What was found
DURING A NORMAL START PROCEDURE, WITH THE NR 1 ENGINE AT GROUND IDLE AND JUST PRIOR TO THE ROTOR BRAKE BEING RELEASED, A FAILURE OCCURRED IN THE MAIN GEARBOX THAT ALLOWED MOMENTARY ROTATION AND SUBSEQUENT LOCKING OF THE MGB. THE ROTOR SYSTEM BARELY MOVED BEFORE SUDDEN STOPPAGE EVENT OCCURRED DUE TO LOCKING FORCES IN THE MGB. THE TAIL ROTOR ENGAGED MOMENTARILY AT THE TIME OF INITIAL ROTATION BEFORE AN UNDERMINED SEQUENCE OF FAILURES RESULTED IN THE NUMBER 7 DRIVESHAFT FAILED BY TWISTING OPEN, MULTIPLE COUPLINGS BEING DISTORTED IN THE TAIL ROTOR DRIVE LINE, THE TAIL ROTOR OUTPUT DRIVE FAILING AT THE MGB, DAMAGE TO THE INPUT COUPLING ON THE NR 1 MGB INPUT AND POCKET DAMAGE FOUND ON 4 OF THE 6 MAIN ROTOR BLADES ON THE TRAILING EDGE OF THE POCKETS PRIMARILY BUT NOT LIMITED TO MID SPAN LOCATIONS. THERE ARE NO PREVIOUS KNOW FAILURES OF THIS TYPE.