Failure analysis of main landing gear axle of an aircraft

Item part No. R35/001-150-35002(A) LH main gear assembly Sl. No. 106L of an aircraft was sent to the laboratory for investigation. The main landing gear axle had fractured at the threaded region resulting in dislodgement of the main wheel assembly. Fractographic examination confirmed that the axle had fractured by torsional overload. The torsional load resulted due to seizure of the front bearing. Evidences suggest that the causative factor for the bearing seizure was high axial loads. The reason for such high axial loads on the bearing needs to be established. The axle material was found to conform to MIL-S-6758 specification