CALLAHAN, FL, USA
N9080T
Continental Copters MK6B
WHILE MANEUVERING THE HELICOPTER DURING AN AERIAL APPLICATION FLT THE ENG QUIT. DURING THE AUTOROTATIVE LANDING THE HELICOPTER LANDED HARD. EXAMINATION OF THE ENG REVEALED THE ACCESSORY DRIVE GEAR, WHICH IS ATTACHED TO THE CRANKSHAFT BY 6 AN-4A BOLTS WITH THE TORQUE TRANSMITTED TO THE GEAR THROUGH 3 PRESS-FIT DOWEL PINS, SEPARATED WHEN THE BOLTS FAILED DUE TO FATIGUE, RESULTING IN THE TOTAL LOSS OF ENG POWER. THERE WAS NO EVIDENCE THAT THE DOWEL PINS WERE INSTALLED. ACCORDING TO THE ENG MANUFACTURER, THE DOWEL PINS ARE THE PRINCIPAL TORQUE CARRYING MECHANISM OF THE ACCESSORY DRIVE GEAR.
Source: NTSB Aviation Accident Database
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