What was found
THE NR 4 MAIN WHEEL SEPARATED FROM AIRCRAFT DURING TAXI IN. MAINTENANCE FOUND THE AXLE SHEARED OFF, NO OTHER AIRCRAFT DAMAGE WAS FOUND. THE RT MLG INNER CYLINDER WAS REMOVED AND REPLACED IAW MM 32-11-21 AND 12-15-31. *S/D* INVESTIGATION BY ENGINEERING CONCLUDED THAT THE CAUSE OF MAIN WHEEL SEPARATION WAS DUE TO A CRACK WHICH STARTED AT BRAKE FLANGE BOLT HOLE. STRESS CORROSION CRACKING IS SUSPECT.