NTSB Identification: SEA91LA212.
The docket is stored on NTSB microfiche number 44467.
Accident occurred Sunday, August 18, 1991 in NIMROD, OR
Probable Cause Approval Date: 05/07/1993
Aircraft: CESSNA U206F, registration: N35831
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

WHILE IN CRUISE FLIGHT THE ENGINE BEGAN RUNNING ROUGH AND ULTIMATELY SEIZED. THE PILOT EXECUTED A FORCED LANDING DURING DARK NIGHT CONDITIONS ONTO ROUGH AND UNEVEN TERRAIN WITHIN A LOGGING CLEARCUT AREA. DURING THE ROLLOUT THE NOSE GEAR WAS SHEARED OFF AND THE AIRCRAFT NOSED OVER TO AN INVERTED POSITION RESULTING IN SUBSTANTIAL DAMAGE. SUBSEQUENT DISASSEMBLY OF THE ENGINE REVEALED A FATIGUE CRACK WHICH GENERATED INTO A FRACTURE OF THE CRANKSHAFT. THE CRACK WAS OBSERVED TO EMANATE FROM THE OIL TUBE PASSAGE HOLE IN THE NUMBER FOUR SHORT CHEEK OF THE CRANKSHAFT.

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

THE FRACTURED CRANKSHAFT RESULTING IN ENGINE SEIZURE FOLLOWED BY A FORCED LANDING ON ROUGH AND UNEVEN TERRAIN RESULTING IN SEPARATION OF THE NOSE GEAR.

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