Incident Description
Approximately 20 minutes after departure, the pilot heard a loud bang and observed an object pass by the windshield. The aircraft began shaking violently, causing the door to open. Oil appeared on the windshield. The pilot shut down the engine, which stopped the shaking, and executed a forced landing to a hilly field.
Post-Flight Examination
A post-flight examination revealed that approximately 27 inches of one propeller blade was missing. The remaining fracture surface exhibited features consistent with fatigue cracking. Metallographic examination of the origin area showed the grain structure and presence of intergranular corrosion cracks.
Maintenance History
Review of maintenance logbooks found no indication of a propeller strike, overspeed, or any other catastrophic event affecting the propeller. On August 20, 1989, the propeller was removed for overhaul and for compliance with AD 77-12-06. Since that overhaul, the propeller had accumulated about 530 hours of operation. There were no mandatory requirements for propeller corrosion inspections.