EXPERIMENTAL FAILURE INVESTIGATION OF AN AIRCRAFT NOSE LANDINGGEAR

In 1994, sets of aircraft were introduced into the Nigerian Aviation Industry for training of pilots. The nose wheels of some of the aircraft collapsed particularly during hard landings. The failure modes include complete fracture of the landing gear from the firewall and the buckling. This is the thrust for this study which is aimed at ascertaining the cause and mechanism of failure experimentally with a view to preventing future occurrence. Fractography of the failed samples was carried out and the fractograph showed high energy fracture – beach marks, initiation sites and the propagation area on the failure surface which indicates fatigue failure. Chemical analysis of the landing gear component showed medium carbon steel of the tough grade instead of spring steel. Experimental analysis entailed the characterization of fractured parts of the undamaged and failed nose wheel struts by determining the mechanical properties and examining the structural morphology of test samples. Fatigue tests revealed high cycle low stress fatigue in the failed material. Microstructural examination showed intermetallic inclusions within the microstructure of the material which acted as stress raisers causing crack initiation and eventually fatigue fracture.