Accident Overview
A Cessna 414 aircraft collided with level ground while attempting to land during a snow shower. The pilot had declared an emergency one minute after departing under instrument flight rules and requested to return to the airport under visual flight rules. The pilot informed air traffic control that he could not gain speed. Visibility at the airport was variable, with the lowest reported visibility being half a mile. Witnesses observed the airplane traveling fast at low altitude and reported that both engines were running.
Sequence of Events
Before the flight, during servicing, pitot tube covers were not used. Approximately 1.5 inches of snow had accumulated on the airplane during refueling and was brushed off. The airplane was seen flying into a snow shower and then reversing course. Witnesses reported the airplane's bank angle reached 80 to 90 degrees with a 20-degree nose-down pitch attitude. The airplane descended into a snow-covered pasture. Witnesses noted that the airplane leveled its wings just before impact.
Investigation Findings
Investigation revealed that the pitot tube covers were not used during servicing. The manufacturer's safety and warning supplements state that inflight ice protection is not designed to remove snow on parked aircraft. The manufacturer recommends using heated hangars or approved deicing solutions to ensure no internal accumulations in pitot-static system ports. Both occupants were killed in the accident.
Probable Cause
The official probable cause is the failure of the pilot to use pitot static system covers during icing conditions, which resulted in a blocked pitot tube and subsequent loss of airspeed indications. This led to pilot disorientation and an invertant stall. Factors to the accident were improper snow removal and adverse weather conditions.