On May 15, 1999, a Lake LA-4 (registration N152WB) operated by Mike D. Kincaid was involved in an aviation accident near Coeur D'alene, ID. Investigators recorded the probable cause as: An improper repair weld on one of the engine pylon mounting straps failed from fatigue, allowing the engine pylon to twist out of alignment with the longitudinal axis of the aircraft. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During landing in shifting winds, an aircraft veered right despite corrective inputs. An improper weld repair on the engine pylon mounting strap failed, causing misalignment and loss of directional control.
Incident Summary
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. The instructor applied maximum left brake and full left rudder, but could not straighten the aircraft. He then added power to increase airflow over the rudder for greater efficiency, but the aircraft continued to turn more sharply. It eventually departed the right side of the runway and impacted the segmented circle at the base of the wind sock.
Discovery of Cause
Subsequent inspection revealed that an improper repair weld on one of the engine pylon mounting straps had failed from fatigue. This failure allowed the engine pylon to twist out of alignment with the longitudinal axis of the aircraft. The misalignment compromised directional control, contributing to the runway excursion.
Probable cause
An improper repair weld on one of the engine pylon mounting straps failed from fatigue, allowing the engine pylon to twist out of alignment with the longitudinal axis of the aircraft.