What happened
During an instrument landing system (ILS) approach, the flight crew observed an anomaly where the flight director indicated a climbing right turn, even though the aircraft was still following the localizer and glideslope. At the time, the aircraft's ice protection systems were active, though no ice was visible on the airframe. Upon disconnecting the autopilot, the aircraft experienced a sudden roll to the right. The crew attempted to recover by increasing engine power and applying corrective control inputs, but the aircraft struck the ground in a nearly level wing attitude.
Data from ADS-B tracking confirmed that the aircraft was descending on the correct glidepath but allowed its speed to drop below the target of 130 knots. As the airspeed decreased to approximately 102 knots, the aircraft began a slight right roll. The speed continued to decline below 100 knots, at which point the aircraft reached a 27-degree right bank. Following this, the descent rate accelerated to more than 4,000 feet per minute, and the aircraft rolled sharply to the left before the impact.
Findings
Post-accident investigations of the engines and primary flight controls showed no mechanical defects. While the yaw damper system was found to be inoperative, this component was an optional feature and not essential for flight. Some deficiencies were noted in the remaining autopilot components, but these were not sufficient to cause a total failure of the automatic flight control system.
Analysis concluded that the aircraft suffered an aerodynamic stall caused by the airspeed falling below critical levels. The investigation suggests the crew may have become fixated on the erroneous flight director indications, leading to a loss of airspeed control. While the flight director error could not be physically replicated during the component examination, the decay in airspeed was the primary factor leading to the stall.