What was found
MOST ALL MINI-500 AIRFRAMES HAVE CRACKED NEAR THE MAIN ROTOR GEARBOX MOUNT BOLT HOLES. ALL ARE LOW TIME ANYWHERE FROM 6 HOURS AND UP. AIR FRAME TUBE STRUCTURE MAY BE OF TOO THIN MATERIAL. SUBMITTER BELIEVES CRACKS FORM BECAUSE OF THE INABILITY TO TRACK AND BALANCE ROTOR BECAUSE OF A FLAW IN THE MAIN ROTOR MAST. THE INSIDE OF MAST IS NOT CONCENTRIC WITH THE OUTSIDE. THE LOWER SWASHPLATE ATTACHES TO THE INSIDE OF SHAFT AND NOW HAS A SEVERE WOBBLE SINCE IT IS NOT CONCENTRIC. THIS AIRCRAFT, SN 0222, CONTINUES TO CRACK EVEN AFTER APPROVED REPAIRS.