CHARLESTON, WV, USA
N4749R
BELL 47G-4A
DURING AN APPROACH TO LAND, THE ENGINE LOST POWER AT APRX 500 FT AGL. THE PLT REPORTED THAT DURING AN AUTOROTATIVE LANDING, HE HAD TO MANEUVER TO AVOID TREES & A RIDGE IN ORDER TO LAND IN A SUITABLE AREA. DURING THIS TIME, ROTOR RPM DROPPED & A CRASH LANDING OCCURRED. A TEARDOWN OF THE ENGINE REVEALED THAT THE TIMING GEAR, PN 67687, HAD FAILED & A TOOTH HAD SEPARATED. ALSO, THE WOODRUFF KEY, PN STD-858, HAD FAILED. A METALURGICAL EXAMINATION REVEALED EVIDENCE OF FATIGUE ON BOTH PARTS. FAILURE OF THE TIMING GEAR ORIGINATED AT AN INNER CORNER OR THE GEAR KEYWAY. THE ENGINE HAD ACCUMULATED 613 HRS OF FLT TIME SINCE MAJOR OVERHAUL.
Source: NTSB Aviation Accident Database
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