What happened
While performing a cross-country flight, the pilot of a twin-engine airplane notified air traffic control that one engine had failed. During the aircraft's turn toward the closest airport, an observer noted that the right engine was partially detached from its lower mounts. The aircraft subsequently struck trees roughly one mile before reaching the runway threshold.
Findings
Investigation of the right engine propeller showed that a single propeller blade had broken mid-span, with the tip section missing. A metallurgical analysis determined that the failure was caused by a fatigue crack that began at corrosion pits located on the blade's camber surface.
Although the propeller had undergone an inspection approximately six hours before the crash to comply with airworthiness directive AD 81-13-06 R2, that specific directive only required checking the blade fillet and shank areas, which were located inward from the actual fracture site. While manufacturer guidelines suggest grinding blades during overhaul to eliminate visible corrosion, the aircraft owner stated the propellers had not been overhauled in the eight years of his ownership. Because the maintenance logs were destroyed in the crash, the exact timing of the last overhaul could not be verified. The aircraft was operating under Part 91 regulations, which do not mandate specific overhaul intervals for the propellers.