DE KALB, IL, USA
N8642F
HUGHES 269C
WHILE RETURNING FROM A POWER LINE PATROL THE ENGINE LOST POWER AND AN AUTOROTATION WAS MADE INTO TREES. THE #4 CONNECTING ROD FRACTURED THROUGH THE BEARING STRAP ON ONE SIDE AND PUNCTURED A HOLE IN THE CRANKCASE. SAFETY BOARD METALLURGICAL EXAMINATION REVEALED FATIGUE BEACH MARKINGS ON THE MAJORITY OF THE FRACTURE SURFACE. ADDITIONAL EXAMINATION SHOWED DETERIORATION OF THE CENTER MAIN BEARINGS AND THE FAILURE OF THE TOP RING ON THE #1 PISTON. THE RING FAILURE HAD WORN A GROOVE IN THE PISTON ALMOST THROUGH TO THE 2ND RING GROOVE. SPARK PLUGS WERE NORMAL EXCEPT FOR OIL DEPOSITS ON THE #1 CYLINDER PLUGS. PILOT STATED THAT HE HAD ADDED 3 QTS OF OIL DURING REFUELING DAY OF ACCIDENT.
FATIGUE FAILURE OF THE NUMBER FOUR CONNECTING ROD WHICH RESULTED IN AN ENGINE FAILURE. FACTORS IN THE ACCIDENT WERE THE BROKEN RING IN THE NUMBER ONE PISTON AND A DETERIORATED CENTER MAIN BEARING.
Source: NTSB Aviation Accident Database
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