What was found
PART IN QUESTION IS LOCATED ON THE AFT MOST SECTION ON THE HELICOPTER TAIL BOOM. THE TAIL ROTOR GEARBOX AFT MOUNT STUDS PASS THROUGH THE TOP OF THIS FITTING ON THE LEFT AND RIGHT SIDES. CRACKS DEVELOPED FROM THESE STUD HOLES TO ADJACENT MOUNTING RIVET HOLES. ALSO, CRACKS WERE NOTED ON THE TOP SIDE OF THIS FITING THAT WERE NOT VISIBLE WITH FITTING INSTALLED. CRACKS WERE FOUND DURING NORMAL 100-HOUR INSPECTION. POSSIBLE CAUSE CAN BE UNDER OR OVER TORQUING OF INSTALLATION HARDWARE, OR EXCESSIVE TAIL ROTOR VIBRATIONS. (X)