NTSB Identification: ANC92FA005
Accident occurred Tuesday, October 15, 1991 in MONTAGUE ISLAND, AK
Probable Cause Approval Date: 05/03/1993
Aircraft: PIPER PA-18, registration: N3850Z
Injuries: 1 Minor.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

DURING CRUISE FLIGHT, THE ENGINE SEIZED WITHOUT WARNING. WITH NO SUITABLE LANDING AREA ON THE BEACH, THE PILOT DITCHED IN THE OCEAN AND SWAM ASHORE ABOUT 1/2 MILE AWAY. AN INVESTIGATION REVEALED THAT THE CRANKSHAFT HAD BROKEN AT THE FORWARD CHEEK OF THE #3 MAIN BEARING. A REDDISH SEALANT RESIDUE WAS FOUND AROUND THE MAIN BEARING THRU STUD HOLES OF THE CRANKCASE. ACCORDING TO LYCOMING SERVICE INSTRUCTION #1125A, SEALANT SHOULD NOT HAVE BEEN APPLIED IN THIS AREA.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE POWER LOSS DUE TO THE CRANKSHAFT FAILURE. CONTRIBUTING TO THE ACCIDENT WAS IMPROPER MAINTENANCE DURING THE LAST ENGINE OVERHAUL.

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