What happened
The aircraft experienced an in-flight engine failure while operating. Following the power loss, the pilot initiated procedures to manage the emergency, which included releasing an external load that had been carried. Despite these efforts, the situation deteriorated rapidly due to the specific circumstances of the failure.
The pilot attempted to perform an autorotation to land safely without engine power. However, the maneuver could not be completed successfully. The aircraft struck trees during this attempt. The primary factors preventing a safe landing were insufficient altitude remaining after the failure and terrain conditions that were unsuitable for the emergency landing approach.
The investigation
Examination of the failed components revealed the root cause of the power loss. Technical analysis identified a structural failure within the engine assembly. Specifically, the investigation found a fatigue fracture in blade number 19 of the second stage turbine rotor assembly. This mechanical failure led directly to the cessation of engine operation.
Findings
The sequence of events was driven by the mechanical failure of the turbine component. The pilot's actions to drop the external load were appropriate for the phase of flight, but the remaining altitude was inadequate to execute a successful autorotation given the terrain constraints. The combination of the sudden power loss and the unsuitable terrain resulted in the collision with trees.