What was found
TAIL ROTOR DRIVE YOKE PN C908-1 REV K LOT 220 LOST A MAGNET THAT PHASES WITH THE HALL EFFECT SENSORS TO PROVIDE MAIN ROTOR RPM. THIS RESULTED IN THE FAILURE OF THE MAIN ROTOR RPM SYSTEM AND CAUSED AN ABORTED FLIGHT AND RECOVERY OF PASSENGERS WITH ANOTHER AIRCRAFT. THE YOKE WAS INSPECTED AND IT WAS FOUND THAT THE RIVET THAT HOLDS THE MAGNET ON THE YOKE WAS NOT PROPERLY INSTALLED CAUSING THE SEPARATION OF THE MAGNET FROM THE YOKE. THE RESULT WAS 6 HOURS OF MAINTENANCE IN A REMOTE AREA OF ALASKA AJACENT TO HIGH TIDAL MOVEMENT. ROBOINSON QUALITY CONTROL SEEMS TO HAVE FALLEN OFF OF ITS PREVIOUS HIGH STANDARD AT THIS TIME. ALSO THE MAINTENANCE MANUAL FOR THE ROBINSON R44 SPECIAL TORQUE FOR THE INSTALLATION OF THE YOKE 7.140 AND THE INSTALLATION OF THE ROTOR BRAKE ARE AT ODDS AS THE ROTORBRAKE INSTALLATION PROCEDURE 7.620 MAXIMUM TORQUE DOES NOT MEET THE MINIMUM SPECIAL TORQUE OF THE YOKE PER THE SPECIAL TORQUE CHART 23-33.