What happened
The aircraft was operating under instrument flight rules, approaching the airport via an Instrument Landing System (ILS) procedure. At the time of the incident, the plane was approximately four miles from the runway threshold. During this phase of the approach, a sudden failure of one of the engines occurred. The pilot attempted to execute a forced landing on a nearby frozen lake due to the loss of power. The impact with the ice surface resulted in substantial damage to the airframe.
The investigation
Following the accident, investigators conducted a detailed teardown and examination of the failed engine to determine the root cause of the malfunction. The mechanical analysis focused on the internal components of the engine to identify any signs of pre-existing defects or operational failures.
Findings
The technical examination revealed that the engine failure originated from the movement of the number 2 main bearing. This movement created a bending overload on the crankshaft, which ultimately led to the separation of the crankshaft at the number 3 cheek. The structural failure of the crankshaft was the primary factor in the loss of engine power.
Safety message
Regular inspection of engine bearings and crankshafts is critical for preventing catastrophic failures. Early detection of bearing movement or wear can help avoid in-flight engine shutdowns.