What was found
DURING INSPECTION OF THE TAILBOOM, MECHANIC NOTICED A VERY FAINT DISCOLORED LINE ADJACENT TO THE GLUE LINE OF ONE FLANGE ON THE TAIL ROTOR DRIVESHAFT. FURTHER INSPECTION WITH 10X MAG GLASS REVEALED PITTING INTO THE ALUMINUM SHAFT APPROXIMATELY 30 DEGREES OF THE CIRCUMFERENCE WITH EVIDENCE OF MORE BEGINNING THE REMAINDER OF THE WAY AROUND THE SHAFT. SUSPECT A CORROSIVE REACTION TO THE GLUE OR PREPARATION FOR GLUE AT MANUFACTURE AS THIS HELICOPTER HAS NEVER BEEN OPERATED IN A HIGH CORROSIVE ENVIRONMENT. THE PART WAS INSTALLED NEW 3 YEARS EARLIER AND HAS ACCUMULATED 1237.1 HOURS.