As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER A TRAINING FLIGHT, PILOT NOTIFIED MAINT OF A STRANGE NOISE THAT APPEARED TO BE EMANATING FROM THE DRIVE SYSTEM. AFTER A VISUAL OF THE MAIN AND TAIL ROTOR DRIVE SYSTEMS, A MAINT GROUND RUN WAS PERFORMED. MAINT CONFIRMED A MEDIUM TO LOW FREQUENCY NOISE RELATED TO THE A006-1 MAIN GEARBOX. THE MAIN GEARBOX CHIP DETECTOR WAS REMOVED AND FOUND COVERED WITH FERROUS. (X)