CHANDLER, AZ, USA
N89678
COBB INTL EXEC 90
THE HELICOPTER'S ENGINE FAILED WHILE ON THE CROSSWIND LEG. THE SURROUNDING TERRAIN WAS CONGESTED FORCING THE PILOT TO LAND IN AN AREA WHICH WAS DOWNWIND. THE HELICOPTER NOSED DOWN ON LANDING IN THE SOFT TERRAIN. EXAMINATION OF THE ENGINE DISCLOSED THAT AN INTAKE VALVE FAILED AND LODGED IN THE PISTON. METALLURGICAL EXAMINATION REVEALED THAT THE VALVE STEM FAILED IN FATIGUE. THE FATIGUE WAS PRECIPITATED BY THE MANUFACTURER'S IMPROPER QUALITY CONTROL WHICH FAILED TO ASSURE THAT THE VALVE WAS GROUND BEFORE IT WAS PLATED.
THE MANUFACTURER'S INADEQUATE QUALITY CONTROL WHICH RESULTED IN THE FATIGUE OF THE VALVE STEM. THE SOFT TERRAIN CONTRIBUTED TO THIS ACCIDENT.
Source: NTSB Aviation Accident Database
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