What happened
During the takeoff roll of the aircraft, a ground agent observed the outboard wheel of the right main landing gear separate from the axle. Following the separation, the flight crew retracted the landing gear; however, the crew reported that they did not experience any unusual noises or vibrations during the climb.
The flight crew was notified of the wheel separation via company radio. The aircraft continued its flight to the destination airport, where a fly-by was performed which confirmed that the wheel was indeed missing. The aircraft subsequently completed a landing without incident.
The investigation
An inspection of the right main gear axle was conducted following the event. This examination revealed that the retaining nut remained attached to the axle, though minor damage was noted on the outboard side of the axle. According to the operator, the right outboard wheel of the aircraft had been replaced on the morning of the incident, and this procedure was performed without the use of a required spacer.