Accident Sequence
As the aircraft began to rotate during takeoff, one propeller blade separated and was thrown approximately 1000 feet behind the aircraft. The remaining blade and the hub became unbalanced, causing the engine to twist to a 45-degree angle. The pilot shut down the engine. The aircraft then traveled off the left side of the runway and cartwheeled.
Examination Findings
Inspection of the propeller revealed that the broken blade had fractured about two inches outboard of the hub. Metallurgical tests were conducted on the separated components. These tests identified numerous fatigue origins on both blade butt ends at their separation points, as well as in the propeller attachment area on the face of the hub. Additionally, the propeller blade mounting, which attaches to the engine, had broken out between two stud holes. This mounting area exhibited fatigue indications and deformation of the mounting surface.