Accident Sequence
The airplane was removed from a heated hangar and refueled, at which time water droplets were visible on both wings. It remained outside for about 40 minutes without deice or anti-ice treatment before takeoff. Multiple witnesses near the accident site reported observing the airplane take off and enter a nose-high attitude, after which it immediately rolled left and impacted the terrain. Wreckage and impact signatures were consistent with the left wing impacting the runway surface before the nose of the airplane impacted terrain just to the left of the runway.
Weather and Contamination
Witnesses characterized the precipitation at the time of the accident as snow and misty rain, varying in intensity between light and medium. At the accident time, and in the three hours before, light snow, mist, instrument flight rules (IFR) ceilings, and a temperature of -1°C were reported at the departure airport. Witnesses reported that around the time of the accident light snowfall with freezing mist existed, which would have allowed for accumulation of ice on the upper surfaces of the wings, fuselage, and tail surfaces during the 40 minutes the airplane was outside.
Aircraft Systems
The airplane was equipped with a Wing and Horizontal Stabilizer Anti-Icing System to prevent and remove ice formation on the leading edges. The system is activated by a "Wing Stab" switch. Based on witness statements and flight data from the Cockpit Voice Data Recorder (CVDR) and Flight Data Recorder (FDR), the Wing Stab ice switch was turned on about nine minutes after engine start while the pilot was performing his checklist, but it was turned off shortly thereafter. The recorded position of the switch remained off through the remainder of the recorded data. Postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The anti-ice system valves and controller were tested and functioned normally. The switch was found in the on position after the accident, but the panel had separated from the instrument panel with dirt and mud below the switch; it was likely moved to the on position during the accident sequence. It could not be determined why the switch was turned off.
Pilot Procedures
The airplane's pilot operating handbook (POH) stated that surfaces contaminated by ice, frozen precipitation, or frost must be deiced before departure. It also stated that the airplane must be anti-iced when the risk of freezing precipitation exists or is actually taking place. The POH further stated that the entire wing should be inspected during the pre-takeoff contamination check, not just the leading edge, and that visual inspection should be done by a crew member from the cabin, with assistance from trained personnel outside. The before-takeoff checklist included an ice accumulation check and guidance that aerodynamic surfaces must be confirmed free of frost, ice, snow, and slush before takeoff. No evidence of the pilot requesting a passenger or vocalizing that he was checking the wings for ice accumulation was heard on the CVR audio.
Investigation Findings
Given that the pilot did not obtain any deice or anti-ice services before departure, and the immediate roll to the left as the weight on wheels transitioned from ground to air, the airplane likely had some degree of ice contamination on the upper surfaces of the wings, fuselage, and tail that affected its flight characteristics.