What happened
During the initial phase of a takeoff roll, a critical mechanical failure occurred on the aircraft's left engine. A portion of the propeller blade tip detached from its structure while the plane was accelerating down the runway. Approximately nine inches of the broken blade tip penetrated the upper fuselage, striking the area just behind the pilot's head.
The impact caused extensive damage to the aircraft's control systems. The flying debris severed the cables responsible for throttle, fuel mixture, carburetor heat, and propeller pitch control for the left engine. Additionally, the aileron control cable became jammed in the full left position, and the cables for the right engine sustained damage.
As the left engine lost power and dropped to idle, the pilot was forced to take immediate emergency action. To prevent further complications from the damaged engine, the pilot switched off the magnetos. This allowed the crew to abort the takeoff safely on the ground.
The investigation
Following the incident, a detailed metallurgical examination was conducted on the failed propeller component. The analysis focused on the Hartzell Model HC-C1YK-2CUF propeller, specifically part number FC8477A-4.
The examination revealed that the failure was not due to sudden overload but rather a progressive structural breakdown. The root cause was identified as fatigue, which initiated at a pre-existing dent located on the leading edge of the propeller blade. This defect allowed stress cracks to grow until the blade tip could no longer withstand the rotational forces during takeoff.
Findings
The investigation determined that the primary factor in this incident was the structural integrity of the propeller. The presence of a dent on the leading edge served as the origin point for fatigue cracking. This type of damage compromises the blade's ability to handle operational stresses, particularly during high-power phases like takeoff.
The resulting failure led to immediate loss of engine control and partial loss of flight controls due to severed cables. The jammed aileron cable further complicated the situation, though the pilot successfully managed the emergency by aborting the takeoff before leaving the ground.