NTSB Identification: SEA99LA063.
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Accident occurred Saturday, May 15, 1999 in COEUR D'ALENE, ID
Probable Cause Approval Date: 11/30/2000
Aircraft: Lake LA-4, registration: N152WB
Injuries: 2 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 landing in variable, shifting winds, both the dual student and the instructor had trouble maintaining directional control of the aircraft. After touchdown, the aircraft started turning toward the right side of the runway, and the instructor could not get it to straighten out using maximum left brake and full left rudder. He therefore added power to get airflow over the rudder to increase its efficiency, but the aircraft continued to turn sharper, eventually departing the right side of the runway and impacting the segmented circle at the base of the wind sock. It was later discovered that an improper repair weld on one of the engine pylon mounting straps had failed from fatigue, allowing the engine pylon to twist out of alignment with the longitudinal axis of the aircraft.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fatigue failure of a repair weld on one of the engine pylon mount straps and the resultant reduction in directional control. Factors include an inadequate repair of the strap, variable wind speeds and sudden wind shifts. Full narrative available
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