What happened
Following takeoff, the pilot received clearance to climb to 6,000 feet mean sea level. While ascending through approximately 5,000 feet, a loud bang was heard as the left engine lost power. The pilot shut down and feathered the left engine and completed a landing without further issues.
The investigation
Examination of the aircraft revealed that the third-stage turbine wheel had failed due to fatigue. Centrifugal force propelled fragments of the wheel through the right side of the engine case, which then penetrated the left side of the cabin, causing minor damage. The failure created an unbalanced condition in the turbine section, applying an asymmetrical load to the rear main bearing support.
Findings
The bearing support subsequently failed and separated, impacting the leading edge of the left horizontal stabilizer. This mechanical cascade was initiated by the initial fatigue failure of the turbine wheel.