NTSB Identification: SEA98LA158.
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Accident occurred Friday, August 07, 1998 in YELLOWPINE, ID
Probable Cause Approval Date: 01/11/2000
Aircraft: Cessna 182, registration: N6437A
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.
Upon landing the pilot heard a bang and the right wing dropped. The airplane incurred substantial damage during a ground loop maneuver, following the separation of the right main wheel and lower strut end immediately after touchdown. Post-crash examination revealed that the lower end of the right main landing gear spring strut had broken off. Examination of the fracture surfaces revealed features characteristic of fatigue cracking in multiple locations. The fatigue cracks originated at the surface of the holes, at the edge between the wall of the hole and flat face of the leg. Separation of the spring strut was caused by fatigue cracks that originated from the surface of the two upper holes. No chamfer was found at the surfaces of the two upper holes. The surface of these holes contained for the most part a corner edge that is a stress raiser and, in turn, this stress raiser sensitized the hole to cracking. The two upper holes most likely were drilled oversize to remove anomalies such as corrosion or fretting damage. The diameter of the oversize holes was sufficient to have removed evidence of the chamfer. There was no airframe log information available which identified any maintenance on the spring strut.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Right main landing gear spring strut fatigue, improper maintenance, and subsequent separation of the strut end. Full narrative available
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