What happened
A commercial pilot was operating a business flight with 10 passengers aboard an 8-passenger airplane during a cross-country mission. While performing an instrument landing system (ILS) approach, the aircraft entered instrument meteorological conditions at 3,100 feet MSL. During this descent, ice began to build on the windshield, empennage, and the leading edges of the wings. The pilot utilized pneumatic deice boots several times and reduced the airspeed to 120 knots.
As the aircraft descended through 400 feet AGL, it emerged from the clouds. While flying over the airport perimeter, the pilot maintained a speed of 120 knots with normal landing indications. However, at approximately 100 feet AGL, the aircraft began a rightward veer. Despite the pilot's attempts to correct with left-hand inputs and an attempt to execute a go-around via increased engine power, the aircraft drifted into the grass to the right of the runway. The impact caused damage to the landing gear and wings. There were no fatalities, though the aircraft sustained significant damage.
Findings
Post-accident inspections revealed between 0.5 and 1 inch of mixed ice on the windshield, the angle of attack probe, the horizontal and vertical stabilizers, and the right wing's leading edge. Investigation into the pilot's qualifications revealed that while he was operating under a single-pilot exemption, he lacked the required 1,000 hours of turbine flight time, possessing only 500 hours.
Cockpit voice recorder analysis showed that the pilot did not verbally complete all landing or approach checklists, nor did he acknowledge the activation of anti-ice or deice systems. Radar data indicated the airspeed dropped as low as 99 knots during the final two minutes of the approach. The investigation concluded that the aerodynamic stall was caused by a combination of ice accumulation on the leading edges, a no-flap approach, and low airspeed, likely exacerbated by pilot task saturation due to insufficient flight experience for single-pilot operations in icing conditions.