ZILLAH, WA, USA
N11VH
BELL 47G-2
EN ROUTE TO THE LOCAL SPRAY AREA A TOTAL LOSS OF POWER OCCURRED ALONG WITH A LOSS OF OIL PRESSURE. THE ACFT WAS APRX 200 FT AGL OVER A PEAR ORCHARD. THE PLT WAS ATTEMPTING TO AUTOROTATE ONTO A NEARBY ROAD BUT THE LEFT SKID CAUGHT THE ROOF TOP OF A METAL SHED. THE HELICOPTER CRASHED THROUGH THE ROOF OF THE SHED AND ROLLED OVER ONTO ITS SIDE. INVESTIGATION REVEALED THAT THE NUMBER THREE CYLINDER ROD BOLT HAD FAILED. METALLURGICAL EXAM REVEALED THAT THE NUMBER 3 CYLINDER CONNECTING ROD CAP HAD FAILED AS A RESULT OF OVERSTRESS FORCES DUE TO EXCESSIVE HEATING OF THE ROD AND CAP. FAILURE OF THE NUMBER 3 CYLINDER CONNECTING ROD BOLT WAS DUE TO FATIGUE CRACKING. THE MOST LIKELY CAUSE OF THE OVERHEATING WAS DUE TO A DETERIORATED BEARING.
Source: NTSB Aviation Accident Database
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