Accident Sequence
According to the pilot's report, while descending through clouds and beginning an instrument approach, the aircraft accumulated some ice on the wings. The pilot actuated the deice boots twice and observed them functioning normally on the wings, but could not see the tail. Subsequently, the elevator began to shake, and the pilot lost elevator control. He applied forward pressure on the yoke and trimmed nose-down to avoid a stall. No cockpit caution indications were present, and the pilot had disengaged the autopilot before the descent. The airplane descended through the clouds and impacted a tree before coming to rest upright in a grass area.
Examination Findings
Postaccident examination of the wreckage, including component testing of the deice system, did not reveal any preimpact mechanical malfunctions. The flap jackscrew position suggested that the flaps were likely in transit between 0° and 10° flap extension at the time of impact. Review of radar data indicated that during the two minutes before the accident, the airplane's groundspeed averaged about 82 knots, which equated to an approximate average airspeed of 94 knots when accounting for winds aloft. Current weather observations and forecast products indicated that the airplane was likely operating in an area where moderate and potentially greater structural icing conditions prevailed, with the potential for supercooled liquid droplets. The pilot operating handbook for the airplane specified a minimum speed of 130 knots indicated airspeed for flight in icing conditions.
Probable Cause
The probable cause was the pilot’s failure to maintain the minimum airspeed for flight in icing conditions, which resulted in a loss of elevator control during approach due to ice accumulation.