Accident Sequence
While descending, the pilot noted a slight vibration when the throttle was reduced. He then felt a jolt, and the windscreen became covered with oil. The pilot reduced the throttle to idle and initiated a descent for a forced landing in a field. During the descent, the left wing collided with a tree. The airplane then touched down gear up in the field, bounced, and came to rest upright.
Post-Accident Examination
Post-accident examination revealed that the No. 1 propeller blade was fractured, with only a segment of that blade remaining inside the propeller hub. The No. 2 propeller blade outer bearing race was cracked, and fretting was noted on the face of the propeller hub. Metallurgical examination of the fractured propeller blade showed evidence of fatigue, with no evidence of corrosion or mechanical damage. The No. 2 propeller blade outer bearing race was cracked due to overstress. Examination of the propeller hub revealed severe fretting inboard of the attach bolts and evidence of gouging on the pilot bore.
Maintenance Records
Review of the maintenance records disclosed that the propeller was last installed on July 15, 1997. At the time of the propeller blade fracture, it had accumulated 150.81 hours since the last installation.