What happened
During a tight 180-degree turn into position, the flight crew exceeded the power nosewheel steering range. This maneuver caused the nosewheel to enter a castoring state, resulting in a delay on the runway. The crew attempted to straighten the nosewheel using differential power and brakes, but these efforts were unsuccessful.
As a result, ground personnel were called to assist with the aircraft. Upon inspection, ground personnel noted that the inboard wheel of the right main landing gear (#3 wheel) appeared to be leaning against the strut. However, the co-pilot determined that the landing gear appeared normal, and the flight proceeded to depart. Shortly after liftoff, the #3 wheel fell to the ground.
The investigation
A post-accident examination was conducted to determine why the gear component separated. Investigators discovered that the axle had fractured. This fracture was caused by the degradation and failure of the #3 inner wheel bearing. Additionally, the investigation found evidence of water contamination within the wheel bearing grease.