VOLCANO, HI, USA
N35970
AEROSPATIALE AS350D
THE VFR SIGHT-SEEING FLIGHT WAS BEING CONDUCTED UNER 14 CFR 135. WHILE DESCENDING INTO A MOUNTAINOUS AREA THE PILOT FELT A SEVERE VIBRATION ABT 10 - 15 SECONDS BEFORE THE ENGINE FAILED. THE PLT EXECUTED AN AUTOROTATION IN THE UPWARD SLOPING TERRAIN AND THE HELICOPTER ROLLED-OVER ON TOUCHDOWN. THE ENGINE EXAM DSCLSD THAT THE POWER TURBINE SHAFT AND THE NOS. 2 & 3 BEARINGS FAILED DUE TO OIL STARVATION AND DISPLAYED EXTREME HIGH TEMPERATURE DISTRESS. THE CHIP DETECTOR O-RING SEAL WAS EXCESSIVELY WORN. OIL RESIDUE STREAKING WAS FOUND ON THE OUTSIDE OF THE FUSELAGE/ TAILCONE ASSY AND THE VERTICAL/HORIZONTAL STABILIZERS.
A CATASTROPHIC FAILURE OF THE POWER TURBINE SHAFT AND BEARINGS. THE FAILURE WAS A RESULT OF OIL STARVATION DUE TO AN EXCESSIVELY WORN CHIP DETECTOR O-RING SEAL,INADEQUATE MAINTENANCE AND PREFLIGHT. CONTRIBUTING FACTOR(S) WAS: THE MOUNTAINOUS TERRAIN.
Source: NTSB Aviation Accident Database
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