COKEVILLE, WY, USA
N78599
PIPER PA-12
THE PILOT OF THE PIPER PA 12 REALIZED THAT HE WAS EXPERIENCING A POWER LOSS WHILE MANEUVERING, LOOKING FOR MISSING SHEEP. HE TURNED TO LOWER, FLATTER TERRAIN. THE ENGINE CONTINUED TO LOSE POWER, SO HE MADE A FORCED LANDING IN UNSUITABLE TERRAIN. THE AIRCRAFT NOSED OVER AFTER TOUCHING DOWN. METALLURGICAL TESTING REVEALED THAT THE CRANKSHAFT HAD EXPERIENCED FATIGUE FAILURE. THE ENGINE HAD BEEN INSTALLED ON A FIELD APPROVAL. THE PROPELLER/ENGINE COMBINATION INSTALLED IN THIS AIRCRAFT HAD NOT BEEN TESTED OR APPROVED FOR THIS, OR ANY OTHER, INSTALLATION.
FATIGUE FAILURE OF THE CRANKSHAFT. FACTORS INCLUDE NON SUITABLE TERRAIN FOR A FORCED LANDING AND AN IMPROPER PROPELLER.
Source: NTSB Aviation Accident Database
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