Failed shear bolts used in the PTO shaft of an aircraft were analyzed. Examination showed that two of the bolts have fractured under overload. Fractographic study confirmed presence of shear dimples suggesting shear load on the bolts. The Fracture initiation was not associated with any metallurgical defects. The bolts showed a tempered martensitic structure. Bolt material was found to have an average hardness of 444 HV. Since no obvious material abnormalities were found responsible for the failure, it is suggested that the test rig be inspected for abnormalities, present, if any.