Incident Overview
Witnesses observed the left wing of an airplane separate as the pilot was maneuvering at approximately 1,000 feet above ground level. Subsequent examination of the wreckage revealed that the lower lift strut attachment bolt had slipped out of the attachment lug, deformed, and separated in positive bending overload. The corresponding attachment nut had either backed off the bolt or had never been installed; it was not found during an extensive search of the wreckage and accident site.
Maintenance History
Maintenance log entries indicated that the airplane had been rebuilt and the lift struts re-attached by a mechanic holding inspection authorization. This rebuild occurred 2 years and 70 flight hours before the incident. The airplane subsequently received an annual inspection approximately 6 flight hours before the incident, performed by another mechanic with inspection authorization; no discrepancies were noted.
Examination of Opposite Wing Hardware
The bolt and nut from the opposite wing were examined and revealed that the self-locking nut was not properly engaged on the bolt. This finding suggested that similar installation deficiencies may have existed on both wing attach assemblies.
Wreckage Examination Findings
Detailed examination confirmed that the left wing separation resulted from the failure of the lower lift strut attachment. The bolt had deformed and separated due to overload after slipping out of the attachment lug. The absence of the nut, combined with the improper engagement of the nut on the opposite wing, indicated a failure to properly secure the attachment hardware during the rebuild process or subsequent maintenance.