Background
The airplane was removed from an unheated hangar during a period of moderate snowfall. Approximately 15 minutes later, the instrument-rated pilot taxied the airplane to the runway for departure. Visible snow accumulation was present on the ground, as well as on the airplane's wings and horizontal stabilizer. The airplane was equipped with wing surface deice boots; however, deice boots are designed to dislodge ice that may accumulate while in flight.
According to the airplane's pilot operating handbook, all snow, frost, and ice must be removed from all wing and control surfaces during the preflight inspection. Additionally, on icy or snow-covered runways, anti-icing fluid must be sprayed on the wings, control surfaces, and in landing gear wells shortly before takeoff. The departure airport did not offer de-icing or anti-icing services.
A 2018 service letter (SL) from the airplane manufacturer further outlined the risks of snow and ice accumulation on control surfaces. The SL stated that takeoffs with snow or ice adhering to the wings should not be attempted because this could drastically affect performance due to reduced aerodynamic lift and increased drag resulting from disturbed airflow. The SL also provided recommendations to assist operators in checking proper implementation of on-ground de-icing or anti-icing procedures.
Event Description
The airport manager, who watched the airplane take off, reported that the departure appeared normal until the left wing dropped shortly after rotation. Another witness stated that the airplane was loud and low, and that it was in a left-wing-low attitude before it cleared a line of trees and then impacted the ground. The airplane was destroyed by impact forces and a postimpact fire.
Examination
Examination of the wreckage did not reveal preimpact anomalies that would have precluded normal operations. Signatures on the engine and propeller were consistent with power and rotation at the time of the accident. The impact and fire damage precluded functional testing of the flight controls and related systems. The left wing dropping during the climb was likely the result of snow accumulation on the airplane surfaces; the reduced aerodynamic lift and increased drag resulted in an aerodynamic stall and loss of control during the attempted climb after takeoff.
Probable Cause
The official probable cause, as determined by the investigation, was the pilot's decision to take off with ice/snow contamination on the airplane's wings, which resulted in an aerodynamic stall and impact with terrain.