Fatigue Fracture of a C130 Aircraft Main Landing Gear Wheel Flange

A piece of wheel flange separated from the main landing gear wheel of a C130 aircraft as it taxied on a runway. The wheel was a 2014-T61 aluminum alloy forging and had been in service nearly 20 years. Fractographic evidence indicated that the initial crack growth was caused by high-cycle fatigue. The crack grew to approximately 8 in. in length before final catastrophic fracture. Fatigue analyses accurately predicted the cyclic life demonstrated by the failed wheel since its last inspection, assuming an initial crack length of 13 to 25 mm (0.5 to 1.0 in.). It was recommended that the inspection interval be reduced to one-third of its original duration for the current level of inspection reliability, or that inspection procedures be improved in order that cracks substantially smaller than 13 mm (0.5 in.) can be reliably detected.