Failure analysis of jack attachment bolt of an aircraft

A failed jack attachment bolt belonging to an aircraft was sent to the laboratory for investigation. Examination revealed that the bolt has failed by reverse bending fatigue. No metallurgical and/or mechanical abnormalities were found responsible for the fatigue crack initiation and fatigue appears to be stress related. It is recommended that the assembly in question be subjected to inspection for identification of the reverse bending load on the jack attachment bolt and corrective measures incorporated to prevent recurrence of similar failures