NTSB Identification: NYC99LA202.
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Accident occurred Sunday, August 15, 1999 in PRATTSBURG, NY
Probable Cause Approval Date: 08/13/2001
Aircraft: Mooney M20E, registration: N3243F
Injuries: 2 Serious.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

About 20 minutes into the flight, the pilot heard a loud bang, then saw an object go by the windshield. The airplane started to shake so badly that the door popped open, and oil appeared on the windshield. The pilot shut down the engine, the shaking ceased, and the pilot performed a forced landing to a hilly field. Post-flight examination revealed that approximately 27 inches of one propeller blade was missing. Examination of the remaining fracture surface revealed features typical of fatigue cracking, and metallographic examination of the origin area revealed the grain structure and the presence of intergranular corrosion cracks. Review of maintenance logbooks failed to reveal any indication of 'prop strike,' overspeed, or any other catastrophic event to the propeller. On August 20, 1989, the propeller was removed for overhaul, and for compliance with AD 77-12-06. Since then, it had logged about 530 hours of operation. There were no requirements for mandatory propeller corrosion inspections.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Propeller blade separation, resulting from fatigue cracking initiated by intergranular corrosion. A factor was the lack of propeller blade corrosion inspection requirements.

Full narrative available

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