NTSB Identification: MIA99LA091.
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Accident occurred Thursday, February 25, 1999 in ST. CLOUD, FL
Probable Cause Approval Date: 12/04/2000
Aircraft: Mooney M20J, registration: N4671H
Injuries: 3 Uninjured.

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

While descending, the pilot noted a slight vibration when the throttle only was reduced. He then felt a jolt and the windscreen became covered with oil. He reduced the throttle to idle, initiated a descent for a forced landing in a field, and while descending, 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 revealed the No. 1 propeller blade was fractured with only a segment of that blade 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 revealed evidence of fatigue with no evidence of corrosion or mechanical damage. The No. 2 propeller blade outer bearing race was cracked due to overstrees. Examination of the propeller hub revealed severe fretting inboard of the attach bolts and evidence of gouging on the pilot bore. Review of the maintenance records revealed that the propeller was last installed July 15, 1997; and had accumulated 150.81 hours since last installation at the time of the propeller blade fracture.

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

The improper installation of the propeller by maintenance personnel resulting in fretting of the face of the propeller hub and fatigue failure of the No. 1 propeller blade. Also, the unsuitable terrain encountered during the descent for the forced landing.

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