Incident Overview
During a night approach to Bugulma Airport, the left propeller of the aircraft autofeathered. This caused the aircraft's speed to drop and it began to veer to the left. The crew attempted to maintain directional control, but the speed continued to decrease. At a speed of 140 km/h, the aircraft banked left to an angle of 110°, then stalled and crashed in a field located 8 km from the runway threshold and 500 meters from the extended centerline.
Damage and Occupants
The aircraft was totally destroyed. All 38 occupants on board were killed.
Probable Cause
According to the official investigation, the left propeller autofeathered one second after the flaps were deployed at an angle of 38° because an electrical switch connected to the automatic feathering system failed. This situation affected the aircraft's stability and controllability, and the crew was unable to correct abnormal yaw and roll following several errors.