Event Details
Before departure, a briefer at the San Angelo Automated Flight Service Station (AFSS) informed the pilot that computers in south Texas were inoperative for 1.5 hours and that no current weather information was available. Although current weather data could be obtained from the National Weather Service at Midland and Flight Service Stations at Midland, McAlester, and De Ridder, the pilot did not contact those facilities, nor did the briefer advise him to do so. The pilot also did not update weather conditions during the flight.
Weather Information
Instrument meteorological conditions (IMC) existed above 12,500 feet. The freezing level was forecast between 10,000 and 12,000 feet. The area through which the aircraft flew was conducive to potential icing.
Flight Progress
Approximately 38 minutes after takeoff, the aircraft indicated a reduction in ground speed from 270 knots to 150 knots over four minutes. In the subsequent 12 seconds, the speed further decreased to 100 knots. About 33 seconds before reaching 100 knots, the pilot requested a descent from 15,000 feet to 13,000 feet. At that time, the true ground track was approximately 080°, with reported winds aloft from 213° at 43 knots.
Final Descent
Before air traffic control could clear the descent, the aircraft began descending. Radar contact was maintained until the aircraft reached 14,800 feet, then lost after a single return at 9,700 feet. The descent rate between the last two recorded altitudes was 12,750 feet per minute.
Post-Accident Investigation
Examination of the wreckage revealed no preimpact mechanical malfunction. The aircraft was certified for flight into known icing conditions, but the status of anti-icing or deicing equipment could not be determined because of impact and fire damage. Toxicological samples from all five occupants contained low levels of ethanol; however, evidence indicated the samples were unreliable. All occupants were killed in the accident.
Probable Cause
The official probable cause is improper planning and decision-making by the pilot, which resulted in excessive accumulation of structural icing on the aircraft's wings, stabilizers, fuselage, and/or engine inlets, and his failure to maintain adequate airspeed and aircraft control. Contributing factors include the pilot's inadequate weather evaluation due to lack of available information at the automated flight service station, his failure to obtain additional information from other weather stations either before takeoff or during the flight, his lack of experience in this make and model of aircraft, and icing conditions at cruise altitude.