N22704
BELL 206B-III
THE ACFT EXPERIENCED AN ENG FAILURE DURING A SLING LOAD PICK UP ON AN OFFSHORE PLATFORM. DURING THE AUTOROTATION, THE LEFT SKID AND FLOAT STRUCK A HANDRAIL ON THE RIG AND SEPARATED. THE ACFT IMPACTED THE WATER, NOSE LOW, AND ROLLED OVER AS A RESULT OF THE SEPARATED FLOAT. INVESTIGATION REVEALED THAT THE ENG FAILURE WAS A RESULT OF A 6TH STAGE COMPRESSOR WHEEL FATIGUE FAILURE. THE WHEEL FATIGUE ORIGINATED AT A CASTING INCLUSION THAT HAD NOT BEEN DETECTED DURING THE MANUFACTURING PROCESS.
A COLLISION BETWEEN THE AIRCRAFT AND THE PLATFORM DURING THE EMERGENCY AUTOROTATION WHICH CAUSED THE LEFT SKID AND FLOAT TO SEPARATE AND DESTABILIZED THE AUTOROTATION. THE COLLISION WAS PROBABLY UNADOIDABLE DUE TO THE MANEUVER THAT WAS BEING CONDUCTED AT THE ONSET OF THE EMERGENCY. THE EMERGENCY LANDING WAS ATTEMPTED FOLLOWING AN ENGINE FAILURE THAT WAS THE RESULT OF A TOTAL COMPRESSOR FAILURE. THE COMPRESSOR FAILURE WAS CAUSED BY A FATIGUE FAILURE OF THE SIXTH STAGE WHEEL WHICH SEPARATED. THE FAILURE WAS INITIATED DUE TO A CASTING INCLUSION IN THE WHEEL WHICH WAS NOT DETECTED DURING THE MANUFACTURING PROCESS.
Source: NTSB Aviation Accident Database
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