ALCOA, TN, USA
N3605B
S.N.I.A.S. AS350D ASTAR
WHILE PREPARING TO LAND, THE PILOT EXPERIENCED A TAIL ROTOR DRIVE FAILURE AT A SPEED OF LESS THAN 60 KNOTS. AT THAT SPEED, HE WAS UNABLE TO MAKE THE NECESSARY RIGHT TURN FROM HIS POSITION TO LAND ON THE RUNWAY. INSTEAD, HE CLIMBED ABOUT 50 FT IN A LEFT TURN TO LINE-UP FOR A RUN-ON LANDING. AS HE SLOWED TO ABOUT 20 KNOTS AT LOW ALTITUDE, THE HELICOPTER BEGAN TO YAW HARD TO THE LEFT. THE COLLECTIVE WAS LOWERED TO TOUCHDOWN BEFORE CONTROL WAS LOST. DURING THE LANDING, THE HELICOPTER BOUNCED AND ROTATED ABOUT 90 DEGREES BEFORE COMING TO REST. AN EXAMINATION REVEALED THAT THE NUMBER 4 TAIL ROTOR DRIVE SHAFT BEARING, PN 6007-2RS1MT47CA, HAD SEIZED. THE TAIL ROTOR DRIVE SHAFT AND RUBBER MOUNTING COLLAR CONTINUED TURNING UNTIL THE SEIZED BEARING CHAFFED THROUGH THE COLLAR AND ALSO THE DRIVE SHAFT ITSELF. SUBSEQUENTLY, THE TAIL ROTOR DRIVE SHAFT, PN 350A34-0110-02, SHEARED. THE TAIL ROTOR DRIVE SHAFT BEARING WAS FACTORY LUBED AND SEALED AND HAD NO RETIREMENT TIME LIMIT. THE BEARING FAILED AFTER 729 HOURS OF OPERATION.
Source: NTSB Aviation Accident Database
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