RAYTHEON AIRCRAFT COMPANY 58 — Maxwell, NE

What happened

The pilot filed an instrument flight rules flight plan and, about an hour before departure, he obtained a weather briefing, which included an airmen's meteorological information (AIRMET) for the potential for moderate icing conditions and turbulence below 8,000 ft over the route of flight. About the time the airplane departed, weather conditions worsened with freezing fog, heavy snow fall, and reduced visibility. However, at that time, neither a significant meteorological information (SIGMET) nor a center weather advisory warning of severe icing conditions had been issued. After departure, an air traffic controller cleared the airplane to climb to 9,000 ft mean sea level (msl). When the airplane was about 7,000 ft msl and still climbing, the pilot asked the controller if there were any reports regarding the cloud tops, and the controller responded that there were not. Less than a minute later, radar data showed the airplane descending, and the pilot issued a "mayday" call. Radio and radar contact were then lost. The wreckage was found about 11 miles northeast of the airport. A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

Flight crewmembers of two flights inbound to the airport around the time of the accident reported that they encountered freezing rain and severe mixed icing; these conditions were beyond the airplane's icing certification standards and could have caused increased weight, degraded performance, and unpredictable aerodynamic characteristics. Federal Aviation Administration guidance warns that, when severe icing conditions are encountered, the pilot shall immediately request priority handling to facilitate a route or an altitude change to exit the icing conditions.

Based on the weather information, it is likely that the airplane encountered severe icing conditions about the time of the accident, which resulted in structural icing that exceeded the airplane's capabilities and resulted in a loss of control. Based on the wreckage distribution, which was consistent with a high-speed impact, and the low visibility present at the time of the accident, it is likely that, after the loss of airplane control, the pilot experienced spatial disorientation; however, there was insufficient evidence to determine the role that spatial disorientation might have played in the accident.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.