Accident Sequence
While maneuvering at 4,000 feet above ground level, the flight crew heard a loud noise from the left engine and observed that the engine had dropped approximately 45 degrees from its normal position. The crew initiated a return to the departure airport for an emergency landing. During extension of the landing gear, the left engine dropped further. The aircraft subsequently became difficult to control directionally due to increased drag, and the crew performed a forced landing in a wooded area.
Post-Crash Examination
Examination of the wreckage revealed that the left propeller hub had failed due to fatigue cracking, which caused a blade to separate. The remainder of the propeller detached when the propeller flange failed due to overstress. The engine then dropped down after the engine mount separated due to overstress.
The left propeller had sustained damage during a gear-up landing that occurred 525 flight hours prior to the accident. At that time, the propeller blades were bent beyond repairable limits and were scrapped. The hub was inspected and returned to service with new blades. The manufacturer's procedures call for a hub to be retired if the blades receive damage beyond repairable limits and are scrapped. In this event, the hub was not retired and was instead placed back into service with new blades.