What happened
During the takeoff phase of flight, the Boeing 737-200 experienced a separation of the left outboard main wheel. Following the separation, the aircraft was successfully landed without any further incident.
The investigation
The investigation determined that the failure originated from the outer bearing. Evidence of heat and mechanical damage found on the component was consistent with inadequate lubrication. While investigators could not determine if pre-existing mechanical damage was present, they noted that an unknown amount of grease had migrated away from the bearing cavity during operation.
Data regarding the component's usage showed the wheel bearing had accumulated 349 landing cycles since its initial installation and 219 cycles since the last brake change. It could not be confirmed whether the bearing had been repacked with grease since its original installation.