TULSA, OK, USA
N7732J
PIPER PA-32-260
WHILE ON FINAL, THE ENGINE QUIT WITHOUT WARNING AND THE PILOT WAS FORCED TO EXECUTE A FORCED LANDING INTO A HEAVILY WOODED BIRD SANCTUARY. EXAMINATION OF THE ENGINE REVEALED THAT THE CRANKSHAFT GEAR ATTACHMENT BOLT WAS LOOSE WITH 0.196 INCHES OF PLAY AND THE DOWEL PIN WAS SHEARED. GEAR INSTALLATION INSTRUCTIONS CALLED FOR THE GEAR TO BE SEATED WITH A DRIFT AND HAMMER WITH NO MORE THAN 0.001 INCHES OF CLEARANCE. OTHERWISE, THE DOWEL PIN WOULD BE OFFSET AND WORK. BOTH THE BOLT AND THE DOWEL PIN SHOWED EVIDENCE OF WORKING. SHEARING OF THE CRANKSHAFT DOWEL PIN WOULD HAVE RELEASED THE GEAR TO ROTATE ABOUT THE BOLT, THUS DISCONNECTING THE GEAR AND THE IDLER GEARS WHICH TRANSMITTED TORQUE TO THE MAGNETOS. SECONDARY DAMAGE WAS OBSERVED IN THE LEFT MAGNETO. MAINTENANCE RECORDS INDICATED THAT THE ENGINE HAD BEEN OVERHAULED 88.7 HOURS PRIOR TO THE ACCIDENT.
AN ENGINE FAILURE DUE TO A DISCONNECT IN THE MAGNETO DRIVE TRAIN CAUSED BY THE CRANKSHAFT GEAR NOT BEING PROPERLY INSTALLED AND SECURED DURING A RECENT ENGINE OVERHAUL.
Source: NTSB Aviation Accident Database
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