LACEY TOWNSHIP, NJ, USA
N21FL
AGUSTA A109A MKII
AS THE HELICOPTER WAS IN CRUISE FLT AT AN ALT OF 2200' MSL, A PORTION OF ONE OF THE MAIN ROTOR BLADES SEPARATED. THE SUBSEQUENT IMBALANCE RESULTED IN SEPARATION OF THE TRANSMISSION & MAIN ROTOR ASSEMBLY FROM THE HELICOPTER. THE HELICOPTER THEN CRASHED IN AN UNCONTROLLED DESCENT. A METALLURGICAL EXAM OF THE SEPARATED BLADE REVEALED THAT IT HAD FAILED FROM FATIGUE. THE FRACTURE HAD INITIATED AT A MANUFACTURING INDUCED SCRATCH IN THE SPAR OF THE BLADE. THE SCRATCH WAS ON THE INNER SURFACE OF THE SPAR AT BLADE STATION 2825 (IN MILLIMETERS), NEAR THE LEAD BALANCE WT. IT WAS IN LINE WITH THE EDGE OF THE ADHESIVE FILET. THERE WAS EVIDENCE THAT THE CRACK ORIGINATED WHERE A SHARP TOOL WAS USED TO TRIM THE EDGE OF THE ADHESIVE FILET. THE BLADE FRACTURED AFTER 922 HRS OF OPERATION.
IN-FLIGHT SEPARATION OF A MAIN ROTOR BLADE DUE TO FATIGUE FAILURE OF THE MAIN ROTOR BLADE SPAR, WHICH ORIGINATED AT A MANUFACTURING INDUCED SCRATCH (TOOL MARK) THAT WAS THE RESULT OF INADEQUATE QUALITY CONTROL.
Source: NTSB Aviation Accident Database
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