted on his radar scope.

Although Federal Aviation Administration directives state that controllers should give first priority to separating aircraft and issuing safety alerts, the directives further state that controllers should use good judgment and first perform the action that is most critical from a safety standpoint. Review of air traffic communications and radar data identified no air traffic control (ATC) radar limitations, no excessive traffic, no radio frequency congestion, and no controller workload issues that would have prevented the controller from issuing pertinent weather information to the accident pilot. On the basis of the controller's workload and available resources, he should have recognized that the adverse weather represented an immediate safety hazard to the accident flight and should have provided appropriate advisories to the pilot.

The pilot obtained several weather briefings before departure. At that time, the current weather along the route of flight showed significant convective activity and a moving squall line, and the forecast predicted significant thunderstorm activity along the planned route of flight. The pilot also discussed the weather with an acquaintance, mentioning that he might need to work his way around some weather. On the basis of the weather information obtained by the pilot and his comments regarding the weather, the pilot was aware before departure that he would likely encounter adverse weather along the planned route of flight; however, by the time the airplane encountered the weather, the pilot had been airborne for over an hour and had not requested any updated weather information from air traffic controllers. The airplane was equipped with a BF Goodrich WX-950 Stormscope, which has some ability to depict the location and frequency of lightning strikes in the vicinity of the airplane; however, the investigation could not determine if and how this equipment may have been used during the flight. The airplane was not configured to display satellite weather information on its global positioning systems.

In October 2006, the National Transportation Safety Board issued Safety Alert SA-11, "Thunderstorm Encounters," as a result of this accident and three other fatal accidents that involved in-flight encounters with severe weather. The safety alert addresses ATC involvement in these accidents. The alert also states that IFR pilots need to actively maintain awareness of severe weather along their route of flight, and it provides suggestions to assist pilots in avoiding involvement in similar accidents. The safety alert can be found at the Safety Board's Web site at http://www.ntsb.gov/alerts/SA_011.pdf.

A scott Crossfield