Engine Failure Event
After takeoff, the pilot was cleared to climb to 6,000 feet MSL. While passing through approximately 5,000 feet, a loud noise described as a "BAM" was heard, coinciding with a loss of power from the left engine. The pilot shut down the left engine and feathered the propeller. A landing was subsequently performed without further complications.
Investigation Findings
Examination of the left engine revealed a fatigue failure of the third stage turbine wheel. Portions of the failed wheel, propelled by centrifugal force, exited the right side of the engine case and penetrated the left side of the cabin, resulting in minor damage to the aircraft.
Chain of Events
The failure of the turbine wheel created an unbalanced condition within the turbine section. This imbalance imposed an asymmetrical load on the rear main bearing support. The bearing support subsequently failed, separated from its mounting, and impacted the leading edge of the left horizontal stabilizer.