Incident Overview
During takeoff, the #2 wheel separated from the left main landing gear assembly of the aircraft. The incident occurred after a company mechanic had replaced the tire on that wheel during a pre-flight inspection.
Preceding Maintenance Actions
A company mechanic performing a walk-around inspection noted that the #1 and #2 main landing gear tires required replacement. Both tires are located on the left main landing gear assembly, with the #1 tire positioned outboard of the #2 tire. The mechanic reported that the #2 main landing gear tire was removed and replaced, and stated that nothing unusual occurred during the tire change.
Evidence Found After Separation
Following the wheel separation, the axle nut/spacer assembly was found with the wheel. The axle nut lock-bolts were installed in the axle nut/spacer assembly, with safety wire connecting the lock-bolts to the axle nut. The lock-bolts were not damaged. The interfacing threads between the axle nut/spacer assembly and the axle were not stripped, and the threads showed no signs of wear.
Post-Incident Examination
At the request of the National Transportation Safety Board, a demonstration of a wheel installation and a review of the installation procedures were performed. The demonstration indicated that for the lock-bolts to engage the axle keyslot, the axle nut/spacer assembly had to be properly torqued and the wheel bearings seated.